Philosophiae Doctor

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How to cite this thesis

Surname, Initial(s). (2012) Title of the thesis or dissertation. PhD. (Chemistry)/ M.Sc. (Physics)/ M.A. (Philosophy)/M.Com. (Finance) etc. [Unpublished]: University of Johannesburg. Retrieved from: https://ujdigispace.uj.ac.za (Accessed: Date). DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH AFRICA.

Mathew J Ross

A Thesis submitted in fulfilment of the requirements for the Degree

PHILOSOPHIAE DOCTOR

In Aquatic Health

In the Department of Zoology, Faculty of Science

at the

University of Johannesburg

Supervisor: Professor Victor Wepener

May 2015 TABLE OF CONTENTS

LIST OF TABLES ...... VII LIST OF FIGURES ...... IX ACKNOWLEDGEMENTS ...... XIV ACRONYMS AND ABBREVIATIONS ...... XVI SUMMARY ...... XVII

CHAPTER 1: INTRODUCTION AND LITERATURE REVIEW ...... 1

1.1. Background & Chapter Overview ...... 2 1.2. Fish Migrations ...... 3

1.2.1. Types of migrations ...... 3 1.2.2. Reasons for migrations ...... 5 1.2.2.1. Active migrations ...... 5 1.2.2.2. Passive migrations ...... 7 1.3. Barriers to Migration & Implications of River Fragmentation ...... 8

1.3.1. Types of migratory barriers ...... 8 1.3.2. Implications of barriers on fish migration...... 9 1.3.3. Fish migratory barriers and the South African perspective ...... 12 1.4. What are Fishways? ...... 22

1.4.1. Historical overview of the development of the concept of fishways ...... 22 1.4.2. Types of fishways ...... 24 1.4.2.1. Pool-type fishways ...... 26 1.4.2.2. Baffle fishways ...... 33 1.4.2.3. Fish locks, lifts and elevators ...... 34 1.4.2.4. Natural and rock-ramp fishways ...... 36 1.4.2.5. Eel fishways (eelways) ...... 39 1.4.2.6. Trap and transport fishways ...... 39 1.4.3. Fishways around the world ...... 40 1.4.3.1. North America, Canada & Alaska ...... 40 1.4.3.2. South America ...... 41 1.4.3.3. European Union ...... 42 1.4.3.3.1. United Kingdom ...... 42 ii | P a g e TABLE OF CONTENTS

1.4.3.3.2. Western Europe ...... 43 1.4.3.3.3. Spain and Portugal ...... 44 1.4.3.4. Japan and China ...... 45 1.4.3.5. India and Pakistan ...... 46 1.4.3.6. Australia ...... 46 1.4.3.7. New Zealand ...... 48 1.4.3.8. Africa ...... 48 1.4.3.8.1. North and Central Africa ...... 48 1.4.3.8.2. Southern Africa ...... 48 1.4.3.8.2.1. Pool and weir-type fishways ...... 51 1.4.3.8.2.2. Vertical slot fishways in South Africa ...... 55 1.4.3.8.2.3. Natural bypass channel ...... 57 1.4.3.8.2.4. Combinations of fishway types ...... 59 1.5. Freshwater Fish of Southern Africa...... 61 1.6. Hypothesis & Research Questions ...... 63

1.6.1. Research question ...... 63 1.6.2. Hypotheses ...... 63 1.6.4. Specific research objectives ...... 64 1.6.5. Thesis outline ...... 65 1.7. References ...... 66

CHAPTER 2: LABORATORY TRIAL TESTING OF THE VERTICAL SLOT FISHWAY USING INDIGENOUS FISH SPECIES UNDER STEEPER GRADIENTS ...... 78

2.1. Introduction ...... 79

2.1.1. Choice of experimental fishway design ...... 81 2.1.2. Hydraulic characteristics and concepts within a vertical slot fishway ...... 83 2.1.3. Biological aspects pertaining to the vertical slot fishway ...... 87 2.1.4. Aims and objectives ...... 90 2.2. Materials & Methods ...... 92

2.2.1. Laboratory design...... 92 2.2.1.1. Environmentally controlled room ...... 92 2.2.1.2. Housing system ...... 92 2.2.2. Experimental fishway channel specifications and variations ...... 97 2.2.2.1. Standard vertical slot ...... 97 2.2.2.1. Experimental fishway variations ...... 98 2.2.3. Fish species ...... 98 2.2.4. Acclimation of fish ...... 99 2.2.5. Project plan and experimental design ...... 100 2.2.5.1. Experimental protocol ...... 100 2.2.5.1.1. Stimulation phase ...... 100 2.2.5.1.2. Experimental phase ...... 101

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2.3. Results & Discussions ...... 102

2.3.1. The stimulation phase ...... 102 2.3.1.1. Manipulation of temperature to induce migrational behaviour ...... 102 2.3.1.2. Manipulation of flow and other factors to induce migrational behaviour ...... 102 2.3.3. Experimental hydraulic conditions of fishway channel ...... 103 2.3.4. Results from experimental procedures ...... 104 2.3.4.1. Experiment 1: Standard vertical slot ...... 106 2.3.4.2. Experiment 2: Vertical slot with 100 mm sills ...... 110 2.3.4.3. Experiment 3: Vertical slot with 100 mm sills and pebble substrate ...... 113 2.4. Conclusions & Recommendations ...... 115 2.5. References ...... 117

CHAPTER 3: FIELD TRIAL TESTING USING AN EXPERIMENTAL IN SITU SCALE MODEL VERTICAL

SLOT FISHWAY CHANNEL TO VALIDATE AND SUPPLEMENT LABORATORY EXPERIMENTAL DATA ...... 121

3.1 Introduction ...... 122

3.1.1. Background ...... 122 3.1.2. Aims and objectives ...... 124 3.2. Site Selections & characteristics ...... 124

3.2.1. Sites in the Vaal River ...... 125 3.2.2. Sabie River ...... 128 3.3. Materials & Methods ...... 132

3.3.1. Description of the experimental fishway setup and design ...... 132 3.3.2. Collection and acclimation of fish ...... 135 3.4. Results & Discussions ...... 135

3.4.1. Hydraulic conditions of the experimental channel ...... 135 3.4.2. Results of field trial replicates ...... 136 3.4.2.1. Vaal River...... 136 3.4.2.1.1 Trial replicate 1 ...... 138 3.4.2.1.2. Trial replicate 2.1 ...... 140 3.4.2.1.3. Trial replicate 2.2 ...... 142 3.4.2.2. Sabie River ...... 143 3.4.2.2.1. Trial replicate 1A ...... 144 3.4.2.2.2. Trial replicate 1B ...... 146 3.4.2.2.3. Trial replicate 2 ...... 146 3.4.2.2.4. Trial replicate 3 ...... 147 3.4.2.2.5. Trial replicate 4 ...... 149 3.4.2.2.6. Trial replicate 5 ...... 152 3.4.2.2.7. Trial replicate 6 ...... 153

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3.4.3. Summary of field survey results ...... 155 3.4.4. General observations and other applicable information...... 162 3.4.4.1. Migratory cues, timing and reasons for migrations ...... 162 3.4.4.2. Migratory behaviour, swimming and jumping behaviour ...... 164 3.4.4.3. Age class of migratory fish ...... 167 3.5. Conclusions & Recommendations ...... 169 3.6. References ...... 172

CHAPTER 4: CASE STUDY & LESSONS LEARNT ...... 175

4.1. Introduction ...... 176 4.2. Locality & Hydrological Characteristics of the River Reach ...... 178 4.3. Factors Affecting Fish Migrations within the River Reach...... 183 4.4. Fish Community Structures within the River Reach ...... 185 4.5. Design Rationale & Specifications of the Fishway ...... 188

4.5.1. General description of gauging weir and fishway orientation ...... 188 4.5.2. Fishway specifications ...... 193 4.5.3. Fishway hydraulics ...... 199 4.6. Monitoring of the Fishway ...... 200

4.6.1. Fishway survey orientation ...... 200 4.6.2. Sampling methodologies ...... 201 4.7. Fish Assemblages in the River Reach ...... 202 4.8. Assessment of Fishway Functionality ...... 203

4.8.1. Survey 1 ...... 204 4.8.2. Survey 2 ...... 206 4.8.3. Survey 3 ...... 207 4.8.4. General observations of fishway functionality ...... 210 4.8.5. Data comparisons to similar studies ...... 212 4.9. Conclusions & Lessons Learnt ...... 215 4.10. References ...... 216

CHAPTER 5: GENERAL CONCLUSIONS AND RECOMMENDATIONS ...... 219

5.1. Conclusions ...... 220 5.2. Implementation of Fishways to Mitigate Current and Emerging Major Threats to Natural Fish Passage in South African Rivers ...... 227

5.2.1. Hydropower developments ...... 227 5.2.2. Flow-gauging weirs ...... 228 5.3. Recommendations and Factors to Consider for Optimal Fishway Design ...... 230

5.3.1. Economic considerations that influence design ...... 230 5.3.2. Biological considerations that influence design ...... 231 5.3.3. Design guidelines and considerations...... 231 v | P a g e TABLE OF CONTENTS

5.3.3.1. Length of channel ...... 232 5.3.3.2. Resting areas ...... 232 5.3.3.3. Setting maximum hydraulic parameters ...... 234 5.3.3.4. Fishway channel dimensions ...... 235 5.3.3.5. Submerged flow conditions ...... 235 5.3.3.6. Minimum flow depth ...... 236 5.3.3.7. Channel substrate ...... 236 5.3.3.8. Placement of the fishway entrance ...... 237 5.3.3.9. Dealing with floating debris, siltation and management of the fishway237 5.3.3.10. Modifications to standard vertical slot fishway ...... 238 5.4. References ...... 239

APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SOUTH AFRICA, KNOWLEDGE BASE AND ASSESSMENT OF FUNCTIONALITY (UPDATED FROM BOK ET AL., 2007)...... 240 APPENDIX B: – ABBREVIATIONS OF RELEVANT FISH SPECIES MENTIONED IN THIS STUDY ...... 253

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LIST OF TABLES

Table 1-1: The Cape Coastal migratory regions in South Africa according to migratory behaviour and swimming ability of migratory biota present (taken from Bok et al., 2004)...... 58 Table 1-2: Inland migratory regions and main migratory groups and species (taken from Bok et al., 2004)...... 59 Table 2-1: The dimensions and generalised standard testing variations of the experimental fishway channel...... 92 Table 2-2: Fish species from the Vaal River system used during experimental trials of the vertical slot fishway channel...... 99 Table 2-3: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:3 at varying discharge rates, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 107 Table 2-4: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:4 at varying discharge rates, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 108 Table 2-5: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:5 at varying discharge rates, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 109 Table 2-6: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:3 at varying discharge rates with the placement of 100 mm sills in each slot, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 112 Table 2-7: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:4 at varying discharge rates with the placement of 100 mm sills in each slot, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 112 Table 2-8: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:5 at varying discharge rates with the placement of 100 mm sills in each slot, showing the average (mean) values (percentage of the test population) and standard deviation values from triplicate experimental procedures...... 113 Table 3-1: Sampling sites selected in the Vaal River for the various field assessments...... 127 Table 3-2: Sampling sites selected in the Sabie River for the various field assessments...... 129 Table 3-3: Summary of the hydraulic characteristics of the experimental vertical slot fishway channel under field conditions for both the Vaal River and Sabie River experiments...... 136 Table 3-4: Fish species to successfully negotiate the vertical slot type fishway at the given gradients during experiments at the Vaal River. The standard lengths (SL) (mm) ranges are given in brackets. A summary of the hydraulic conditions at the given gradients is also provided...... 137 Table 3-5: Fish species to successfully negotiate the vertical slot type fishway at the given gradients during experiments at the Sabie River for the first of the two field surveys. The standard lengths (SL) (mm) ranges are given in brackets. A summary of the hydraulic conditions is also provided...... 145

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Table 3-6: Fish species to successfully negotiate the vertical slot type fishway at the given gradients during trial replicates at the Sabie River for the second of the two field surveys. The standard lengths (SL) (mm) ranges are given in brackets. A summary of the hydraulic conditions is also provided...... 148 Table 3-7: Summary of the channel gradients successfully negotiated by the fish species and the associated hydraulic conditions...... 160 Table 3-8: Fishway channel gradient and how it translates to percentage slope...... 163 Table 3-9: Summary of the visual observations at the time of the field survey...... 164 Table 4-1: Details of the various artificial migratory barriers located between the Orange River mouth and Blouputs Weir...... 185 Table 4-2: All fish species recorded from the Lower Orange River that would be impacted by the establishment of a migratory barrier (from Benade, 2003), together with their recommended hydraulic limits (from Bok et al., 2007)...... 186 Table 4-3: Reference species Frequency of Occurrence (FROC) (Kleynhans et al., 2007) relevant to the river reach including Blouputs Weir and downstream...... 188 Table 4-4: Hydraulic conditions within the fishway at the sampling times...... 199 Table 4-5: The fish species sampled during the time of the fishway survey, numbers of individuals, size classes and habitat type from the area immediately downstream of Blouputs Weir...... 203 Table 4-6: Results of Survey 1 (26 February 2014) at the Blouputs fishway...... 205 Table 4-7: Results of Survey 2 (25 April 2014) at the Blouputs fishway...... 208 Table 4-8: Results of Survey 3 (11 September 2014) at the Blouputs fishway...... 209 Table 4-9: Comparisons of some key design features between Xikundu and Blouputs fishways. 213 Table 5.1: Proposed design specifications and limitations for vertical slot fishways...... 234

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LIST OF FIGURES

Figure 1-1: Active fish migrations, dominated by Cyprinidae (top and bottom left) and Mochokidae (bottom right) species that have been observed in the field during the course of this study (Sabie River, Kruger Gate Weir, Nov, 2004)...... 7 Figure 1-2: Hartbeespoort Dam wall on the Crocodile (west) River...... 13 Figure 1-3: A sharp crest flow-gauging weir on the Vaal River...... 15 Figure 1-4: A crump flow-gauging weir at Sendelingsdrift (Blouputs) on the Orange River...... 15 Figure 1-5: A flow-gauging weir at Goosebay on the Vaal River...... 16 Figure 1-6: A crump flow-gauging weir on the Sabie River located downstream of the Kruger Gate...... 16 Figure 1-7: A flow-gauging weir on the Crocodile (west) River...... 17 Figure 1-8: A flow-gauging weir at Klipplaatdrift on the Vaal River. Under flood conditions such as at the time of taking this photograph, the weir tends to drown out and allows a degree of freedom to negotiate across it by stronger-swimming species...... 18 Figure 1-9: An irrigation diversion weir at Neusberg on the Orange River...... 18 Figure 1-10: A poorly-designed low-level vehicle crossing on the Jukskei River in Midrand that created migratory barriers to fish...... 19 Figure 1-11: An abstraction weir on the Jukskei River in Midrand that incorporates a low-level crossing for vehicles. No provision for fish passage was provided and therefore the structure creates a migratory barrier...... 19 Figure 1-12: A weir constructed on the headwaters of the Crocodile (west) River as part of historical irrigation schemes for the area which has since been abandoned...... 20 Figure 1-13: A low-level causeway at an abandoned trout hatchery located at the headwaters of the Magalies River...... 21 Figure 1-14: A diagram of pool and weir fishways (taken from Katopodis, 1992)...... 28 Figure 1-15: Various views of a notched pool and weir fishway with submerged orifices (three- dimensional modelling developed by Ansara Architects)...... 30 Figure 1-16: A schematic representation of a vertical slot fishway (not to scale) (three- dimensional modelling developed by Ansara Architects)...... 32 Figure 1-17: A schematic representation of a plain Denil fishway. The diagram on the right presents the channel with the side wall removed to allow for a clear view of the shape of the baffles...... 34 Figure 1-18: A schematic representation of a lock fishway (taken from Thorncraft & Harris, 2000)...... 35 Figure 1-19: A schematic representation of trap-and-transport fishway (taken from Thorncraft & Harris, 2000)...... 36 Figure 1-20: A schematic representation of a rock-ramp fishway (taken from Thorncraft & Harris, 2000)...... 37 Figure 1-21: A schematic representation of a natural flow-like fishway (taken from Thorncraft & Harris, 2000)...... 38 Figure 1-22: Xikundu Weir fishway (photo courtesy of Dr P. Fouché)...... 52 Figure 1-23: Kanniedood Dam on the Shingwedzi River in the Kruger National Park (left), showing the notched pool and weir fishway located on the left bank (right)...... 54 ix | P a g e LIST OF FIGURES

Figure 1-24: A notched pool and weir fishway located on the Komati River in Komatiepoort...... 54 Figure 1-25: The vertical slot fishway that aids in allowing fish freedom of passage across Neusberg abstraction weir...... 56 Figure 1-26: Examples of derivatives of the vertical slot fishway design located on various rivers throughout South Africa: Left – Goosebay Fishway (Vaal River); Right – Fishway at the Lower Sabie Weir ...... 57 Figure 1-27: The natural bypass channel constructed on the Sabie River, downstream of the Lower Sabie Weir...... 58 Figure 1-28: An informal pool and weir fishway design constructed on the Sabie River, where a series of larger pools (pre-barrages) were constructed to allow for progressive gain in height to help fish negotiate across the weir...... 59 Figure 1-29: A diagrammatic plan for the fishway that has since been constructed at Klipplaatdrift on the Vaal River following upgrading of the associated weir (compliments of DWA)...... 60 Figure 2-1: The dimensions of a single pool of the experimental vertical slot fishway channel used in this study (adapted from Larinier et al., 2002). All the dimensions of the fishway are given relative to the slot opening width, identified as “A” in figure and the dimensions of each successive pool are repetitious of the one that precedes it...... 79 Figure 2-2: Flow conditions in a vertical slot fishway (adapted from Bok et al., 2007)...... 81 Figure 2-3: Different hydraulic characteristics of housing system; with areas of high turbulence (top left and right) and quieter areas of low turbulence (bottom left and right)...... 93 Figure 2-4: Filtration system and water pumps used to enhance water flow through the system. ... 89 Figure 2-5: Biological filter canisters with ‘BioBalls®’ filter medium...... 89 Figure 2-6: Valve position selector for system maintenance...... 95 Figure 2-7: In-line ball valves that control the direction and volume of water passing either into the system channel or the fishway channel...... 95 Figure 2-8: Fishway headway tank emptying into the first bucket of the fishway channel...... 96 Figure 2-9: Effects on discharge Q (m3/s), water velocity Vslot (m/s), pool volume Vol (m3) and 3 turbulence levels Pv (watts/m ) for the standard vertical slot type of fishway at a gradient of 1:3, 1:4 and 1:5 as the water head (flow into the fishway) is increased. The shaded areas indicate the hydraulic conditions before the discharge is sufficient to support submerged flow conditions. The discharge, water velocity and volume variables are given on the primary Y-axis and turbulence values given on the secondary Y-axis...... 99 Figure 2-10: Species success rates (L. aeneus, L. capensis, T. sparrmanii, A. sclateri and B. anoplus) using a standard vertical slot fishway channel at three different gradients at given discharge rates under laboratory conditions. Corresponding turbulence (Pv) values are given on the secondary Y-axis...... 99 Figure 2-11: Hydraulic variables for the standard vertical slot type of fishway with the placement of a 100 mm sill in each slot opening between pools at a gradient of 1:3, 1:4 and 1:5. The shaded areas indicate when the discharge volume is not sufficient to support submerged flow conditions...... 111 Figure 2-12: Results of the experiments using a vertical slot fishway channel with the addition of 100 mm sills in each slot opening between all successive pools at three different gradients at varying discharges under laboratory conditions. Fish species abbreviations are given in Appendix B ...... 111 Figure 3-1: Localities of the survey sites on the Vaal River...... 125 Figure 3-2: The flow-gauging structure Vaal River at the Vischgat (Engelbrechtsdrift) site that presents a migration barrier to fish within the system...... 126 x | P a g e LIST OF FIGURES

Figure 3-3: Typical habitat at the Vaal River at the Vischgat (Engelbrechtsdrift) site...... 127 Figure 3-4: Typical habitat at the Vaal River at the Eendekuil site...... 128 Figure 3-5: Localities of the survey sites on the Sabie River...... 129 Figure 3-6: DWS weir (X3H021) in Sabie River located downstream of Kruger Gate...... 130 Figure 3-7: Congregation of a diversity of fish species at the Sabie River site opportunistically trying to negotiate passage upstream across the weir within peripheral zones of the watercourse...... 130 Figure 3-8: The basic experimental setup of the vertical slot fishway utilised for the field experiments, showing the headway tank connected to the lower collection tank, with a water pump that circulates water through the channel...... 132 Figure 3-9: The relative dimensions of a single pool of the experimental vertical-slot fishway channel used in this study (adapted from Larinier et al., 2002). Flow direction is from right to left. All the dimensions of the fishway are given relative to the slot opening width, identified as “A” in figure and the dimensions of each successive pool are repetitious of the one that precedes it...... 133 Figure 3-10: Where site conditions allowed for it, the end of the experimental channel was placed directly into the river...... 134 Figure 3-11: Results of trial replicate 1 at the Vaal River (Eendekuil). Fish species abbreviations are given in Appendix B...... 139 Figure 3-12: Results of trial replicate 2.1 at the Vaal River (Vischgat). Fish species abbreviations are given in Appendix B...... 140 Figure 3-13: Results of trial replicate 2.2 from the Vaal River at Vischgat. Fish species abbreviations are given in Appendix B...... 142 Figure 3-14: Results of trial replicate 3, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B...... 149 Figure 3-15 Results of trial replicate 4A, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B...... 150 Figure 3-16: Results of trial replicate 4B, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B...... 151 Figure 3-17: Results of trial replicate 5, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B...... 153 Figure 3-18: Results of trial replicate 6, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B...... 154 Figure 3-19: Summary of the field tests of the experimental vertical slot fishway for each individual species for both the Vaal River and Sabie River field surveys. Only the gradients applicable to the species tested for are indicated. Fish species abbreviations are given in Appendix B...... 158 Figure 3-20: Summary of the data collected from trial testing of the vertical slot fishway under field conditions, showing the channel gradients that showed the most success rates and the percentage of the test population of each species that successfully negotiated the channel at the given gradient. A limit of 70% of the test population to successfully negotiate the channel is thought to be the limit in considering if the data are conclusive. Fish species abbreviations are given in Appendix B...... 161

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Figure 3-21: Flows measured at the Kruger Gate Weir for the Sabie River for the time preceding the time of the first field survey (indicated by the arrow) as well as immediately afterwards (taken from DWAF, 2005)...... 163 Figure 3-22: Labeo capensis adults attempting to negotiate upstream across the weir...... 164 Figure 3-23: Labeo molybdinus successfully negotiating a small vertical wall below the weir, as referred to in Table 3-8...... 166 Figure 3-24: Chiloglanis swierstrai individuals observed negotiating vertical concrete wall at the base of a weir. Individuals were observed to often negotiate passage on the periphery of the flowing areas as referred to in Table 3-8...... 166 Figure 3-25: Fish opportunistically congregating along the wetted periphery of the watercourse as it flowed over the weir as they attempt to negotiate passage across the weir. Labeobarbus molybdinus, B. viviparus and B. trimaculatus dominated the species composition here...... 167 Figure 4-1: Relative localities of the various artificial and natural migratory barriers located between the Orange River mouth and Blouputs Weir (western region)...... 178 Figure 4-2: Relative localities of the various artificial and natural migratory barriers located between the Blouputs Weir and the source (eastern region)...... 179 Figure 4-3: Average monthly flow discharges for the Orange River at the DWS Neusberg Weir for the period August 2009 to April 2014...... 182 Figure 4-4: Proportion of time that the river flow rate is expected to exceed 320 m3/s as a proportion of when it is expected to be less than 320 m3/s (based on data for the Orange River at the DWS Neusberg Weir [DWA, 2012]). This is an indication of the time proportions when the gauging weir tends toward drowned-out hydraulic conditions and will no longer present as a migratory barrier to fish...... 183 Figure 4-5: Aerial view of the fishway at Blouputs Weir to show orientation (Google Earth®, 2014). This aerial photograph was taken during the construction phase of the weir and therefore only the high crest of the weir and the fishway were functional at the time. Only the fishway and the high crest weir are visible...... 189 Figure 4-6: View of the Blouputs fishway in the foreground and the Blouputs Weir from the southern bank...... 190 Figure 4-7: A top view of the design specification of the fishway implemented at Blouputs (provided by DWS, Hydrological Services, Pretoria)...... 191 Figure 4-8: A side view of the design specification of the fishway implemented at Blouputs (provided by DWS, Hydrological Services, Pretoria)...... 192 Figure 4-9: Three-dimensional figure of the fishway at Blouputs (not to scale) (three-dimensional modelling developed by Ansara Architects)...... 193 Figure 4-10: The entrance of the fishway showing the deflection wall that directs overflow water toward the entrance to increase attraction flows toward the entrance to help fish to locate it...... 196 Figure 4-11: The vertical slot between two successive pools showing the sloped upper surface of the sill...... 197 Figure 4-12: Top view of the Blouputs fishway showing the upper and lower levels of pools...... 198 Figure 4-13: View of the larger resting pool that incorporates the second turning point of the fishway...... 198 Figure 4-14: Hydraulic characteristics of the fishway at Blouputs, showing hydraulic conditions during survey periods and indicating the discharge volume where submerged flow conditions occur. The labels correspond to hydraulic conditions at the survey times (Table

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4-4). An indication of the ecological functionality of the fishway is provided, showing that the fishway gains functionality as the discharge increases...... 200 Figure 4-15: Diagrammatic representation of the fishway at Blouputs Weir showing pool numbering (three-dimensional modelling developed by Ansara Architects)...... 201 Figure 4-16: The proportion of fish species sampled within the fishway during February 2014. ... 205 Figure 4-17: The proportion of individuals of the fish species sampled during February 2014 within the fishway that were in the upper level of pools in relation to those surveyed within the lower level of pools...... 205 Figure 4-18: The proportion of fish species sampled within the fishway during April 2014...... 208 Figure 4-19: The proportion of individuals of the fish species sampled during April 2014 within the fishway that were in the upper level of pools in relation to those surveyed within the lower level of pools...... 208 Figure 4-20: The proportion of fish species sampled within the fishway during September 2014. 209 Figure 4-21: The proportion of individuals of the fish species sampled during September 2014 within the fishway that were in the upper level of pools in relation to those surveyed within the lower level of pools...... 209 Figure 4-22: Flow rate ratio between the high crest and low crest weir as the overall river flow rate increases...... 212

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ACKNOWLEDGEMENTS

Funding for the project was provided by the Water Research Commission, who also sponsored a presentation of the project at an international conference in Brisbane, Australia.

The facilities to house the laboratory experiments, vehicles and equipment required for field testing was provided by the University of Johannesburg’s Research Aquarium.

I would like to acknowledge and thank the following people who formed an integral role in the overall project:

 Dr Pieter Wessels for freely providing technical engineering support to a “non- technical fish biologist” with repetitive patience and kindness so that I could gain a better understanding of hydraulic principles, calculations and flow dynamics. This has allowed me to have a solid foundation on which to base my findings and results;  Mr Riaan van der Walt, who works together with Dr Wessels at DWS Hydrological Services, and who was always willing to provide information, photographs and to answer questions;  Prof Victor Wepener for endeavouring to act as my supervisor, for providing answers to questions that were asked numerous times and for providing the much- needed back-up support to get this PhD completed;  Dr Pieter Kotze who was the initial project leader of the biological components of the original WRC project. Thank you for your support during field surveys, and guidance in developing the structure of the project. My initial practical knowledge and exposure to aquatic monitoring was gained through us working closely together and my initial love for fish ecology was inspired by you and Brenton (Mr B Niehaus);  Dr Jan Rossouw, Dr Anton Bok, Dr Andrew Deacon, Dr Ralph Heath and Prof Gert Steyn for technical assistance to the project;  Dr Andrew Deacon, Dr Jan Rossouw, Dr Pieter Kotze, Mr Brenton Niehaus, Dr Gordon O’Brien, Dr Richard Greenfield and Dr Tahla Ansara-Ross for helping with field work and fish collection components;

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 Mr Piet Muller (of GDARD) and the GDARD technical field team for helping collect fish from the Vaal, Suikerbosrand and Wilge rivers;  Family and friends for their never-ending enquiries of “is your PhD finished yet?” Your sacrifices over the years, patience, support and belief in me throughout all these years is greatly appreciated.

This thesis is the culmination of many years of attending university that would not have initially been possible if it were not for the generous financial support of my late uncle, Chappie (Dr Walter Orr). For where I find myself today, I remain most grateful.

My wife, Tahla, who has been an unfailing, understanding and supportive partner throughout all the lonely nights, early mornings and my absent weekends due to the perpetual “working on my PhD” and for entertaining my child-like exploratory enthusiasm, to the extent of even cutting our honeymoon short to accommodate the project. You have acted as a field assistant, and having been through all this before, was able to act as a mentor, part supervisor, advisor, editor, proof reader, motivator … and disciplinarian. Looking after our daughters, Zoë and Ella, is more than a full time job for you, yet there was always time for helping me out. I appreciate you, I admire you and I could not have done this without you.

xv | P a g e ACRONYMS AND ABBREVIATIONS

ACRONYMS AND ABBREVIATIONS

DEA Department of Environmental Affairs

DWA Department of Water Affairs

DWAF Department of Water Affairs and Forestry

DWS Department of Water and Sanitation

EIA Environmental Impact Assessment

FRAI Fish Response Assessment Index

FROC Frequency of Occurrence

GIS Geographical Information System

IWRM Integrated Water Resource Management (

KNP Kruger National Park

LHDA Lesotho Highlands Development Authority

LHWP Lesotho Highlands Project

NEMA National Environmental Management Act

ND No Data

NWA National Water Act

RA Relative abundance

RBM Richards Bay Minerals

SF Submerged flow

SL Standard Length

TL Total Length

UJ University of Johannesburg

USACE U.S. Army Corps of Engineers

WMA Water Management Areas

WRC Water Research Commission

xvi | P a g e SUMMARY

SUMMARY

Fish migrate for a multitude of reasons. Perhaps the most well-known, and most documented, example of fish migrations is the upstream annual mass movement of the anadromous salmonid species of northern hemisphere temperate systems. This migration is for habitat and resource exploitation for cyclic breeding purposes, and is the most well- known reason for fish migrations worldwide, resulting in often-spectacular mass movements of both potadromous and diadromous fish to locate upstream-located spawning habitat. There are other migrational movements that require longitudinal and lateral connectivity of watercourses, which include the need to escape unfavourable local conditions, predator evasion, dispersal of species, feeding and seeking refuge. The ultimate long-term need for maintaining longitudinal connectivity of watercourses and freedom of movement of aquatic organisms is the overall maintenance of genetic diversity.

With this knowledge, the maintenance of migratory freedom to the ongoing conservation of fish populations, not only in South Africa but worldwide, has been identified as a leading conservation concern. This has led to an increasing global interest to develop fishways with improved functionality. The degree of functionality is dependent on providing hydraulic parameters at a particular migratory barrier that can be successfully overcome by the swimming abilities of the target population of fish species of a specific river system. An understanding is therefore required of these hydraulic parameters, which fish are capable of negotiating passage through without expenditure of undue energy. Internationally, the focus of fishway research has been on the preservation of the socio-

xvii | P a g e SUMMARY economic salmonid species, with little regard being given to the conservation of fish species purely from an ecosystem health perspective. It is only within the recent past that focus is beginning to shift to n holistic ecosystem conservation approach, with fishways being developed that cater for a wider diversity of fish species. In the early days of fishway development, South Africa relied on international literature which was, at the time, mainly focused on developing fishways with salmonids as the target group. This led to many dysfunctional fishways being developed throughout South Africa that did not offer physical or hydraulic conditions that catered for local fish species. There is a trend throughout South Africa to focus on developing more ecologically sound fishways, but South Africa trails approximately 20 years behind countries such as Canada, France and the northern regions of the United States of America. Therefore, although there is a growing trend to develop better-performing fishways throughout South Africa, the knowledge base and data on the hydraulic requirements of the fish, as well as expertise in the field, are largely lacking.

The main research question of this thesis and therefore the central theme is:

What are the conservative limits to the migratory potentials of the selected fish species in terms of swimming and jumping abilities, and how will this help in determining the hydraulic parameter limits when designing and constructing a fish bypass facility?

A further research question is also included:

Can a single fishway be sufficiently modified to increase efficiency in passing fish, eels and aquatic macro-invertebrates that also require migratory freedom across instream river barriers, whilst still remaining cost-effective and practical for construction?

xviii | P a g e SUMMARY

The introductory chapter (Chapter 1) evaluates the present state of knowledge of fishways and fish migration both globally and in South Africa. To place this Thesis in context and provide a focus for the review, the chapter starts with an examination of the processes and reasons for migration and the importance of maintaining migratory freedom, the migratory freshwater fish species of South Africa, their distribution and differing migration patterns; and the reasons for decline of these species due to migratory inhibition through river regulating structures. The various types of fishways and their development, both globally and nationally are explored, whilst providing examples of each. A list of known fishways throughout South Africa has been provided, which is an expansion of the knowledge base of existing knowledge. It was found, however, that there are gaps in the knowledge of fishways throughout South Africa, which is largely due to the informal approach of implementation within early development years, the lack of ownership and management of the infrastructure and, in some cases, the lack of follow-up development of non-functional fishways that has led to them becoming redundant.

Through a review of international literature and trends in fishway development on a global scale, the vertical slot fishway was identified as the most versatile fishway design. This is due to it being able to accommodate a wide range of hydraulic conditions (mainly discharge rates) that generally renders the vast majority of other fishway designs ineffective. Flow volume of river systems throughout South Africa is strongly seasonal, with extremes in flow variation often being encountered on an irregular and unpredictable occurrence. The vertical slot design was therefore chosen as the focus of this study as a fishway that could accommodate the variation in flow volume that is experienced by South African river system. The important hydraulic parameters within a fishway to consider when discerning the hydraulic limitations coupled to the swimming abilities of target fish species include the change in water levels between successive pools, water velocity through the opening between successive pools and turbulence levels within each pool. As a fishway is an open channel, flow through it is governed by centre of gravity-driven free- flow conditions, the hydraulic principles and calculations commonly based on Froudian Similitude Laws due to the relations between inertia and gravitational forces of free-flowing water. Therefore, as the discharge rate increases through a vertical slot fishway at a given gradient, the head difference (water levels between successive pools) increases until submerged flow conditions are satisfied, which occurs when the proportion of the head difference to the water depth running through the same slot exceeds 67%. Increased

xix | P a g e SUMMARY discharge rates above this sees the head difference remaining constant, and it is only then that a vertical slot fishway is thought to be hydraulically optimally functional. As the head difference increases with increasing discharge before submerged conditions are reached, an increase in discharge results in an increase in water velocity through the slot, which results in an increase in turbulence experienced within each pool. After submerged flow conditions are satisfied by an adequate discharge rate, an increase in discharge results in no change in head difference between successive pools and therefore no change in the velocity of the water flowing through the slots between pools, and only a minimal increase in turbulence levels. The capacity of a vertical slot fishway to accommodate increasing discharge rates is merely governed by the depth of the channel and slots. These hydraulic principles have been found to reproduce flow dynamics comparably well between model testing and fishway prototype testing and therefore all hydraulic values are directly applicable to full-scale fishways if the dimensions are similarly proportionate between scale models and full-scale versions.

International trends pertaining to the gradient of the vertical slot fishway show that a gradient of less than 1:10 (10%) is normally implemented. Chapter 2 describes an experimental scale model fishway channel that was constructed, which was based on a standard vertical slot design, with the aim of determining if this design could successfully pass a diversity of fish species from the Vaal River system (that represented major migratory groups) at relatively steeper gradients. Under controlled laboratory conditions, an experimental system was constructed that enabled the control of both the channel gradient and discharge rate through the channel. The laboratory-based experiments tested three gradients of the channel, namely 1:3, 1:4 and 1:5, each exposed to discharge rates of 0.0017, 0.0050, 0.0067, 0.0082 and 0.0149 m3/s. The hydraulic characteristics of the experimental channel under these test conditions were calculated and have been provided, which included determining whether the discharge rates satisfied submerged flow conditions under a particular test condition, so that data could be extrapolated to full scale fishways where river flow hydrographs have to be taken into consideration. Ten individuals of Labeobarbus aeneus, Labeo capensis, Barbus anoplus, Tilapia sparrmanii and Austroglanis sclateri were utilised for the laboratory experiments, and all experiments were repeated at least three times. A gradient of 1:3 showed poor passability of the fish, but individuals of L. aeneus, L. capensis and A. sclateri were able to negotiate the channel under these conditions, where turbulence levels were as calculated to be as high as 623

xx | P a g e SUMMARY watts/m3. In order for a fishway to be considered ecologically functional, a minimum percentage success rate of the test population was set. A success rate of above 60% of all species was achieved at a channel gradient of 1:5 with a discharge rate of 0.0067 m3/s, where the water velocity through the slot was calculated at 1.08 m/s and turbulence levels within the pools of 298 watts/m3. A general reluctance to attempt to negotiate the channel was noted during all laboratory-based experiments, which justified making a 60% success rate of the test population a viable reference point. This could be used to extrapolate to natural conditions where the environmental cues to migrate induces far superior swimming abilities in all fish. The limit to ascertaining ecological functionality and performance of a fishway was set at 70% success rate of the fish used for the experiments.

In an attempt to improve the success rate of the fish in negotiating the experimental channel, sills measuring 100 mm were placed in the base of the slot openings. This resulted in premature inundation of the pools under low flow conditions and provided a fixed minimum pool volume that could be advantageous to fish attempting upstream passage through the channel. This also affected the hydraulic characteristics of the channel, with the most noteworthy being a reduced turbulence level experienced by each pool. This modification of the standard vertical slot did improve the performance of the fishway. Under the same conditions as above, where a 60% success rate of the was achieved (gradient of 1:5, discharge of 0.0067 m3/s, and turbulence of 298.1 watts/m3), above 80% success rate was achieved by all species in this test. The placement of the sills in each slot resulted in a decrease in turbulence from 298.1 to 171 watts/m3. Therefore, this modification resulted in an improvement of both hydraulic functionality as well as ecological performance.

The same experimental channel was utilised under field conditions at two localities each along the Sabie and Vaal rivers in order to validate the data gained through laboratory testing, and in an attempt to expand the knowledge base on a greater diversity of species and test conditions. These data are reported on in Chapter 3. Trial replicates were undertaken at a fixed discharge rate of approximately 0.015 m3/s, but various gradients of the channel were experimented with. Two test conditions were utilised, namely placing the entrance of the channel directly in the river at an identified migratory barrier where fish were observed to be congregating where site conditions could accommodate it, or by fixing

xxi | P a g e SUMMARY the channel between two collection tanks in a closed circulation system. In both instances water was pumped into the top headway tank and water flowed through the channel. The standard vertical slot design was used in all cases. A general reluctance of the fish to attempt to negotiate the channel was identified as a limitation to laboratory experimentation of fishway performance, and resulted in the generation of erratic results and performance data. Testing of the channel under field conditions, where fish directly from the river system that were potentially undergoing active migrations could be used, was thought to provide more accurate data on the ecological performance of the experimental channel.

Field trial replicates utilising a diversity of fish species and a variety of channel gradients showed that a diversity of species managed to successfully negotiate channel gradients of as steep as 1:3.15 (31.7% slope), but the channel gradient range that was successfully negotiated by the greatest number of fish was between 1:5 (20%) and 1:10 (10%). There were species that showed that gradients steeper than 1:7.5 were limiting to successful passage through the channel. Field testing of the channel provided the opportunity to increase species-specific knowledge to include a further 19 species (over and above those species utilised for laboratory testing of the channel), and included a further 16 channel gradients. Further data were also generated for the five species that were used for the laboratory testing, which enabled validation of the data gathered in Chapter 2.

The results of the field and laboratory trial testing of the channel relied on the will of the fish to attempt to swim up the channel. Determining whether the limiting factor to the successful negotiation of the channel was the hydraulic conditions at a given gradient or merely a lack of willingness of the fish individuals to attempt passage proved to be a general limitation to the field trial testing of the channel. The resulting data are therefore open to a degree of speculation and their ecological relevance are subject to confidence limits.

The Department of Water Affairs and Sanitation (DWS) identified the need for a flow- gauging weir at Blouputs on the Orange River in the Northern Cape Province during the time of this study, which provided an opportunity to design a fishway based on the data xxii | P a g e SUMMARY gathered during this study. Chapter 4 provides a detailed case study that describes the hydraulic characteristics of the fishway and couples this information to the three field surveys conducted during 2014. The fishway was loosely based on the vertical slot design with various modifications that allowed for a compromise between cost, ease of construction and ecological functionality. The fishway is made up of 17 pools and the channel has two turning points that incorporate double volume pools. The change in water levels between successive pools is 200 mm, which remains constant throughout the fishway. The slot openings are 300 mm wide and are fitted with sills measuring 600 mm high. The length of each pool is 2300 mm and therefore, given an overall slope of the channel of 1:11, the individual pools remain completely inundated with water with no exposed substrate, even under zero flow conditions. The only internal baffles within the channel are those that are orientated perpendicular to the channel, which are aligned within the same plan. The slot opening is within this baffle, which generally runs through the centre of the channel. Although the field surveys did not coincide with times of active fish migrations, preliminary results from the three field surveys showed that both juvenile and adults of a wide diversity of fish, incorporating a diversity of body structures, were able to successfully negotiate passage through this channel. These results, together with the hydraulic analysis of the fishway, indicate that this innovative fishway design is ecologically functional for the target fish species that require migratory freedom within the river reach.

This study set out to determine the viability of implementing a standard vertical slot fishway at steeper gradients under both laboratory and field conditions by determining the hydraulic limitations that fish are able to overcome without become unduly stressed nor fatigued. In doing so, the viability of designing a generic fishway model applicable to all river systems that could cater for freedom of movement of all fish species was also explored. Although the performance of a standard vertical slot channel was successfully improved, upon conclusion of the study it was found that implementing a vertical slot fishway at gradients as steep at 1:5 is not feasible excepting in the case of fishways that are shorter than eight to ten pools long. It is recommended that a minimum gradient of 1:10 be considered for all fishways longer than 10 pools and that resting pools of approximately double the volume of the rest of the pools be incorporated at the turning points of the fishway channel. Further recommendations of design as well as factors to consider when designing an ecologically sound fishway are also provided in the concluding chapter (Chapter 5).

xxiii | P a g e SUMMARY

The provision of fishways is shown to successfully mitigate impacts of fragmentation of aquatic habitat, but is only one factor amongst a multitude of drivers of ecological change to consider when an integrative and holistic conservation plan is considered for the rivers throughout South Africa to preserve the resource.

xxiv | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT

MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH

AFRICA.

CHAPTER 1: Introduction and literature review

1 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

1.1. BACKGROUND & CHAPTER OVERVIEW

The characteristics of fish populations and community structures are determined by the characteristics of the aquatic environment. These fish communities have evolved to adapt to the natural changes that occur within the aquatic environment, but many are dependent on ecosystem characteristics that are not provided for by local site conditions. Many fish species therefore undertake regular and cyclic migrations as part of their life-cycle (Larinier, 2000) to either escape or exploit seasonally-governed variations within an aquatic system. With this knowledge, the maintenance of migratory freedom to the ongoing conservation of fish populations, not only in South Africa but worldwide, has been identified as a leading conservation concern. This has led to an increasing global interest to develop fishways with improved functionality. The degree of functionality is dependent on providing hydraulic parameters that can be successfully overcome by the swimming abilities of the target population of fish species of a specific river system (Bok et al., 2007). An understanding is therefore required of these hydraulic parameters, which fish are capable of negotiating passage through without expenditure of undue energy.

This introductory chapter evaluates the present state of knowledge of fishways and fish migration both globally and in South Africa. To place this thesis in context and provide a focus for review, the chapter starts with an examination of the processes and reasons for migration and the importance of maintaining migratory freedom, the migratory freshwater fish species of South Africa, their distribution and differing migration patterns; and the reasons for decline of these species due to migratory inhibition through river regulating structures. The various types of fishways and their development, both globally and nationally are explored. This is essential to understand the need for well-designed fishways in southern Africa. The chapter concludes with the introduction of the hypothesis and research objectives, followed by an outline of the structure of the remainder of the thesis.

2 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

1.2. FISH MIGRATIONS

Fish are completely dependent on the characteristics of the aquatic environment (Larinier, 2001), which is a dynamic system that is governed by climatic and catchment characteristics. Local conditions may not be suitable to supporting a particular life stage, or not be conducive (often temporarily through seasonal variations) to supporting the immediate physiological requirements of the organisms which inhabit it. The ability to migrate to escape unsuitable local conditions, to locate suitable spawning grounds or to complete a particular life cycle stage therefore becomes essential to the longevity of the organisms (Larinier, 2001). Migratory cycles and patterns are regulated by a complex interplay between environmental cues and controls of physiological functions, as well as genetic differences. Therefore, this process is extremely complex and very important for many fish species (well-known examples being anguillids and salmonids), whose survival and development are highly dependent on its success (Cowx, 1998).

1.2.1. Types of migrations

There are generally two accepted types of migration that are differentiated by distance, namely short to medium migrations and long migrations. Short to medium migrations are undertaken year round where fish remain relatively sedentary, migrating between feeding areas, into floodplains, between various habitat types and to take advantage of varying water temperatures within various areas (Waidbacher & Haidvogl, 1998). These types of regular migratory movements take place both longitudinally and transversely within the system, over varying distances. Long distance migrations are typically associated with seasonal and cyclic spawning migrations, movement out of areas as climatic conditions change seasonally, or feeding migrations that are induced by seasonal changes. These can take place over as much as hundreds of kilometres longitudinally within a system. The distance covered is species-specific and dependent on the climatic zones, characteristics of the watercourse, the natural physical makeup of a system and the presence of artificial barriers (Lucas & Baras, 2001). Each fish species has a particular swimming style and performance. Swimming speeds and endurance levels are directly related to successful capture of prey, evasion of predators and reproduction. These are evolutionary aspects that govern the swimming fitness of fish species (Videler & Wardle, 1991). An understanding of the limitation on the swimming performance and endurance of 3 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW the fish species within a particular reach of a river system is therefore required to provide the correct hydraulic conditions of an ecologically functional fishway design.

An understanding of the types of migrations undertaken within a particular river system as well as the relative spatial context of the river section under consideration are also important in discerning the potential swimming capabilities of the fish species and populations that a fishway should cater for (Zitek, 2006). For example: catadromous fish enter freshwater systems as juveniles with limited swimming and jumping capabilities (Bok et al., 2007). Entering freshwater systems would be their first encounter with unidirectional flow, increased flow velocities and turbulence levels and changes in water levels. The vast majority of coastal rivers, however, has a flat gradient, are slow-flowing and do not include excessive changes in water levels (Davies & Day, 1998). The hydraulic characteristics of a river change toward the headwater reaches of the river, where steep gradients and boulder and bedrock-dominated substrates lead to a variation in water velocities and waterfalls and cascades become increasingly common. Juvenile catadromous fish mature as they migrate progressively upstream and therefore their swimming and jumping capabilities, and therefore their ability to negotiate instream barriers, also increases, thus enabling continued successful upstream passage (Bok et al., 2007). Another important factor to consider is the timing requirements of a fish migration and the hydraulic conditions of the river during that period for example spawning migrations occur in early spring/summer when rivers are subject to flooding events while “recruitment” migrations occur when rivers experience low-flow conditions. The different types of migrations will be outlined within the proceeding sections.

Long distance migrations are separated into categories based on the origin of the migration and the endpoint (Waidbacher & Haidvogl, 1998). There are three categories of migrations, namely potadromous (species that migrate only within freshwater systems, examples of which are all primary freshwater fish), diadromous (fish species that migrate between fresh and salt waters) and oceanodromous (fish species that migrate only within salt waters (oceanic marine species). The latter are not relevant to this study as they are not subject to artificial migratory barriers. There are then various forms of diadromous migrations, namely catadromous (species that reach maturity in freshwater systems and migrate to the sea to breed for example, the anguillid eels; anadromous (species that live

4 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW as older juveniles and sub-adults in the oceans, but upon reaching maturity, migrate inland to freshwater systems to breed for (example the salmonids; and amphidromous (species that migrate freely between fresh and saltwater systems for purposes other than to breed (example: Mugillids (Skelton, 2001).

1.2.2. Reasons for migrations

It has long been known that fish migrate during both regular and cyclic active migrations as well as passive routine migrations (Waidbacher & Haidvogl, 1998). There are many reasons cited for migratory behaviour and patterns in fish, with the main reasons being presented below. Environmental cues are well known to play an important role as a trigger of fish migration (Smith, 1985). Field observations suggested that environmental factors such as a rise in water temperature is a factor determining seasonal or diel (daily) timing for upstream migration (Smith, 1985).

1.2.2.1. Active migrations

The active migrations undertaken on annual or seasonal basis are mostly for breeding and habitat exploitation. En masse feeding migrations are also known to occur, which usually coincide with seasonal changes. Breeding is perhaps the most well-known reason for fish migrations as these migratory patterns are often the most visible due to the large numbers of fish that usually partake in the migration simultaneously (Dingle & Drake, 2007). A number of species of fish have been cited as actively migrating on a seasonal or annual basis for breeding purposes (Skelton, 2001). Perhaps the best known and studied group of species are the salmonids (Gross et al., 1988). These anadromous species reach maturity in the sea and then migrate as sexually mature adults into inland freshwater systems to spawn within mountain streams. These species are regarded as obligatory migratory species and are totally dependent on migratory freedom to complete their life cycle and therefore for long-term survival of the species (Larinier, 2001).

Well known southern African species that undertake seasonal breeding migrations that cover a relatively long distance include species from the families of Cyprinidae and Alestidae (Characins) (Bok et al., 2007, SA Fish migratory database). Active migrations in southern Africa that are also associated with breeding behaviour and completion of life cycle stages include species of Anguillid eels (Anguillidae). Juveniles of these species 5 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW reach maturity within the inland freshwater systems and, upon reaching sexual maturity, migrate downstream toward the ocean to breed (catadromy). Juvenile eels (elvers and glass eels) migrate upstream through coastal rivers during the spring/summer seasons, where they attain sexual maturity within inland water bodies. Upon reaching sexual maturity, they migrate downstream to the oceans to breed (Skelton, 2001).

Active migrations also are undertaken by amphidromous species that seasonally migrate between the marine and estuarine and freshwater habitats in order to breed. These species, for example, from the families Mugilidae (mullets) and Monodactylidae (moonfishes) are able to move freely between the marine and freshwater environments and also undertake cyclic regular migrations between these two habitat types (Skelton, 2001). Active migrations have been observed in the field (Figure 1-1) that occurred within the river system as floodwaters were receding following substantial rainfall within the catchment area within the Sabie River in the Kruger National park (pers. obs. 2004). Large densities of fish were observed attempting to negotiate the weir (a migratory barrier) and other associated infrastructure that created a barrier to upstream migrations. Feeding migrations occur en masse seasonally for example by species of the Clariidae, where large numbers of individuals gather and migrate, usually upstream, within a system. This type of feeding migration can also be viewed as a type of habitat exploitation, where individuals migrate toward an area with a richer source of food, presumably to build up food reserves preceding the breeding season (Skelton, 2001).

Migrations for habitat utilization are common amongst fish species. Suitable hydraulic and chemical conditions of the water, together with climatological events create migratory cues that fish species react to by migrating (usually) upstream. This can be viewed as habitat utilization as many of these individuals are juveniles that are not yet sexually mature.

6 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

1.2.2.2. Passive migrations

The passive migrations are undertaken on a more regular basis and include feeding, local habitat utilization, predator evasion, avoidance of unfavourable local (and often temporary) conditions, and natural nocturnal or diurnal migratory patterns (Dingle & Drake, 2007). These types of migrations are undertaken by more sedentary and habitat specialist species and tend to be over short distances (within the same river reach, or within the same habitat unit within a system). These migrations also are not necessarily limited to longitudinal movements, but include lateral movements of fish as well, such as cyclic infiltration of floodplains and shallow peripheral waters for feeding purposes (Ickes et al., 2005). Species that typify this type of behaviour pattern include, amongst others, species from the families Austroglanidae, Poeciliidae, Amphilliidae and many Cichlidae. Some species that would usually undertake long-distance seasonal migrations also remain within 7 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW the same river sections and migrate locally for habitat exploitation and feeding purposes (Bok et al., 2007, SA Fish migratory database). Accounts of Labeobarbus aeneus (Vaal- Orange smallmouth yellowfish) that passively migrate cyclically throughout the same river segment to exploit habitat features are referred to in O’Brien et al. (2013).

From this it is apparent It is that freedom of movement within an aquatic system is pertinent to the long term survival and overall health of a community of species and that inhibition of this will lead to an overall decline in fish (and certain invertebrate) numbers, diversity and vigour of the overall fish species community due to the lack of genetic diversity.

1.3. BARRIERS TO MIGRATION & IMPLICATIONS OF RIVER FRAGMENTATION

1.3.1. Types of migratory barriers

A migratory barrier refers to any aspect of a watercourse that inhibits the natural freedom of lateral or longitudinal movement of aquatic biota. Natural barriers include large waterfalls, a saline-freshwater barrier such as encountered in estuaries (halocline) or large temperature differences, such as encountered within rivers fed from melting snow within the upper catchment or thermoclines within larger water bodies. These are natural characteristics of watercourses, which have led to natural population isolation and, ultimately, speciation (Welcomme & Cowx, 1998). It is very rarely justified to mitigate for a natural barrier and therefore these barrier types have little relevance to the study.

According to Welcomme & Cowx (1998) and Larinier (2001) unnatural barriers on the other hand may include:

 physical structures (e.g. dams, weirs, causeways, floodgates, etc.);

 hydraulic characteristics (e.g. areas of unnaturally high turbulence such as at a pipeline outfall, or inundated areas with reduced flow);

8 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

 chemical barriers (e.g. point-source pollution outfalls, highly-turbid sections of watercourses within an otherwise unaffected river and artificial haloclines created by point-source pollution);

 thermal barriers (e.g. outlets of water utilised for cooling purposes that unnaturally increases or decrease the water temperature locally);

 behavioural obstructions (e.g. tunnels forcing fish to access unfamiliar depth-flow classes, concrete canals, and other unfamiliar substrates).

As artificial barriers and other river engineering measures are constructed along the major watercourses to aid in commercial development, the decline in fish populations and the consequential loss of the resource became evident (Waidbacher & Haidvogl, 1998; Dugan et al., 2010). This implies that barrier development along watercourses is directly linked to decline in fish populations and diversity.

1.3.2. Implications of barriers on fish migration.

Human activities associated with river channels have interacted with and interrupted the migration of freshwater fish for several millennia. The migration of freshwater fish have been observed and utilised by humanity for thousands of years (Mallen-Cooper, 1996). Indigenous people in the Pacific coastal and interior regions of North America utilize fish resources at river sites where salmon congregated due to hindered movement patterns, or constructed weirs and other devices in rivers to facilitate the capture of migratory species (Jungwirth et al., 1998). The Chinese and Egyptians from two millennia ago created intricate irrigation schemes that required the construction of dams and weirs, all of which must have had profound impacts on migratory fish movements (Northcote, 1998). During the Middle Ages through to the seventeenth century, the abundance of fish within the Danube River was drastically reduced by the construction of strong palisade-like wooden fences that were constructed in a maze-like form that blocked whole sections of the river to intercept the larger migratory species (Waidbacher & Haidvogl, 1998). These structures, known as Huso weirs, and other such structures built over the centuries at various strategic places throughout European rivers have been cited as the reason for the decimation of the migratory sturgeon from the rivers, especially in Budapest. The result is

9 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW that this species has never again occurred in considerable numbers within the middle and upper reaches of the Danube River (Waidbacher & Haidvogl, 1998). Huso weirs largely disappeared from these rivers, although Serbian fishermen utilised one up until World War I (Waidbacher & Haidvogl, 1998). Over the last two centuries, human pressure on aquatic resources has been extremely high, with the greatest impact on fish conservation worldwide coinciding with the onset of the Industrial Revolution (Waidbacher & Haidvogl, 1998). This was when the construction of dams and weirs accelerated to provide readily- available resources (Jackson & Marmulla, 2001). River modification for navigation, hydropower and water regulation has accelerated during this period, with the construction of instream barriers being cited as having the largest impact over all other human activities (Petts, 1984; Lucas & Baras, 2001). Due to this, all of the anadromous and catadromous fish species of certain European countries are considered threatened (Collares-Pereira et al., 2000). Some of these species are considered extinct throughout large areas of central Europe, with others have lost an average of between 50 and 100% of their former range within major river systems (Nicola et al., 1996). Indeed, catadromous and anadromous fish species are under threat worldwide, especially in Europe, due to the pressures of impassable migratory barriers as these species have to migrate between the marine environment and inland freshwater systems in order to survive (Petts, 1984; Nicola et al., 1996; Collares-Pereira et al., 2000). An impassable migratory barrier would inhibit breeding adults from reaching suitable spawning habitat and the loss of the fish resource for the season or eventual decline of the species over the long term (Larinier, 2001).

River modifications have had a distinct impact on fish community structures and continue to do so as they interfere with one or several pertinent fish lifecycle stages. These impacts can be direct (blocking mature fish from reaching spawning grounds) or indirect (such as impacting on other aquatic biota upon which fish depend e.g. food sources) (Lucas & Baras, 2001). These aspects are not unlike those that affect fish conservation throughout rivers of southern Africa, where river regulation through large instream reservoirs, weirs and other instream barriers are commonplace without adequate mitigation measures in place to aid in ecological longitudinal connectivity of the watercourses.

Connectivity of habitats on spatial and temporal scales is viewed as critical to the integrity of aquatic ecosystems and the communities of fishes and other biota (Jungwirth et al.,

10 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

2000). Dams and weirs have drastically modified the landscape, the distribution of physical habitats and their physico-chemical characteristics, including a greater propensity for reduction of flow velocity, warming and de-oxygenation (Davies & Day, 1998). Further physico-chemical alterations of river systems brought about as a consequence of the establishment of regulatory structures include the modification of river substrates through scouring (downstream of the barrier) or siltation (mainly upstream of the barrier) that would impact the overall breeding success of fish (Lucas & Baras, 2001). Alteration of the longitudinal and vertical profiles in river channels has further contributed to the loss of habitat diversity and reduced lateral connectivity in floodplain habitats. Natural flow patterns, which are the major cues for fish undertaking migrations, have been strongly modified in regulated rivers. Dams and weirs have also contributed to reduce the longitudinal connectivity in many rivers – the significance of the impact being related to the height difference in water levels upstream and downstream of the barrier. This not only disrupts upstream spawning migrations but also interferes with compensatory upstream movements (recruitment) after displacement by floods or emigration from habitats that become temporarily unsuitable. Accumulation of migrants below migratory barriers also makes fish more susceptible to exploitation by inland fisheries or predators (Lucas & Baras, 2001).

Based on the reasons and types of migrations undertaken by fish cited above, it is evident that inhibiting the freedom of movement of fish would have negative implications on the fish populations, not only on the short term, but in the long term as well. Various examples and scenarios are outlined below:

Migratory obligates, such as the yellowfish that migrate seasonally for spawning purposes (Skelton, 2001) would, over the short term, suffer a decline in population numbers due to the lowered breeding fecundity and the lack of recruitment by juveniles during the following year. The inability of breeding adults to reach suitable spawning grounds may lead to lowered breeding success of those fish, with the result that there is a reduced number of juveniles within the system and the population will eventually suffer a decline in numbers and a reduction of genetic variation over the long term Dugan et al., 2010). If the impassable barrier is artificial, then an induced speciation may occur, together with lowering of the vigour of the populations. Seasonal migrations are also undertaken to

11 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW avoid adverse local conditions such as avoiding the declining water temperature within temperate climates (Dingle & Drake, 2007). Populations of fish that cannot migrate away from areas that impose seasonally unsuitable conditions may be decimated as climatic conditions tend toward parameters outside of their physiological norms. Habitat exploitation and recruitment into other areas is also important in that the competition for local, and often limited, resources would be reduced by individuals migrating out of the local area. The lack of migration out of an area could also lead to over-population, which, in turn, could lead to increased predation, increased susceptibility to disease and parasite loads, water quality impacts as well as a decline in population vigour.

1.3.3. Fish migratory barriers and the South African perspective

The presence of existing barriers to migration in rivers (weirs, dams, road bridges, causeways, etc.) is considered to be a major factor responsible for the reduction in numbers and range of many migratory fish and invertebrate species throughout South Africa. Impassable artificial barriers to migration are partly responsible for the threatened status of a number of Red Data species in southern Africa (Bok et al., 2004). South Africa is regarded as having a semi-arid climate with an increasing rainfall gradient from west to east (Jury, 2012). Increasing demands on water supply are coupled to the ever-increasing high water demand of mining, agricultural and industrial sectors and the general urbanisation of associated support areas. As a partial means to meet this demand, South Africa is a stakeholder in an international inter-basin transfer scheme, the largest and most noteworthy being the Lesotho Highlands Water Project. This project sees the transfer of water sources within the highlands of Lesotho, through a series of impoundments, to supply the Vaal/Orange River system (the main recipient of the scheme) and then for distribution throughout this catchment and also export into other catchment areas to service the increasing demands on the resource (LHDA, 2013). The recipient systems are highly regulated in order to make the best use, and to calculate and ensure regulated supply, of the water to the end users. This scheme and others like it do indeed meet the supply demand of the water, but has had unfortunate consequences to ecological integrity of the river systems. Regulation of the supply necessitated the establishment of large impoundments, which pose substantial physical migratory barriers to fish and other aquatic biota. Thermo-chemical barriers also occur at the outfall localities of the inter-basin transfers due to discharges of water with different chemical and temperature

12 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW characteristics than that of the receiving system. All of these have had an impact on fish populations and species community structures within the affected regions.

Dams throughout South Africa, such as Hartbeespoort Dam (Figure 1-2), have been constructed to ensure a reliable water supply to the agriculture, commercial, industrial and domestic sectors, as well as for flood attenuation and recreational purposes (Bok, 1990; King et al., 2003). The significance of the impact on fish ecological conservation depends on the locality of the impoundment in relation to the catchment area and what habitat types are being affected. Impoundments are generally constructed within the mature river reaches as this enables efficient capture of the catchment resource. This does mean, however, that major impoundments fragment large portions of the catchment area, with significant impacts imposed on fish populations throughout the country. To date, no large impoundments within South Africa provide for fishways, which has a serious impact to the fish populations throughout the country (Bok, 2007). Very few river systems throughout South Africa remain open and free from migratory barriers (Nel et al., 2011).

Figure 1-2: Hartbeespoort Dam wall on the Crocodile (west) River.

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Further to major impoundments along the larger rivers, perhaps one of the most widespread impacting features affecting migratory freedom and longitudinal connectivity of river systems throughout South Africa are flow-gauging structures. The South African Department of Water and Sanitation (DWS) is mandated to measure flow volumes in major rivers throughout the country in order to ensure that volumes can satisfy the designated ecological reserve, that volumes satisfy licenced water users, and that South Africa fulfils its international obligation to allow designated flow-through volumes into neighbouring countries that also utilise trans-boundary river systems (Wessels & Rooseboom, 2009a; DWA, 2011). There are therefore numerous flow-gauging weirs strategically located along the major river systems throughout the country that have largely fragmented the longitudinal connectivity of the rivers. Although not as substantive as the dam walls of the larger impoundments, the large numbers, coupled to the intermittent spacing of these flow- gauging weirs means that they have a widespread and far-reaching impact on the migratory connectivity of rivers.

The first long-term daily measuring structure was constructed on the Van Stadens River in 1865 by the Port Elizabeth Town Council (Wessels & Rooseboom, 2009b). A further two, one on the Vaal River at Riverton in 1885, and another on the Breede River near Robertson in 1898, were constructed before 1900. Several other structures were constructed during World War 1, mostly within the Cape, Free State and Gauteng (a part of the then Transvaal Province) Provinces. Construction of flow-gauging structures grew rapidly after World War 2 until the 1970s, with up to 880 being in operation in 1975 (Wessels & Rooseboom, 2009b), which had by then imposed fragmentation of the longitudinal connectivity of the vast majority of major river systems throughout South Africa. During the 1990s up to 90 of the existing non-standard or non-compliant structures were decommissioned (Wessels & Rooseboom, 2009b). Many of these decommissioned structures still remain in situ, however, and have not yet been removed. By 2007, 782 flow-gauging structures were actively providing flow-gauging data throughout major river systems of South Africa. This is made up of 55% sharp crest weirs and 35% crump weir crests (Wessels & Rooseboom, 2009b). Examples of flow-gauging structures throughout South Africa are provided in Figure 1-3 to 1-8.

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Figure 1-3: A sharp crest flow-gauging weir on the Vaal River at Vischgat.

Figure 1-4: A crump flow-gauging weir at Sendelingsdrift (Blouputs) on the Orange River.

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Figure 1-5: A flow-gauging weir at Goosebay on the Vaal River.

Figure 1-6: A crump flow-gauging weir on the Sabie River located downstream of the Kruger Gate.

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Figure 1-7: A flow-gauging weir on the Crocodile (west) River at Beestekraal.

The height of a flow-gauging structure is determined by the hydrological regime of the river and the requirements of the flow measurements (Wessels & Rooseboom, 2009b). Many flow-gauging structures are therefore relatively low and tend to drown out under high flow conditions (Wessels & Rooseboom, 2009b), which means that the relatively lower structures that occur on river systems that tend to be subject to routine flooding are considered only partial migratory barriers, as they allow passage of fish under higher flow conditions, such as shown in Figure 1-8.

Other instream structures that impact on the migratory freedom of fish throughout the country include irrigation weirs such as Neusberg Weir (Figure 1-9) and silt trap weirs, poorly-designed low-level crossings and causeways (Figures 1-10 and 1-11), and farm irrigation dams (Figure 1-12).

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Figure 1-8: A flow-gauging weir at Klipplaatdrift on the Vaal River. Under flood conditions such as at the time of taking this photograph, the weir tends to drown out and allows a degree of freedom to negotiate across it by stronger-swimming species.

Figure 1-9: An irrigation diversion weir at Neusberg on the Orange River.

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Figure 1-10: A poorly-designed low-level vehicle crossing on the Jukskei River in Midrand that has created a migratory barrier to fish.

Figure 1-11: An abstraction weir on the Jukskei River in Midrand that incorporates a low-level crossing for vehicles. No provision for fishways was provided and therefore the structure creates a migratory barrier.

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Figure 1-12: A weir constructed on the headwaters of the Crocodile (west) River within the Walter Sisulu National Botanical Gardens as part of historical irrigation schemes for the area which has since been abandoned.

Redundant instream infrastructure also forms a significant portion of the instream barriers along river system throughout South Africa. The example which is presented in Figure 1- 13 shows historical infrastructure that serves no purpose. In a number of rehabilitation projects throughout the country, the focus is on removal of this infrastructure (pers. com. Wessels). The ecological integrity of rivers throughout South Africa is protected by a myriad of progressive environmental legislation. The National Water Act (NWA), Act 36 of 1998, together with the National Environmental Management Act (NEMA), Act 107 of 1998, through the Environmental Impact Assessment (EIA) process is intended to ensure that migratory freedom across a proposed development within a watercourse is provided for. Furthermore, the principles of the NWA endorse Integrated Water Resource Management (IWRM) on a catchment scale (Bok et al., 2007), which includes the maintenance of longitudinal connectivity of the river systems. The most common mitigation measure for this impact is the provision of a fishway. This means that that vast majority of new instream developments make provision for fishways within their design and construction. Many older instream barriers are being retro-fitted with fishway structures, especially DWS gauging weirs.

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Figure 1-13: A low-level causeway at an abandoned trout hatchery located at the headwaters of the Magalies River at Maloney’ Eye.

Although many instream barriers are fitted with fishways as a result of this legislation, the majority still requires the impacts to be mitigated as fishways are only fitted to a very small proportion of barriers throughout the country (Bok et al., 2004). This is because these structures have been in place prior to the promulgation of the present environmental legislation. The relevance of maintaining longitudinal connectivity of the river systems is further reduced by many of these fishways being considered to be non-functional or not functioning optimally due to poor designs, poor maintenance or other factors not taken into consideration during the design phase (Bok et al., 2004). The demands of environmental legislation, together with the ongoing construction of instream barriers typical of a developing country, coupled to the overall threat to fish populations throughout the country, means that the development, design and construction of ecologically sound fishways is becoming a pertinent aspect to the conservation of the ecological integrity of river systems. Monitoring surveys have been undertaken of various fishways throughout South Africa, such as monitoring of the fishway at Xikundu Weir (Fouché & Heath, 2013) and monitoring of the fishway at Neusberg Weir (Benade et al., 1995) in an effort to determine the degree of functionality of these fishways. Determining the degree of

21 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW functionality of these and other fishways would allow for advancements for future fishway designs.

There has been a worldwide increase in interest and research effort over the last 15 to 20 years on promoting free passage of aquatic organisms in rivers, as part of the wider goal to restore and conserve aquatic ecosystems, and South Africa is tending to follow the trend. There is an increased appreciation of the necessity of both adults and juveniles of a variety of species (including aquatic invertebrate species) to undertake longitudinal movements in rivers as part of their life history (Mallen-Cooper, 1996; Kamula, 2001; Larinier, 2001; Bok et al., 2007).

1.4. WHAT ARE FISHWAYS?

Fishways are structures consisting of a series of interconnected pools, a channel fitted with flow-directing baffles, or similar devices that dissipate the energy of artificially-induced high-flowing water (such as that due to falling water over an artificial instream structure) to the point that allows migrating fish to negotiate upstream (and downstream) passage across the artificial instream barrier (Larinier & Marmulla, 2004). Fishways have traditionally consisted of a series of step-like pools that get progressively higher, hence the term “fish ladder” that is also often used (Mallen-Cooper, 1996; Kamula, 2001). This is regarded as a rather outdated term and therefore the term “fishway” now appears to be the more widely used and accepted term in more recent literature. The control of water flow, and the energy dissipation of the flowing water, in fishways is achieved by employing devices, such as baffles, that dissipate the energy of the flowing water and maintain velocities within the biokinetic capabilities of migrating fish. Ever since the inception of the idea of providing fishways, advances have been made in designing more efficient structures and therefore a variety of energy dissipating structures has been designed which give rise to a great diversity of fishway types (Mallen-Cooper, 1996; Kamula, 2001).

1.4.1. Historical overview of the development of the concept of fishways

The importance of providing fish unhindered migratory freedom has been realised over the last century, when studies emerged regarding the declining fish populations throughout the river systems of North America, Europe and Asia (Mallen-Cooper, 1996). These countries have been at the forefront of fish passage research as the importance of these inland 22 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW fisheries was identified early on amongst early settlers as a valuable socio-economical resource. The major focus of fish migrations within these areas has, however, focused on the strong-swimming adult salmonids. Mallen-Cooper (1996) provides an historical overview of fishway research and development throughout the world. A brief outline of pertinent developmental milestones will be presented in the text that follows.

The earliest recorded fishways were constructed in Europe 300 years ago (McLeod & Nemenyi, 1941), with legislation requiring fishways on dams and weirs as early as 1662 in France (de Lachadenede, 1931). These early structures consisted of bundles of branches strategically placed to create steps in steep channels to bypass obstructions. The resulting structure could be considered a crude pool and weir or a pre-barrage design. A version of this design was patented in 1837 by Richard McFarlane of Bathurst, New Brunswick, who designed a fishway to bypass a dam at his water-powered lumber mill. The first scientific publications pertaining to fishways, however, were published in the mid-19th century. In an annotated bibliography Nemenyi (1941) listed 97 references dealing with fishways for the period between 1864 and 1938 (Mallen-Cooper, 1996). It is noted, however, that almost all of these papers provide descriptions of fishways with limited explanations or citations on experimental research.

Among the most influential papers of this period are those of Denil (1909; 1938) where the descriptions of principles and designs of a completely new type of fishway are introduced, the Denil fishway. It was also during this period that the ecological impacts of migratory barriers, specifically dam construction, were initially highlighted, but these concepts were only fully explored decades later (Mallen-Cooper, 1996). It is not surprising that these early citations of fishway designs and the impacts of instream artificial barriers on fish populations focused on the salmon fisheries of the northern temperate zones and therefore only generally targeted this group.

As the concepts of catering for fish migrations and freedom of movement developed, it was Cobb (1928) that recognised the problem of juvenile salmon returning downstream over dams and not just adult fish passing upstream. Buck (1912) and Calderwood (1928) were amongst the first researchers to highlight the need for the design of more ecologically

23 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW sound fishway structures that catered for all migratory species within a river system and not just those commercially-important salmon and herring. Mallen-Cooper (1996) indicates that there are three main themes that emerge within the early scientific writings on fishways, namely (1) the failure of fishways to date, (2) that the fishways targeted salmonids primarily, and (3) the continued dichotomy of these two themes that remains to this day, meaning that many newly-designed fishways are hydraulic parameters specific for salmonid species and therefore still fail to cater for the diversity of fish species inhabiting the system.

A benchmark of fishway implementation was in 1939, with the construction of one of the most extensive fishways of its time (Holmes & Morton, 1939) at Bonneville Dam on the Columbia River, located on the northwest coast of the USA. This project was considered unique as it set the benchmark as the first fishway to be extensively assessed following completion. This marked the start of an era of quantitative research into fishways by both biologists and engineers. This was enhanced by the establishment in 1956 of the Fisheries-Engineering Research Laboratory attached to one of the fishways that allowed for manipulative experiments to be undertaken on migrating fish without the need for capture and handling (Mallen-Cooper, 1996). This benchmark then seemed to establish research into critical analysis on the functionality of fishways and, in 1940, McLeod & Nemenyi (1941) undertook a major study on the critical evaluation of various fishway designs in use at the time.

1.4.2. Types of fishways

Since the inception of the idea of provision of fishways, many ideas have been explored and researched worldwide. All of these types can be considered as derivatives of the standard primary types. Some discrepancy does come about within the literature with regards to the classification of fishway types. The older literature classifies fishway types according to the type of energy dissipating approach, which recognised only three basic types, namely the pool and weir, the Denil and the vertical slot fishway (Katopodis & Rajaratnam, 1983). The vertical slot design has been classified in the past as a pool-type fishway, more specifically, a pool and jet-type design, but as this type is gaining worldwide popularity and becoming the focus of developing improved designs through variations of the original theme, many authors now tend to classify it as an independent design. 24 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

Indeed, according to Clay (1995) and Mallen-Cooper (1996), the classification of fishway types include the pool and weir-type fishways (including the vertical slot design); baffle fishways (including the Denil and Alaskan Steep Pass); natural fishways (including the rock-ramp, and bypass fishways); as well as fishways designed specifically for eels and their elvers. Further to this, there are the so called fish elevator types (including the lock, and trap and transport) that offer an automated system driven by the flowing water that traps (captures) fish that have congregated below a barrier, transports them and releases them above the barrier. Although not technically a type of fishway, this is also regarded as a viable mitigation measure providing a means for fish to cross over instream barriers. This concept ties in with the physical capture of fish downstream of a barrier (netting, etc) and physically transporting them for release upstream of the barrier. This is also regarded as a mitigation measure rather than an actual “fishway” design.

The classification of the various fishways reflects basic differences in hydraulic design and the means used to dissipate energy. The variations therefore provide design refinements in order to address various biological and physical parameters such as target species swimming characteristics, headwater variability, and debris and bedload movement. These design refinements then will enable modification of a specific fishway design to accommodate local conditions. For example, a fishway designed for a river close to the coastal regions would have different hydraulic parameters to consider than one that is designed for inland river sections – even of the same river. This is due to different species compositions of coastal rivers compared to inland rivers. A fishway located close to the coastal regions (especially along the east coast of South Africa) would have to cater for juveniles of the catadromous eels as well as amphidromous estuarine-spawning species that then migrate inland (Skelton, 2001; Bok et al., 2007). These juvenile individuals have a relatively lowered swimming ability, jumping and endurance capacity than adult counterparts. A fishway designed for inland rivers would cater for a greater proportion of fish with a greater swimming ability and endurance capacity. An understanding of the typical hydraulic characteristics of a river reach as well as the fish species composition, age classes and community structures is therefore imperative in designing a functional fishway. It can be accepted, however, that a fishway needs to cater for the weakest- swimming species of the system to be regarded as being ecologically functional (Bok et al., 2007).

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For descriptive purposes, fishways designs have been classified into six major types, namely pool-type fishways (and all variations, including the vertical slot type); baffle fishways (Denil); fish locks, lifts and elevators; natural rock ramp (bypass) fishways; eelways; and, although not technically a fishway design but rather a further means of barrier mitigation, the physical capture, collection and transport upstream across the barrier. The following section summarizes the backgrounds on the basic design considerations and the aspects that are considered limitations to these fishway designs.

1.4.2.1. Pool-type fishways

Pool-type fishways, which are widely-used, are a very old concept and are regarded as the first type of fishway to be developed. The basic principle is that a larger drop in water level created by an artificial barrier is divided into a series of smaller drops through a series of regularly spaced interconnected pools bypassing an obstruction thus forming a series of step-like pools. They are usually built within a defined channel and the pools are separated by weirs (Clay, 1995; Mallen-Cooper, 1996; Kamula, 2001; Larinier, 2001). Fish ascend from pool to pool by jumping or swimming over the weirs, or by passing through the orifices or chutes (Katopodis & Rajaratnam, 1983). The hydraulic mechanism of this fishway type is that water cascades over the weirs or flows through orifices and chutes into the pools, setting up a circulation pattern around an axis perpendicular to the channel walls (Katopodis & Rajaratnam, 1983). Through this mechanism, water energy is dissipated and velocities are controlled. The pools within the fishway have two main functions: to offer lower-turbulence resting areas for fish between the physical exertion of negotiating passage between successive pools, and to ensure that the energy of the plunging water as it flows from pool to pool is dissipated sufficiently and not carried over into the next pool. As with all fishways, the design criteria are based on the swimming capacities and behaviour of the species that the fishway must cater for, the hydraulic characteristics of the river system and the geomorphological features of the river as well as the actual barrier site (Bates, 1992; Larinier, 1992a; Clay, 1995; Larinier, 1998).

Throughout the world there is a large diversity of pool-type fishways, which differ in the dimensions of the pools, the type of interconnection between pools, the differential heads between pools and the flow discharge. Pool length can vary from 0.50 m to more than 10 m, the water depth from 0.50 m to more than 2 m. The discharge can vary from minimal 26 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW flow volumes to several m3/s and the slope from more than 20% to less than 5%, most frequently ranging from 10% to 12% (Bates, 1992; Larinier, 1992a; Clay, 1995; Larinier, 1998). Design criteria include the swimming capabilities and behaviour of the species involved, physical attributes presented at the barrier site, the river hydraulic models and field experience. The drop between pools varies from 0.10 m to more than 0.45 m according to the migratory species, but the most frequently encountered drop is 0.30 m. Pool volume is determined from a maximum energy dissipation in the pools which limits turbulence and aeration, which implies that the greater volume the pool holds at a given discharge, the lower the turbulence level will be. The limitation to pool size is determined by the number of pools that need to be constructed within the limited space provided by the barrier site as well as the height of the barrier. Maximum drops between pools are prescribed for difference fish species and therefore the height difference has to be catered for by the number of pools. This often leads to a compromise of the pool volume. Turbulence levels within the pools are a function of the discharge, which means that a pool and weir type of fishway only functions optimally between a relatively narrow range of discharge volumes unless a discharge control mechanism is put into place. This limits its application on rivers that are subject to strong fluctuations in seasonal flow. The maximum turbulence values commonly used vary from 200 watts/m3 for salmonids to less than 100 watts/m3 for small species and juveniles (Bates, 1992; Larinier, 1992a; Clay, 1995; Larinier, 1998).

Pool and weir fishways – These are made up of a series of pools at progressive heights that are connected by overflowing horizontal weirs (Figure 1-14). The standard pool and weir fishway incorporates a weir that has no further modification, where the water overtops the weir in a uniform fashion. A drawback of this standard design is that it does not operate effectively under low-flow as well as considerably high flow conditions and therefore does not function sufficiently within river systems that are subject to great fluctuations in flow volumes without modification to their design (Mallen-Cooper, 1996; Bok et al., 2007). Weir designs that allowed for concentration of the water flow under low-flow conditions have largely been the focus of the modifications of design. These variations include notched weirs and sloping weirs that promote concentrated flow volume under low flow conditions.

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Figure 1-14: A diagram of pool and weir fishways (taken from Katopodis, 1992).

Sloping weirs designs have been shown to allow for the retention of effective passage at flow rates of as little as 4 ℓ/s (Bok et al., 2004). Further adaptations to the weir design include them being sloped in both the left-right and front-back planes (sloping baffle design) (Figure 1-15).

Figure 1-15: A sloping baffle fishway on the Crocodile River (from Bok et al., 2007).

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The latter design was an attempt at ensuring that no air cavity was created at the downstream edge of the weir under certain flow conditions, thereby allowing the passing of a greater number of smaller individuals (including migrating invertebrates) (Bok et al., 2004). The pool and weir fishway type can therefore be sufficiently modified to allow for fish passage under low flow conditions, which effectively increases the functionality of the fishway by increasing the time period of functionality and also allow for the passage of relatively small species and invertebrates. This is especially true for sloping weirs designs that allow for a variation in water volume and velocities over the weir due to the variations in flow depth. Under high flow conditions these fishways tend to drown out and turbulence levels increase as the flow volume through the channel increases (Bok et al., 2004). As there is no flow through the channel and rather a flow from one pool overtopping into the next, another drawback to this design is that it tends to accumulate sediments within the pools unless an orifice at floor level is provided to flush sediments. A drawback to this design modification is that it limits the functionality of the fishway under the low flow conditions as the orifice prematurely drains the pools and only then becomes functional under relatively higher flows.

The principle limitation of this design is therefore the relatively narrow range of effective operating flow. While both the effective volume and the kinetic energy of the entering flow typically increase along with increased flow rate, the kinetic energy increases more dramatically, reaching a point where the effective volume of the pool will no longer dissipate enough energy to provide effective fish passage conditions (Rajaratnam et al., 1988). Therefore the pool and weir type fishways actually operate effectively under lower to moderate flow rates, but begin to exclude weaker-swimming species under higher flows as the turbulence levels increase within the pools.

Pool and orifice fishway – This is a pool and weir design that, instead of the water overflowing from pool to pool over a weir, the pools are connected by submerged orifices located at the base of the interconnecting weir walls between successive pools Figure 1- 16) (including the ‘Borda mouthpiece’ fishway where the orifice is extended into the upstream pool [Michel & Nadeau, 1966]). This concept has often been integrated into the standard pool and weir types to aid in flushing of sediments through the fishway. Thorcraft 29 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

& Harris (2000) noted that many of the original submerged-orifice fishway designs internationally have failed because they favoured only bottom-swimming fish and were not capable of maintaining designed water velocities because of fluctuating headwater and tail water levels. Locally, the limitations of traditional pool and orifice fishway were noted to have limited functionality and therefore, as far as could be ascertained, no pool and orifice fishways based on the traditional design have been implemented. This is largely due to a large proportion of migrating fish species not being bottom dwellers. This design would therefore require a modification of natural behaviour patterns of fish and would therefore only pass a small proportion of the population.

Figure 1-16: Various views of a notched pool and weir fishway with submerged orifices (three-dimensional modelling developed by Ansara Architects).

Pool and weir fishways have a number of advantages and remain a popular choice of fishway design (largely due to their simplicity in design) where the target fish communities, hydraulic parameters (the traditional design cannot accommodate large fluctuations in flow volumes without considerable control mechanisms) as well as geomorphological characteristics (specifically sediment loads) of a river system can accommodate for it.

Sloping Weir Fishways: Widely-sloping weir designs are a popular choice for coastal fishways where a large wetted surface area gradually transitions to deeper water, with

30 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW associated increase in flow velocity. This allows larger fish as well as for juvenile fish (as small as <20 mm), elvers of various eel species and juvenile invertebrates that utilise the wetted peripheral areas as climbing surfaces (Bok et al., 2004). Travade et al. (1998) noted that experience shows that when pool-type fishways are well designed with respect to the different hydraulic criteria they can allow passage for most species. Although not ideally suited to climbing biota, the provision of a splash zone on these sloped fishways has been noted to improve the passage of macro-crustacea (Fievet, 2000). In these sloping baffle fishways the most significant alteration to the fishway is the weir design, where a thicker weir is in place allowing the water to flow over the crest in an adherent nappe. Furthermore, due to the slope across the channel width, a range of depths is available to the migrating fish allowing them to select their preferred depth and current speed when crossing the weir. This adaptation also allows for fish of different sizes to migrate in the same fishway. It was because of these characteristics that this was one of the designs chosen for testing in the study by Lewis (2006).

Vertical slot fishways - A vertical slot fishway (often referred to as a pool and jet fishway) can be regarded as a pool-type fishway with deep and narrow vertical slot interconnections between the pools equalling the full height of the baffle (Figure 1-17). There are no actual weirs between the pools, even though variations to the design do occur such as where a small sill is placed in this opening. The change in heights of water levels between successive pools within the standard design is actually created through directional flow and the resultant water turbulence and not by the placement of an actual weir. The vertical-slot fishways, maximum velocity occurs as water flows through each slot, with the downstream pool acting to dissipate hydraulic energy as well as providing resting areas for ascending fish. The slope of the channel and the intervals between the slots control the water velocity through each slot, so the fishway can be designed to suit the swimming ability of particular ascending fish (Thorcraft & Harris, 2000). This fishway type can accommodate significant variations in upstream and downstream water levels without the need for regulation sections, making it suited to river systems that are subject to strong seasonal flow fluctuations. One reason for this is based on the hydraulic functioning, where the flow patterns inside the pools and water velocities in the slots are almost independent on the water depth in the fishway (Katopodis & Rajaratnam, 1983). Velocity distribution in the slots is even, and the same velocity prevails from bottom of the slot to the water surface (Katopodis & Rajaratnam, 1983; Kamula, 2001). The vertical slot design 31 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW is typically suited for mitigating barriers of between one and six meters in height (Thorcraft & Harris, 2000).

Figure 1-17: A schematic representation of a vertical slot fishway (not to scale) (three- dimensional modelling developed by Ansara Architects).

South African river systems are typically seasonal and are therefore subject to high fluctuations in water level. This fishway type is rapidly gaining popularity given suitable local conditions and much research has been undertaken to establish the most effective designs, which mostly focus on maximum energy dissipation within the smallest pool dimension. This fishway design does, however, have limitations in that the standard design seemingly does not allow free passage of elvers and invertebrates (crabs and prawns) without a modification of the design. It is also vulnerable to blockages by floating debris, necessitating the fitment of debris deflectors (Bok et al., 2004). This fishway design is the focal point of this thesis and therefore design concepts and principles will be expanded on within subsequent chapters.

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1.4.2.2. Baffle fishways

Baffle fishways differ from pool and weir type fishways in that baffle-types do not incorporate a pool that allows for energy dissipation and resting areas for migrating fish. The baffle-type fishway simulates a rapid system and the fish must negotiate passage without allowance for a rest period. Therefore, these fishway designs are mostly aimed at promoting passage of stronger-swimming species.

Denil fishways - These fishways, developed between 1909 and 1938 by Denil in Belgium, were widely used on European rivers, especially in Belgium, Switzerland and France during the first half of the twentieth century (Denil, 1938) and was specifically designed for Atlantic salmon (Larinier, 2001). This design was later tested in the USA in the 1940s, and more recently in the 1980s in France, Canada and Denmark with the aim of simplifying the shape of the original baffles whilst providing sufficient hydraulic efficiency (Lonnebjerg, 1980; Rajaratnam & Katopodis, 1984; Larinier, 1992b).

Rather than separate pools, the Denil fishway design incorporates a series of closely- spaced ‘U’ – shaped baffles (Mallen-Cooper, 1996) (Figure 1-18). The Denil fishway has been widely used throughout the world and are typically installed with a slope of 17-20 % (gradient of between 1:5.8 and 1:5) and have been employed successfully at slopes up to 25 % (gradient of 1:4) (Kamula & Bärthel, 2000). According to Kamula (2001) the flow in a Denil fishway consists of two interacting parts, namely, of the main stream in the central portion of the channel and of a series of systematic lateral streams, each one corresponding to a side pocket created by baffles. The interaction between the main stream and the lateral ones provides the main mechanism for transferring mass and momentum unsymmetrically to the mid axis, and produces considerable turbulence and energy loss. The water mass on the surface in this fishway type is fast moving and reasonably smooth (Katopodis & Rajaratnam, 1983; Kamula & Bärthel, 2000; Larinier, 2001).

A wide range of flows are possible with a Denil fishway, depending on fishway size, slope and water depth requirements, but some design criteria are applicable. The fishway must 33 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW be carefully engineered to provide the required passage conditions; variations of the forebay water surface elevation must be limited to a range of approximately 1 m; the maximum feasible length of individual fishway segments should be typically no longer than 9 m. Longer runs can be accommodated by installing individual sections of fishway with resting pools between sections where fish can recover before attempting the next climb. Denil fishways typically require a high degree of operational supervision and maintenance as it must be kept completely free of debris to avoid altering the flow characteristics of the baffles, which would affect the hydraulic functioning, and therefore the fishway conditions (Rajaratnam & Katopodis, 1984; Thorcraft & Harris, 2000; Kamula 2001; Larinier, 2001). To date there have been no Denil fishways installed within South African rivers.

Figure 1-18: A schematic representation of a plain Denil fishway. The diagram on the right presents the channel with the side wall removed to allow for a clear view of the shape of the baffles.

1.4.2.3. Fish locks, lifts and elevators

Fish lock – A fish lock operates in a similar way to a navigation lock, with examples being found on many European rivers. Fish are attracted into a chamber at the base of a dam or weir, the chamber fills with water to reach the height of the dam or weir, and then fish swim out of the lock and upstream of the dam or weir (Figure 1-19). Fish locks have proven to be relatively inefficient in passing large numbers of fish, which is largely attributed to the discontinuous nature of operation that does not cater for the high volumes of fish that a

34 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW traditional channel fishway would provide, and many fish locks have been abandoned in favour of channel-type fishways (Mallen-Cooper, 1996; Thorcraft & Harris, 2000; Larinier, 2001). The limitations of efficiency of fish locks can however, be mitigated (Larinier, 2001). No such fish locks have been installed in any South African rivers.

Figure 1-19: A schematic representation of a lock fishway (taken from Thorncraft & Harris, 2000).

Fish lifts and elevators - These differ from fish locks because rather than filling a chamber with water, the chamber collection device is lifted mechanically up to the height of the dam (Figure 1-20). Mechanical fish lifts, are appropriate only for large river systems or barriers where there is a large differential between the upstream and downstream water surfaces (Mallen-Cooper, 1996; Thorcraft & Harris, 2000). The main advantages of fish lifts compared to other types of fishway facilities lie in their cost, which is practically independent of the height of the dam, in their small overall volume, and in their low sensitivity to variations in the upstream water level. They are also considered to be more efficient for some species, such as shad, which have difficulty in using traditional fishways. The main disadvantages lie in the higher cost of operation, and maintenance.

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Furthermore, the efficiency of lifts for small species (e.g. eels) is generally low due to the fact that sufficiently fine screens cannot be used, for operational reasons (Larinier, 2001). No such fish lifts or elevators have been installed in any South African rivers.

Figure 1-20: A schematic representation of trap-and-transport fishway (taken from Thorncraft & Harris, 2000).

1.4.2.4. Natural and rock-ramp fishways

Rock-ramp fishways - They are essentially a ramp of rocks placed immediately below a barrier to create a low slope that simulates a rocky stream bed (Figure 1-21). Rock-ramp fishways were developed as a simple and relatively low-cost adjunct to more-formally engineered fishway designs, particularly for overcoming low barriers and in association with stream erosion-control works (Newbury & Gaboury, 1988; Hader, 1991; Mallen- Cooper, 1996; Harris et al., 1998). More recently they are being trialled in Australia, where they have been built on low slopes of 1:20 (Thorncraft, 1993; Thorncraft & Harris, 1996). Rock-ramp fishways are often the full width of the river, but narrower channels have also been built in similar configurations as pool-type or other fishway designs. These rock-

36 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW ramp fishways have also been built on low slopes, usually greater than 1:20 as their aim is to try and simulate natural stream conditions. Some rock-ramp fishways have been built on very low slopes (1:50 to 1:100) as channels simulating a stream that bypasses an obstruction. They have been called ‘diversion channels’, ‘bypass channels’, and ‘natural fishways’ (Thorncraft & Harris, 1996).

Figure 1-21: A schematic representation of a rock-ramp fishway (taken from Thorncraft & Harris, 2000).

Natural bypass cannel-type fishways - The nature-like bypass channel is a waterway designed for fish passage around a particular obstruction which is very similar to a natural tributary of the river (Figure 1-22. The function of a nature-like bypass channel is, to some degree, also restorative in that it replaces a portion of the flowing water habitat which has been lost due to impoundment (Welcomme & Cowx, 1998; Thorcraft & Harris, 2000; Larinier, 2001). These channels are characterised by a very low gradient, generally 1 to 5% (1:20), even less in lowland rivers. Rather than in distinct and systematically distributed drops as in pool type passes, the energy is dissipated through a series of riffles or cascades positioned more or less regularly as in natural water courses (Gebler, 1998). The main disadvantage of this solution is that it needs considerable space in the vicinity of

37 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW the obstacle and cannot be adapted to significant variation in upstream level without special devices (gates, sluices).

As with any other fishway it is recommended that the fish entrance to the artificial river be located as close to the obstruction as possible. Given the very low gradient, it is sometimes difficult to position the entrance immediately below the obstruction, which means it must be further downstream. This may restrict their efficiency, and consequently make them less useful for large rivers (Larinier, 2001). These bypass channel-type fishways are considered to be efficient in passing high numbers of a diversity of species, however, monitoring is difficult due to the naturally-irregular channel dimensions and varying flow conditions. Turbulence levels and flow velocities are also difficult to calculate with any accuracy due to the lack of formal structures.

Figure 1-22: A schematic representation of a natural flow-like fishway (taken from Thorncraft & Harris, 2000).

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1.4.2.5. Eel fishways (eelways)

These are fishways that are specifically built to accommodate juvenile eels (elvers) migrating upstream. They are usually a pipe or channel which is narrow in cross-section and it is lined with stones or nylon brush (Jens, 1971; de Groot & van Haasteren, 1977; Mitchell, 1986; Mallen-Cooper, 1996; Thorcraft & Harris, 2000; Bok et al., 2004). This roughens the sides of the fishway and slows the velocity of the water, and also provides the eels with a damp, complex surface over which to wriggle.

Further developments have taken place to improve the efficiency and pass rate of eelways. These include “eel tiles” (manufactured by Berry and Escott Engineering Company, Taunton, UK), which is a retro-fitted flat tile-like structure with numerous finger- like protrudences fitted to the lower surface of a fishway that eels would utilise to wriggle through by means of hooking their bodies around these protrudences. Improving the overall efficiency of a standard fishway to better accommodate aquatic macro- invertebrates and eels is also an aim of this Thesis. This theme will therefore be dealt with in more detail in subsequent chapters.

1.4.2.6. Trap and transport fishways

Although not an actual design of a fishway channel, the trap-and-transport fishway can be regarded as another fishway design as it is a mechanism that allows the migrating fish to overcome a barrier. The trap-and-transport type of fishway involves attracting and trapping of the fish that congregate below a barrier by means of a swim-in trap, or merely netted by operators, and then physically transporting them over the barrier. This is often regarded as a transitory mitigation measure prior to the establishment of a permanent fishway (Clay, 1995) and would be implemented typically over peak migratory seasons when spawning migrations compel fish to migrate en masse. Trapping and transportation can also be a more long-term measure in the case of very high dams where the installation of a fishway is not considered feasible, or in the case of a series of very close dams intercepting a reach without valuable habitat for breeding (Clay, 1995).

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The initial trapping is commonly done in a short section of pool-type fishway. The fish are then physically transported by road, rail or aerial car (Travade & Larinier, 1992; Clay, 1995; Larinier, 2001). The efficiency of such a fish facility depends mainly on the behaviour of the fish, the success of the trapping procedures and the transport mechanisms that need to be undertaken quickly and efficiently. Within South African rivers, this type of mitigation measure is more fortuitous than routine. Chance encounters of high densities of fish congregations below barriers often compel survey staff to net and transport across a barrier, but this is not regarded as normal, standard nor routine practice.

1.4.3. Fishways around the world

The development and construction of fishways throughout the world has been driven primarily by the identification of the economic value of harvesting from freshwater fisheries resources and the observations of decline of these resources with the establishment of instream barriers. The Salmon fisheries industry is mostly confined to the northern temperate climates of northern Europe, North America and the Arctic zones, and therefore trends in fishway design are largely similar within these regions. It is only more recently that the acknowledgment of the importance to maintaining migratory freedom to all species within a system has been identified, making for river-specific designs. Only the major countries and regions will be discussed in more detail in the proceeding sections. Detailed country accounts of fishways are provided by Mallen-Cooper (1996) and Larinier (2001).

1.4.3.1. North America, Canada & Alaska

The North American region supports a large number of salmon species, with observations of mass seasonal migrations dating back to explorations during the 1800s undertaken by the explorers, Lewis and Clark (USACE, 1997). The establishment of fisheries along these western rivers saw the reduction of fish stocks to the extent that the US Congress was warned of waning stocks in 1888. During the period 1900 to 1930, pollution and dam construction was cited as a major cause of fish stocks decline and then in 1929, the US Army Corps of Engineers undertook to provide fishways on all dams constructed by them to aid in maintaining fish populations within these river systems (USACE, 1997). These early fishways were therefore primarily focuses on conservation of the salmon stocks. North America also has valuable fisheries based on non-salmonid species which are

40 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW maintained through the use of more recent fishways. These species, along with the salmonids, are diadromous species and hence are found in coastal rivers. The maintenance of these commercial fisheries has led to Canada and the USA probably having more fishways than any other country in the world. This should, however, be taken in context as there are reportedly as many as 76,000 dams in the USA, 2,350 of which include hydroelectric operations. Of these, only 22.5% are provided with fish passage facilities (Larinier, 2001). Most of these fishways are pool-type fishways with lateral notches and orifices, or vertical slot pool fishways where it is necessary to accommodate higher upstream and downstream variations in water levels (Clay, 1995). Upstream passage fish facilities have not been specifically designed for potadromous species, and usage by these species is rather fortuitous than targeted, although a large number of these species are known to make use of the fishways. For smaller facilities, vertical slot fishways are the most frequent type of design, together with pool and weir types (Washburn & Gillis, 1985). The Denil fishway is not widely used along the western coastal rivers, except in Alaska for salmon (Onchorhynchus spp.) (Ziemer, 1962; Clay, 1995). Development of fishways along the east coast occurred relatively later (during the 1960s) after the importance of more holistic targeting of species was noted. Therefore there is a greater variety of fishway designs in use within this region, including fish lifts, pool and weir and stream bypasses.

1.4.3.2. South America

Quirós (1989) listed 46 with another 7 planned or under construction after a review of fishways in South America, with the majority being in Argentina, Brazil, Uruguay and Venezuela. Dam construction is cited as the leading cause for the disappearance of many migratory species from the region (Welcomme, 1985; Northcote, 1998), with hydroelectric schemes contributing a major proportion of the 1,100 impoundments noted by Petrere (1989). The main target groups appear to be economically important characins and siluroid catfish and all of these fishways cater only for adult individuals, which are regarded as being powerful swimmers (Mallen-Cooper, 1996). The existing fishway designs in South America are dominated by pool and weir types, with the occurrence of one fish lock, with the earliest fishway having been constructed in 1911 (Quirós, 1989). It should be noted that salmonids designs were found to be unsuccessful throughout South America, but the pool and weir types, together with a vertical slot (either a standard vertical slot

41 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW design or a combination design) were shown to be effective. Only approximately 50% of the fishways are considered to be effective, however (Mallen-Cooper, 1996).

1.4.3.3. European Union

The European Union (EU) includes the following 28 countries: are: Austria, Belgium, Bulgaria, Croatia, Republic of Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden and the UK (http://www.eucountrylist.com, downloaded on 30/12/2015). European water policy was fundamentally reformed by the Water Framework Directive (WFD) (2000/60/EC). This EU directive was translated into national law in Austria in 2003 with the amendment to the Water Rights Act of 1959 (Federal Law Gazette No. 215/1959 as amended). According to the EU Water Framework Directive, all bodies of water must be protected and enhanced with the aim of achieving “good ecological status” and/or “good ecological potential”. A phased approach to rehabilitation of waterbodies throughout the EU, which includes the enhancement of migratory connectivity of watercourses through either removal of restrictive barriers or through making provision for fishways on these barriers. The completion of these objectives has been targeted for 2027, with technical and financial constraints being cited as the main limiting factors for achieving these objectives sooner (http://ec.europa.eu/environment/water/water-framework/index_en.html, downloaded on 30/12/2015).

Due to the large area and multitude of countries and regions included within the EU, the EU area has been divided into main regions within the sections to follow.

1.4.3.3.1. United Kingdom

In England and Wales, a recent inventory indicates that there are approximately 380 fishways, with more than 100 having been built in a nine year period since 1989 (Cowx, 1998). Fishways in this region are built almost exclusively for Atlantic salmon, sea trout and the European eel (Anguilla anguilla). Ireland, pool and weir fishways have been developed, together with fish locks, with the first fish lock being constructed within the later

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1940s to 1950s. Fishways in Scotland, England and Wales include pool and weir (the most popular design [Beach, 1984]), vertical slot and Denil types (Mallen-Cooper, 1996).

1.4.3.3.2. Western Europe

Norway and Sweden seemingly have a long tradition with fishways, with almost 500 fishways having being built within the last 120 years to date, most being of the pool and weir type (Clay, 1995; Mallen-Cooper, 1996) also indicates more recent constructions of pool and weir fishways and Denil fishway in Sweden. This is also due to the early observations of the effects of migratory barriers on salmon fisheries (together with Atlantic salmon, sea trout and the European eel) and therefore the fishways are primarily aimed at the target species. Observations by Grande (1990; 1995) noted that many Norwegian fishways do not function optimally due to poor maintenance.

Fishway development in Finland has, until recently, not been the focus of management of migratory fish and fisheries, but rather on hatchery development. More recently there has been a growing trend to develop fishways (Laine, 1990; Kamula, 1995). Russia reportedly only has constructed four major fish bypass facilities, one of which is a specific eelway and the remainder being Denil and pool and weir types. The impact of over 1,000 dams with very few fishways, on salmon fisheries was noted in 1980 (Lonnebjerg, 1980). There is a changing trend within Denmark to the point that there were approximately 100 fishways developed within the proceeding 10 years (Lonnebjerg, 1990). Most of these have been Denil fishways with some pool and weir fishways, and some low gradient bypass channels that simulate a natural stream (Mallen-Cooper, 1996).

Regulations in force within Germany, Austria and Switzerland mean that almost every dam is provided with a fishway. Sakowicz & Zarnecki (1954) and Jens (1971) described 29 fishways along the Rhine River its major tributaries, as well as three fishways in the Elbe and Weser rivers, which indicates the importance of fishways in this region. Again, the design of these fishways targeted mainly for Atlantic salmon and eels. The most common fishway used within the region is the natural-like bypass channel (Parasiewicz et al., 1998). However, where land is limited, more conventional pool and weir fishways are used (DVWK, 1996). It was in the 1970s that Jens (1971) highlighted the need for a more

43 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW holistic ecological maintenance approach to fishway design to include a greater diversity of species, which saw a changing trend in the approach to fishway designs. Despite the large numbers of fishways as well as the legislature compelling the provision of fishways at all barriers, the fishways on the Rhine River have not been very successful in passing Atlantic salmon, with both Sakowicz & Zarnecki (1954) and Jens (1971) reporting dramatic declines of salmon in Switzerland and elsewhere along the Rhine due to poorly functioning fishways. From personal observations of photographs and descriptions, the failure of functionality of the natural bypass channels has been most probably due the poor placement of the fishway entrance in relation to the barrier. The fish would be unable to locate the entrance of the fishway.

Fishways in France date back to the 17th century (McLoed and Nemenyi, 1941). Despite this, major declines of migratory fish populations were noted during the latter half of the 19th century, with dam construction without fishways being cited as the leading cause (Larinier, 1990). Legislation passed in France in 1984 required fishways at obstructions and this has led to the construction of nearly 300 fishways, including pool-type fishways, Denil and fish elevators (Travade, 1990). Larinier, (1998) reports that the most widely used fishways in France is the pool-type fishway, with more than 150 such fishways having been installed in France in the last 15 years.

1.4.3.3.3. Spain and Portugal

Portugal promulgated a law in 1962 that required the installation of fishways to maintain migratory freedom, but this was not well enforced until 1990, when a necessity analysis was undertaken for all new weirs and dams, and, if required, they were to be fitted with a fishway. As a result of this, about 50 new fishways were built (Larinier & Marmulla, 2004). The problem of the pre-existing dams remained, however, but there has been a positive change in mind set to the point that maintenance of migratory freedom is now treated as a priority. A project to retrofit and restore functionality to non-functional fishways has been initiated.

Elvira et al. (1998) noted that, to date, there were 115 fishways catalogued in Spain, with about one third having been constructed after 1990. These are mainly located at weirs

44 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW and dams of moderate height, with the pool and weir and vertical slot designs being the most commonly used. Additionally, Denil and other non-standard designs have also been used. Many of the fishways were built in rivers where Atlantic salmon and brown trout were found and therefore design criteria focused mainly on catering for these species.

1.4.3.4. Japan and China

Nakamura & Yotsukura (1987) noted that there are probably about 1,000 fishways installed on Japanese rivers. Sasanabe (1990) indicated the occurrence of almost 1,400, which is an indication that approximately 400 fishways were constructed in a three-year period. Nachi & Nagao (1990) undertook a study within a region of Japan and noted that only 18.3% of weirs and dams were provided with a fishway. This is a seemingly low figure, but by world standards is considered to be relatively high (Mallen-Cooper, 1996). Over 95% of the fishways throughout Japan are based on the conventional pool and weir fishways, the others are vertical slot and Denil type. It was noted by Nakamura et al. (1991) that of the first fishways were not efficient because them being based on European designs and were only able to cater for larger fish. Since 1990, a large effort has been made to improve and adapt fishway designs to cater more for local species. Since then, Nakamura (1993) stated that the improvement of fishways is progressing so rapidly that it is known as a fishway revolution and that a broad range of riverine local species are being targeted. Although fishways (mostly pool and weir types) focused mainly on catering for economically-important species, these fishways were noted to be constructed with low slopes (sometimes as low as 1:30) and are able to cater for juvenile and small species. Because of this, these fishways are also effective in passing the Japanese mitten crab (Eriocheir japonicas) (Sasanabe, 1990), which is a novel concept in fishway designing and planning. Japan is one of the few countries that specifically caters for catadromous eel species that migrate upstream as juveniles with very limited swimming abilities. Therefore, specific eelways are widely utilised throughout Japan (Mallen-Cooper, 1996).

There are approximately 86,000 dams and reservoirs throughout China, with the main form of freshwater fisheries management being stocking from hatcheries to maintain a highly-exploited resource (Wang, 1990; Clay, 1995; Mallen-Cooper, 1996). There has therefore been little need for the development of fishways with the result that only 60 to 80 had been built by 1993 (Nakamura, 1993), with the oldest being built in 1950 (Wang, 45 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW

1990). The main target species are potadromous species, mainly four species of carp, and catadromous species, mainly Japanese eel and most of the fishways are of the pool and weir type (Nakamura, 1993).

1.4.3.5. India and Pakistan

Khan (1940) indicated that 12 fishways were built between 1882 and 1938. These were all pool-type fishways, which were considered to be ineffective due to steep gradients, poor placement of entrances and exits and they only operated over a small range of flows. These were also cited as the reasons behind the failure of the majority of the six further fishways located in Pakistan (Ahmad et al., 1962). These fishways, as was the worldwide trend in fishway design, were also designed to target species of economic importance (Mallen-Cooper, 1996).

1.4.3.6. Australia

The need to provide fishways was recognized early in Australia, with 44 fishways being built in New South Wales between 1913 and 1985 (Thorncraft & Harris, 2000). Unfortunately, the majority of these fishways were poorly built or used an inappropriate design and generally were not maintained. Fishways in the tropics and sub-tropics of Australia are found in rivers of the east coast, in the state of Queensland, where Hajowicz & Kerby (1992) (as cited in Mallen-Cooper, 1996) listed 22 fishways. These were all pool- type fishways with overall weirs or submerged orifices apart from one fish lock built in 1992 (Barry 1990; Beitz, 1992; Hajkowicz & Kerby, 1992). More recently, another fish lock and a pool-type vertical slot fishway have been built in Queensland (Mallen-Cooper, 1996). There has been assessment of only two of these fishways. Kowarsky & Ross (1981) reported that 15 species used one of the pool-type fishways, which was on the Fitzroy River Barrage. Although a range of sizes used the fishways, down to 3 cm long, the authors considered the fishway ineffective as only 2,287 fish were collected in 12 months of periodic sampling, which appears to be small number for the tidal barrier of a river with a catchment of 142,450 km2. In addition only five barramundi, a major target species, used the fishway during the sampling period and high numbers of fish were still reported congregating below the barrage (Mallen-Cooper, 1996). On the Burnett River barrage, in the sub-tropics of Queensland, Russell (1991) reported on another pool and weir fishway

46 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW and found similar results to the Fitzroy River fishway. There were low numbers of fish ascending the fishway with similar species, and in this case no barramundi were recorded in the fishway although they were collected immediately downstream (Mallen-Cooper, 1996).

In the south-east coastal drainage areas of Australia, Harris (1984) noted that there were 29 fishways, 23 of which were ineffective because of inadequate maintenance and inappropriate design characteristics such as poorly-located entrances, failure to operate at low flows, and baffle designs that might not suit the behaviour of native fish. These are shared reasons for failures cited by Bok (1990) described for South African fishways and Jowett (1987) for New Zealand fishways.

Mallen-Cooper (1989) described 22 fishways for the Murray-Darling Basin. Like the coastal fishways these were almost all pool-type fishways and in this case the pools were connected by submerged orifices or vertical slots. Seventeen of the fishways were built on slopes that were steeper than standard salmonid fishways. Steeper fishways were more turbulent and more difficult for fish to negotiate (Mallen-Cooper, 1994a,b). Since the indigenous fish are smaller than salmon and are therefore likely to have poorer swimming abilities (Bainbridge, 1958), the steeper fishways were probably impassable to native fish (Mallen-Cooper, 1989).

Apart from the mainland of eastern Australia, including the temperate and tropical regions, there are few fishways. This partly reflects the concentration of the population in this region and the corresponding development of water resources as the majority of Australian’s population are concentrated within the coastal areas. Other fishways can be found in the island state of Tasmania, south of mainland Australia, where there are at least four fishways built for introduced trout as well as for small indigenous galaxiids and elvers (Beumer, 1984; Harris 1986). There are also a few fishways in the south-west of temperate Australia in the state of Western Australia, and these were also apparently built for introduced trout (Beumer, 1980).

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1.4.3.7. New Zealand

The 1947 fishway regulation gave fisheries authorities the right to require a fishway on any dam or weir built on rivers where trout or salmon did or could exist (Larinier, 2001). But, only from the mid-1980s has fishway provision really been undertaken, with some fishways in New Zealand having been built specifically for native migratory fishes (Jowett, 1987; Mitchell, 1995) instead of focusing on economically-important salmonid species only (Mallen-Cooper, 1996). The first of these was a successful eel fishway on the Patea River (Mitchell, 1986) and since then more eel fishways have been constructed, and experimenting with a number of new fishway designs for small fish has also been undertaken (Mitchell, 1995). These have included variations of rock-ramp fishways (termed ‘boundary layer fish passes’ by Mitchell (1995) using rocks to break up the water flow in shallow fishway channels or on concrete ramps, or through the base of weir gates when they are lifted.

1.4.3.8. Africa

1.4.3.8.1. North and Central Africa

In an account of fishways in the tropical region of Africa (Central to North Africa), Mallen- Cooper (1996) noted only two reports of fishways, wherein Petts (1984) reported on a fishway in the River Niger, at the Markala Barrage, which was intended for indigenous non-salmonid fishes but unfortunately it did not have sufficient capacity for the high numbers of migrating fish that were present in this river system. Bernacsek (1984) reported that there were few fishways in Africa and described only two, which were on the Nile River in Sudan. One was at Sennar Dam but it was destroyed soon after construction, and one was at Gebel Aulia and it was built specifically for the migration of Nile perch (Lates niloticus). The latter fishway was considered ineffective because it had poor access for fish, and fish were unable to overcome it.

1.4.3.8.2. Southern Africa

In the temperate regions of Africa, South Africa has been the most progressive in terms of implementing fishways. In the mid to late 19th century, salmonid species were introduced

48 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW with the European and British immigrants to the local streams of the Cape Province (Western Cape) coastal streams in an effort to establish fisheries within these systems (Skelton, 2001). Natural and artificial barriers at the time were fitted with typical pool and weir fishways of North American and European design to aid in enhancing longitudinal connectivity in an effort to establish viable populations of these species mainly Rainbow trout (Oncorhynchus mykiss) that would possibly mimic the lucrative natural fisheries industry of European and North American systems. It was soon realised, however, that local conditions did not suit the establishment of salmonid fisheries and the efforts were largely abandoned. Fishways within the interior rivers of South Africa remained largely based on these European and North American salmon-type fishways prior to 1990, (Bok, 1990). It is noteworthy to mention that South Africa is 10 to 20 years behind North America, Australia and Europe in current fishway research and monitoring programmes. Bok (1990) noted that only seven fishways existed within South Africa, with a further six planned or under construction by 1990, whilst Holtzhausen (2006) indicated that, to date, 57 fishways had been established and reviewed. By comparison, an official survey carried out in the last century revealed that there were more than one hundred pool and weir type fishways already in existence by the late 1800s in France (Philippe, 1897). What it does, however, indicate is that South Africa is progressing relatively quickly in fishway establishment, with approximately 50 fishways having been established within a 15 year period.

Bok (1990) offers a description of the fishways reported on, which included the fishways constructed on the Silwervis Dam (Shingwedzi River), Pioneer Dam (Letaba River), Engelhardt Dam (Letaba River), Martins Dam (Thaka River), Fort Harden Weir (Great Kei), Abbotsford causeway (Nahoon River), Mark’s Drift Weir (Orange River), Douglas Weir (Orange River), Hermanuskraal diversion weir (Great Fish River), Geelhoutboskloof Weir (Geelhoutbos River), gauging weir (Kouga River), Stellenbosch Weir (Eerste River) and Little Berg diversion weir (Berg River) (Appendix A). The first documented account of a fishway was in the Cape (and most likely in South Africa), which was erected at the Stellenbosch irrigation weir in the Eerste River in 1948 (Harrison, 1951). Harrison (1951) also makes mention of a series of step-pools which had been constructed in the Liesbeek River under the Paradise Road Bridge, Newlands, by the Cape Town City Engineer’s Department during that time. Apart from one completed rock-ramp fishway (on the Sabie River in the Kruger National Park [KNP]), these were all pool-type fishways with overfall

49 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW weirs or submerged orifices connecting the pools (Appendix A). High turbulence levels and too great a drop between successive pools were some of the main reasons for limited functionality in passing indigenous species through a large proportion of the existing pool and weir types, together with poor attraction flows and poor placement of the fishway entrance and exits. High seasonal variation in flow volumes of typical South African river systems also meant that these fishways functioned optimally for a relatively small period of time. Many of the smaller rivers (as well as some of the larger ones) are considered to be non-perennial and therefore there are large variances in flow volumes between the high flow and low flow seasons, which is cited as an additional drawback in South African rivers (Heath et al., 2005). Seemingly, no consideration to the design criteria requirements of local species had been given. Critical evaluation of various fishways, together with following of international trends, led to a change in fishway development and design during the 1990s with an increase in construction of fishways. Rivers within established conservation areas were largely the initial focus (examples being pool and weir fishways in the Kruger National Park, where the construction of pool and weir and pool and slot type fishways dominated fishways (Appendix A). It should be noted that national legislature compelling the provision of migratory freedom when an unnatural barrier across a watercourse is constructed within South Africa was only established in 1998 with the promulgation of the National Water Act (NWA) Act 36 of 1998 and the National Environmental Management Act (NEMA) (Act 107 of 1998). It is only since then that research into fishway designs has gained significant momentum.

Unlike rivers in Europe and North America, many of South Africa’s rivers are seasonal and flows fluctuate depending on the season as well as the dry and wet periods that characterise the climate of the country (Hughes, 2005; Wessels & Rooseboom, 2009a). In addition, initial data from monitoring existing fishways in South Africa show that both juvenile as well as adult fish migrate, with the small fish commonly migrating during low- flow conditions as well as high flow conditions (Skelton, 2001), which means that, depending on the locality of the fishway, functionality over a wide range of hydraulic conditions has to be maintained.

As mentioned, it is only since the 1990s that formal and progressive research has gone into developing fishways for South African conditions that can meet the requirements of

50 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW indigenous species and to suit local environmental conditions. A major research project was initiated in 2000, funded primarily by the Water Research Commission (WRC), which aimed at improving the functionality of fishways throughout South Africa. This was through a collaborative study including fish biologists, hydraulic and design engineers and hydrologists, with a particular focus on designing the fishways in accordance to the requirements of the local fish species whilst not interfering with the design and structural integrity of the instream structures. The research undertaken for this thesis formed part of that project initiative, wherein critical evaluation and reform of fishway designs to make them more efficient and applicable to indigenous species conservation forms the main theme.

1.4.3.8.2.1. Pool and weir-type fishways

The existing pool and weir fishways in South Africa, the degree of functionality and varying degrees of efficiency have been reported. Examples of these fishways can be found at Xikundu Weir (Luvuvhu River) (Fouché & Heath, 2013), Marimane Weir (Nzhelele River), Popalin Weir (Nwanedi River), Rabali Weir (Nzhelele River), Kanniedood Dam (Shingwedzi River) (Meyer, 1974), *Pioneer Dam (Letaba River), Mingerhout Weir (Letaba River), *Black Heron Weir (Letaba River), Engelhardt Dam (Letaba River), Piet Grobler Dam (Timbavati River), Hoxani (Sabie River), Lebombo Weir (Komati River) (Bok et al., 2004), Nhlabane Weir (Nhlabane System) (Mastenbroek, 2003), Mzingazi saltwater barrier (Mzingazi River), Hluleka, Cwebe water supply scheme (Mbanyana River), DWESA water supply scheme (Nqabara River), Haga-Haga Weir (Haga-Haga River), Komatipoort Weir (Inkomati system), Abbotsford causeway (Nahoon River), Mark’s Drift Weir (Orange River), *Bulmers Drift causeway (Swartkops River), Geelhoutboskloof Weir (Geelhoutbos River), private farm weir near Citrusdal (Olifants River), Ebb and Flow weir (Kowie River) (Bok and Cambray, 2003) and Rondevlei spillway (Seekooivlei). The pool and weir fishways at Pioneer Dam, Black Heron weir and Bulmers Drift causeway (marked with [*]) combine both a pool and weir-type fishway together with a partial natural rock ramp fishway.

The Xikundu fishway was completed in 2003 and is a typical pool and weir fishway incorporating a standard horizontal weir with staggered notches (Bok et al., 2004) (Figure 1-23). It is divided into three parts namely, the upper section (10 pools), middle section (4 pools) and lower section (9 pools) that are at right angles to one another. The pools are all

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2.4 m wide, approximately 1.8 m long and are 1.2 m deep. The slope of the fishway is 1:10 (Heath et al., 2005). Where two sections join there are two larger resting pools, measuring 2.6 X 2.35 m, of the same depth.

Figure 1-23: Xikundu Weir fishway (photo courtesy of Dr P. Fouché).

The pools are separated with notched baffles and these notches are at alternate ends of consecutive baffles, which allows for dissipation of the energy and creation of resting areas for the fish where the water velocity is greatly reduced and the energy dissipated. A 100 mm pipe at floor level in the baffle wall forms an orifice through which fish can escape when water ceases to flow through the fishway. The downstream entrance to the fishway is constructed with large boulders to guide the fish into the fishway (Fouché et al., 2005). Extensive monitoring has taken place on the fishway between 2004 and 2006 (Fouché et al., 2005; Heath et al., 2005; Fouché, 2006; Fouché & Heath, 2013). Twenty species of fish were found to locate and enter the fishway, while only a select few species successfully utilized the fishway. Although majority of fish species and sizes were found to use the fishway, the low abundance of fish in the upper section, and the higher abundances present when turbulence was low, suggest/imply that the fishway is used by only a small proportion of the total migratory population and therefore not functioning

52 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW optimally. The fishway was considered to function poorly as fish were only occasionally found to be able to ascend the full length of the fishway when its discharge and turbulences were low (70 watts/m3) (Fouché & Heath, 2013).

The 37 m long Kanniedood Dam fishway (Figure 1-24) on the Shingwedzi River, Kruger National Park was completed in 1992 and was placed at the northern-most end of the spillway. It consists of 23 pools, which are subdivided into an upper (eight pools) and lower (15 pools) section (Olivier, 2003). Each of the upper pool has a flat bottom and is 2 m wide, 2 m long and 1.3 m deep while each of the lower pool measures 2.9 m wide, 1.9 m long and 1.1 m deep. The entrance to the upper pool of the fishway is supplied with a sluice gate that can manipulate low flow discharge volumes in the ladder. During the low flow situation of the river, the flow is directed directly from the fishway into the main stream, thus successfully guiding fish to the lower entrance of the fishway. When medium flows are prevailing and the entire spillway overflows, there is still a good chance that a number of fish sense the flow from the fishway and use the route. Olivier (2003) also tried to minimize the flow from the main pool below the spillway with manmade weirs made out of rocks, therefore, enhancing the migration route of the fishway. During higher floods the entrance to the fishway will be obscured by an array of stronger flowing streams and minimal migration activity will take place. As soon as the flow subsides, the presence of the flow from the fishway will again be noticed. After the December 1992 flood, the riverbed leading to the lower entrance of the fishway was transformed by the deposition of silt. This resulted in a shallow sandy flow from the fishway entrance, making it awkward for migrating fish to cross over. A bulldozer was used to open the route again. Gaps between pools were easily blocked by debris. It is reported to be functioning well during intensive monitoring that took place between 1993 and 1999 with 24 species sampled using the fishway (Olivier, 2003). The submerging of the upper entrance notch may alleviate the debris problem to a certain extent, or by placing a debris reflector at the top entrance. In comparison with the former structures, which were built based on knowledge obtained from elsewhere, the Kanniedood dam fishway was designed using criteria and experience drawn from within the KNP itself. Another example of a notched pool and weir fishway is located on the Komati River, within the town of Komatiepoort (Figure 1-25).

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Figure 1-24: Kanniedood Dam on the Shingwedzi River in the Kruger National Park (left), showing the notched pool and weir fishway located on the left bank (right).

Figure 1-25: A notched pool and weir fishway located on the Komati River in Komatiepoort.

The 6.25 m concrete Nhlabane weir in northern KwaZulu-Natal was constructed in 1976 by Richards Bay Minerals in order to provide a source of freshwater for their dune mining operations. Investigations of fish fauna during the 1990’s (Cyrus & Wepener, 1997; Forbes & Demetriades, 2000) indicated that this lower part of the system constituted to an important nursery area for marine fish species with juveniles wholly or partially dependent on estuarine nursery grounds for the completion of their lifecycle. Among other environmental impacts, the weir and sluices gates have effectively blocked natural migration of at least 18 species of fish and five species of macro-invertebrates between the lake and the estuary (Cyrus, 2001). Especially impacting on the catadromous

54 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW freshwater mullet, Myxus capensis, which, until recently, appeared on the Red Data list, owes a drastic decline in numbers in Eastern Cape rivers mainly to the construction of in- channel barriers such as weirs preventing the migration of juvenile M. capensis to freshwater feeding areas (Bok, 1983). In addition, the weir has reduced the previously available “nursery” area for estuarine biota in the Nhlabane system by about 80% (Begg, 1978).

In 1998, Richards Bay Minerals (RBM) built a 74 m long fishway that linked Lake Nhlabane with the Nhlabane estuary. The Nhlabane fishway is a modified pool and weir fishway with a sloping baffle consisting of 98 pools (500 mm long x 900 mm wide x 450 mm deep) arranged in a folded-staircase type design giving a total length of 47 m. Caters for various depths and flow rates. The first section of the fishway has a slope of 1:12 while the remaining section is set at a slope of 1:10. All pools in the fishway are covered with steel grating to provide migrating biota protection from human and other predators, as well as preventing debris from falling into the pools and obstructing water flow and migration. This fishway is state of the art and has been constructed so as to allow many variables to be altered (such as flow rate and water depth). Modified pool and weir fishway creates flow conditions to accommodate the swimming, as well as climbing and crawling behaviour of migratory fish, eels and macro-invertebrates found in the Nhlabane system, which are expected to use the fishway (Bok, 2000). Monitoring programmes that did take place between 1999 and 2003 on the fishway provided some valuable information with regards to functionality (Bok, 2000; Mastenbroek, 2003; Heath et al., 2005). The fishway allowed for the passage of 22 species of fish (ranging between 10 mm and 310 mm TL) and two macroinvertebrate species between the lake and estuary. The fishway caters mainly for upstream movement of small (<50 mm TL) and juvenile fish species than for adult and larger fish. The optimum flow rate for the fishway is regarded as 20-40 ℓ/s.

1.4.3.8.2.2. Vertical slot fishways in South Africa

Research conducted in Australia determined that the vertical slot fishway design was beneficial to passing a diversity of migrating fish species of tropical and sub-tropical rivers, which have a large seasonal variation in flows (Mallen-Cooper, 1997; Stuart, 1997). The vertical slot design is gaining popularity as an effective means of passing fish across barriers, with the first application based on the vertical slot design being implemented at

55 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW the 8 m high Neusberg Irrigation Weir, constructed by the Department of Water Affairs and Forestry (DWAF) at Kakamas on the Orange River in 1993 (Figure 1-26). Although 10 vertical slot-type fishways are listed in the inventory of fishways in South Africa, this is the only near “standard” [based on the designs outlined in Larinier (2001)] vertical-slot fishway of its kind in South Africa (Heath et al., 2005). It consists of a 2 m wide by 2.5 m deep rectangular channel in which pre-cast concrete baffle walls were provided at 3 m intervals. The fishway channel turns back on itself at the midway point, where a resting pool is provided for the fish.

Figure 1-26: The vertical slot fishway that aids in allowing fish freedom of passage across Neusberg abstraction weir.

Monitoring during 1994 and 1995 of this fishway indicate that the fishway is functioning and that a reasonable passing rate is achieved (Benade et al., 1995). The efficiency of the fishway is, however, reduced through poor maintenance and debris routinely clogs the fishway exit, which greatly reduces the flow of water into the channel. The resultant sub- critical flow renders the fishway non-functional. The fish having difficulty in locating the fishway entrance was reported as a further potential concern. This fishway caters mostly for potadromous cyprinid species including small species such as Barbus trimaculatus (Threespot barb). The Neusberg fishway is the result of the first inter-disciplinary attempt at fishway construction in South Africa. The result is a well-considered and well- constructed fishway which from the monitoring results from 1994 and 1995 appeared to 56 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW meet its major goal i.e. allowing minnows (small fish species) to cross the barrier (Benade et al., 1995). The large size range of fish successfully using the fishway (<50 mm to >500 mm in length) suggests that the vertical slot design is suited for a wide range of indigenous species. Sexually ripe adult fish as well as immature sub-adult fish used the fishway, indicating that possibly both breeding and feeding migrations were involved. No definite environmental cues responsible for stimulating migration could be determined due to time constraints and the lack of data.

Derivatives of the standard vertical slot design have been constructed at various localities within South Africa. Formal monitoring of these fishways is generally, but it is assumed that functionality of these fishways is limited due to poor overall design, poorly-located entrances, or poor attention to hydraulic functionality (pers. obs.) (Figure 1-27).

Figure 1-27: Examples of derivatives of the vertical slot fishway design located on various rivers throughout South Africa: Left – Goosebay Fishway (Vaal River); Right – Fishway at the Lower Sabie Weir

1.4.3.8.2.3. Natural bypass channel

There is only one natural bypass channel formally documented in South Africa. It is located on the Sabie River, downstream of the Lower Sabie Rest Camp in the Kruger National Park. This fishway is a semi-natural bypass channel/rock ramp hybrid type fishway consisting of a series of pools partly constructed of concrete, embedded boulders and the sloping bedrock on the southern bank of the Sabie River that forms the foundation

57 | P a g e CHAPTER 1: INTRODUCTION & LITERATURE REVIEW of the weir and bridge (Figure 1-28). The only section where fish can migrate over the dam wall is at the most southern section of the wall where the rocky foundation extends to the crest of the wall. The rock outcrop has a natural declivity to the north along the wall. The dam wall also supports a road crossing over the river by means of a number of pillars or bridge heads. Functionality of this fishway under low flow conditions is limited to two of the openings below the bridge. Only a portion of the fish populations are able to successfully negotiate the fishway under these conditions due to the fall from the horizontal wall to the rocky foundation or water level being too high for many fish to overcome. During higher flows, four of these openings can be utilised by fish and the part of the fishway that includes this relatively large drop tends to drown out. This fishway has been routinely monitored and has been found to be successful. The biological and physical limitations, however, are that fish have difficulty finding the entrance, predation and blockage of the upper entrance to the fishway are problems that remain a matter of concern (Bok et al., 2007).

Figure 1-28: The natural bypass channel constructed on the Sabie River, downstream of the Lower Sabie Weir.

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1.4.3.8.2.4. Combinations of fishway types

Difficult site conditions (difficult terrain, limited space, or sites deemed ecologically sensitive) or advantageous natural site features often lead to novel and innovative fishway designs to be implemented. A series of pre-barrages and an irregular pool and weir fishway was implemented at the Kruger Gate Weir on the Sabie River after it was identified that former attempts at implementing infrastructure to aid fish in upstream passage across the weir were ineffective (Figure 1-29).

Figure 1-29: An informal pool and weir fishway design constructed on the Sabie River, where a series of larger pools (pre-barrages) were constructed to allow for progressive gain in height to help fish negotiate across the weir.

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Figure 1-30: A diagrammatic plan for the fishway that has since been constructed at Klipplaatdrift on the Vaal River following upgrading of the associated weir (compliments of DWA).

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Designing a fishway to be inaccessible to the public is very often necessary, especially within rural areas. The fishway that was designed for the weir at Klipplaatdrift on the Vaal River was constructed in the centre of the watercourse to stop the public from exploiting the fish resource that could be readily collected from the fishway. This necessitated that an innovative design be developed, which resulted in a fishway resembling a series of stepped pools, or pre-barrages to progressively gain the height needed to get across the barrier (Figure 1-29).

1.5. FRESHWATER FISH OF SOUTHERN AFRICA

There are 280 fish species in 105 genera and 39 families (assessment done in 2001 of all continental waters) that occur in Southern Africa (Skelton, 2001). Approximately 64% (179) of the species are primarily freshwater fishes, mostly cyprinids, characins and catfishes and 22% (61) are secondary freshwater species, mostly topminnows and cichlids. Approximately 34 are peripheral and sporadic marine species that are found in only the lower reaches of rivers and coastal lakes, and comprise about 12% of all species recorded in freshwaters. Of these marine species, 11 (32% or 4% of the total fauna) are peripheral marine species and 23 (66% or 8% of the total fauna) are “stragglers” or sporadic marine species. There are five diadromous species in the region that migrate between the sea and the rivers and back to the sea during the course of their life cycle. These are the four eels (Anguilla species) and the freshwater mullet (M. capensis). There are also 24 alien species (about 9% of the total fauna) in southern African freshwaters (Skelton, 2001) (Table 1-1 and Table 1-2). It must also be remembered that it is not only fish that migrate within river systems. There are nine known species of macro- crustaceans (freshwater prawns and crabs) that are known to migrate between the sea or estuaries and freshwater reaches, mostly for breeding purposes (Bok et al., 2004). Most indigenous fish species in South Africa carry out annual migrations within river systems for a number of reasons such as to optimize feeding, to promote dispersal, avoid unfavourable conditions and to enhance reproductive success (Bok, 1984; Bok, 1990; Cambray, 1990; Bok et al., 2004).

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Table 1-1: The Cape Coastal migratory regions in South Africa according to migratory behaviour and swimming ability of migratory biota present (adapted from Bok et al., 2004).

Migratory - Spatial description Main migratory Species (known at present) region A large variety of climbing species such as numerous macro- South-East and Mozambique to crustaceans and eels (Anguilla spp), as well as many South Coast Palmiet River catadromous and amphidromous fish such as mullet (Mugilidae) and Monodactylidae.

Two catadromous mullet species, Mugil cephalus (Flathead Palmiet River to West Coast mullet) and Liza richardsoni (Southern mullet), no crawling Orange River species present that need to be accommodated

Table 1-2: Inland migratory regions and main migratory groups and species (adapted from Bok et al., 2004).

Migratory - Primary Rivers Main migratory groups Key migratory Species region Labeobarbus aeneus, Main stem and Potadromous species of the Labeobarbus kimberleyensis, Orange-Vaal tributaries of the Vaal – genera Labeobarbus, Labeo Labeo capensis, Labeo region and Orange rivers and Barbus umbratus, Barbus paludinosus and Barbus trimaculatus Anguilla mossambica, various The catadromous eel, Anguilla Upper Limpopo River, Barbus species, Labeobarbus mossambica and various Upper Crocodile River (West), polylepis, Labeobarbus potadromous species, most Limpopo Marico River, Lephalala marequensis, Labeo rosae, importantly from the genera region River, Mokolo River, Labeo ruddi, Labeo Labeobarbus, Labeo and Mogalakwena River cylindricus, Labeo molybdinus Barbus and Mesobola brevianalis Anguilla mossambica, Anguilla marmorata, Anguilla bengalensis labiata, Anguilla The catadromous eel, Anguilla Lower Limpopo River, bicolor bicolor, Hydrocynus family, and the catadromous Lower Luvuvhu River, Letaba, vittatus, Labeobarbus macro crustaceans of the genus Limpopo, Shingwedzi, Olifants, marequensis, various Barbus Macrobrachium. Also various Incomati and Komati River, Crocodile species, Labeobarbus potadromous species, most Pongola (East), Sabie-Sand polylepis, Labeo rosae, Labeo importantly from the genera region River, Pongola River, ruddi, Labeo congoro, Labeo Hydrocynus, Labeobarbus, Usuthu River cylindricus, Labeo molybdinus, Labeo and Barbus Chilologlanis anoterus, Chiloglanis swierstrae, Macrobranchium sp. Anguilla mossambica, A. Mkuze River, Tugela The catadromous eel, Anguilla marmorata, Anguilla Kwa-Zulu River, Umfolozi River, family, and potadromous bengalensis labiata, Anguilla Natal inland Umtamvuna River, species of the genera bicolor bicolor, Labeobarbus region Mzimvubu River Labeobarbus and Labeo natalensis, Labeo rubromaculatus Barbus amatolicus, Barbus andrewi, Barbus erubescens, Cape inland Barbus, Labeo and Barbus serra, Barbus Berg and Olifants Rivers region Pseudobarbus species trevelyani, Labeo seeberi, various Pseudobarbus species, Sandelia bainsii

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1.6. HYPOTHESIS & RESEARCH QUESTIONS

The ability of the selected fish species to successfully bypass or negotiate migratory barriers within a river system will need to be assessed by visual observations in the field as well as prototype fishway design testing within the field at various flow rates and gradients. Laboratory testing will also need to be undertaken to determine the functionality of the prototype models under controlled conditions.

1.6.1. Research question

The main research question of this Thesis and therefore the central theme is:

What are the limits to the migratory potential of the selected fish species in terms of swimming and jumping abilities, and how will this help in determining the hydraulic parameters when designing and constructing a fishway?

A further research question is also included:

Can an individual fishway be sufficiently modified to increase efficiency in passing fish, anguillid eels and aquatic macro-invertebrates that require migratory freedom across instream river barriers, whilst still remaining cost-effective and practical for construction?

1.6.2. Hypotheses

1. More accurate data on the general swimming/jumping abilities of South African fish species can be gained through field and laboratory-based experimentation; 2. Laboratory tests of the vertical slot fishway channel (and design variations) can substantiate the data generated from the field testing of the fishway channel by allowing more time to undergo extensive, repeatable testing under controlled, properly calibrated conditions, yielding the exact hydraulics of a system needed by engineers to construct accurately calibrated and ecologically sound fishways.

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3. The vertical slot type of fishway is more successful at passing a wider diversity of fish species and size classes at a steeper gradient than other traditional fishway designs. 4. A single fishway design can be implemented to function as an ecologically sound bypass facility for fish to overcome artificial barriers within a river system that can cater for an average size class for all the species of fish found within the particular river system.

1.6.4. Specific research objectives

 To establish an artificial fish holding system within the aquarium facility at the University of Johannesburg (UJ), which is capable of environmental condition manipulation, to possibly determine what the environmental cues are that stimulate fish to migrate;  To induce fish to attempt to negotiate the experimental channel on a routine basis, variations of the standard vertical slot fishway design can be tested at various gradients and flow conditions using prototype designs on a scale model within the aquarium. This would allow for the determination of the viability of using a vertical slot fishway at steeper gradients that could possibly be implemented at migratory barrier sites along South African river systems. This will enable an investigation into the swimming capabilities of selected fish species housed within the artificial system. Fishway designs and implementation will then be based on a progressive gain in knowledge of the upstream migratory capabilities of the fish instead of a ‘gut feel’ for the fish;  To determine if the standard vertical slot type fishway provided suitable hydraulic parameters for various South African fish species under different flow conditions using controlled flow conditions within the laboratory;  To test a prototype fishway channel using a mobile model fishway at selected sites in Highveld and Lowveld river systems. This needs to be done as all species may not be kept successfully in the aquarium (especially sensitive species);  To ultimately provide progressive information gained from this study to the knowledge of fish migration potential that will can be used to guide future design, implementation and management of fishways in South African rivers.

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1.6.5. Thesis outline

Chapter 1: Introduction and literature review. General introduction to the background and motivation of the study.

Chapter 2: Laboratory trial testing of the vertical slot fishway using indigenous fish species under steeper gradients.

Chapter 3: Field-based trial testing at two different river systems from two different aquatic ecoregions in order to validate laboratory-based data and to expand on species-specific swimming data.

Chapter 4: Case study & lessons learnt: evaluation of the fishway at the DWS Blouputs/Sendelingsdrift Gauging Weir (D8H017), Orange River, Northern Cape Province. Applies a case studies of fishway designs implemented in South Africa

Chapter 5: Conclusions. The final chapter summarises previous chapters and conclusions of the study are made. Suggestions for future research into fishways are given.

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1.7. REFERENCES

Ahmad, M., Ali, C.M. and Ahmad, S. (1962). Designing of fish ladders. Technical Report No. 362/HYD/1962. West Pakistan Irrigation research Institute, Lahore. p. 26. Bainbridge, R. (1958). The speed of swimming fish as related to size and the frequency and amplitude of the tail beat. Journal of Experimental Biology, 35: 109-133. Barry, W.M. (1990). Fishways for Queensland coastal streams: an urgent review. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. pp. 231-238. Bates, K. (1992). Fishway design guidelines for Pacific salmon. Working Paper 1.6. Washington Department of Fish and Wildlife, Olympia WA, 98501-1091. Beach, M.A. (1984). Fish pass design – criteria for the design and approval of fish passes and other structures to facilitate the passage of migratory fish in rivers. Fisheries Research Technical Report No. 78. Ministry of Agriculture, Fisheries and Food, Lowestoft, England. p. 46. Begg, G.W. (1978). The estuaries of Natal. Natal Town & Regional Planning Report, 41: 1- 657. Beitz, E.N. (1992). Dumbleton Weir Fish Lock. Proceedings of the ANVOLD 1992 Conference on Dams. p. 13. Benade, C., Seaman, M.T. and De Vries, C.P. (1995). Fishways in the Orange River system: Neusberg Weir fishway, Marksdrift Weir fishway & Douglas Weir fishway. In: Bok, A. (ed.). Proceedings of the fishway criteria workshop, D’Nyala Nature Reserve, Northern Province 2-5 May 1995. Water Research Commission and the Department of Water Affairs and Forestry, Pretoria, South Africa. Bernacsek, G.M. (1984). Guidelines for dam design and operation to optimize fish production in impounded river basins. CIFA Technical Paper No. 11. FAO. Rome. p. 98. Beumer, J.P. (1980). Lish ladders – steps in the right direction. Wildlife in Australia 17(2): 38-39. Beumer, J.P. (1984). The Lerderberg River fish-ladder. Aqua (June): 16-17. Bok, A.H. (1983).The demography, breeding biology and management of two mullet species (Pisces: Mugilidae) in the Eastern Cape, South Africa. Unpublished Ph.D. Thesis, Rhodes University, Grahamstown, South Africa. p. 268.

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Larinier, M. (1990). Experience in fish passage in France: fish pass design criteria and downstream migration problems. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. pp. 65-74. Larinier, M. (1992a). Passes à bassins successifs, prébarrages et rivières artificielles. Bulletin Franҫais de Pêche et Pisciculture, 326-327: 45-72. Larinier, M. (1992b). Les passes à ralentisseurs. Bulletin Franҫais de Pêche et Pisciculture, 326-327: 73-94. Larinier, M. (1998). Upstream and downstream fish passage experience in France. Chapter 10. In: Jungwirth M., Schmutz S. and Weiss, S. (eds.). Fish migration and fish bypasses. Fishing News Books, Oxford, UK. pp. 127-145. Larinier, M. (2000). Dams and fish migration. Prepared for Thematic Review II.1: Dams, ecosystem functions and environmental restoration. World Commission on Dams: environmental Issues, Dams and Fish Migration, Final Draft, June 30. Larinier, M. (2001). Environmental issues, dams and fish migration. In: Marmulla, G. (ed.). Dams, fish and fisheries: opportunities, challenges and conflict resolution. FAO Fisheries Technical Paper 419. Fisheries Resources Division, FAO Fisheries Department, Rome. Italy. pp. 45-89. Larinier, M. and Marmulla, G. (2004). Fish passes: types, principles and geographical distribution: an overview. In: Welcomme, R.L. and Petr, T. (eds.). Proceedings of the Second International Symposium on the Management of Large Rivers for Fisheries. Volume 2. Food and Agriculture Organization, Bangkok, Thailand. pp. 183-206. Lewis, H.V. (2006). Evaluation of fishway designs for use at the Ebb and Flow region of rivers in the Eastern Cape, South Africa. Unpublished M.Sc. Thesis. Rhodes University. Grahamstown, South Africa. LHDA (Lesotho Highlands Development Authority). (2013). Lesotho Highlands Water Project, Lesotho Highlands Development Authority, Maseru). Accessed July 2013 at URL: http://www.lhwp.org.ls. Lonnebjerg, N. (1980). Fiskepas af modströmstypen meddelser fra Ferskvands fiskerilab (Denil type fish passes). . Reports from the Fresh Water Fish Laboratories).Danmark Fiskeri–og Havundersogelser, Silkeborg, p. 107. Lonnebjerg, N. (1990). Fishways in Denmark. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. pp. 253-259.

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Lucas, M. C. and Baras, E. (2001). Migration of Freshwater Fishes. Oxford, Blackwell Science. p. 420. Mallen-Cooper, M. (1989). Fish passage in the Murray-Darling Basin. In: Lawrence, B. (ed.). Proceedings of the workshop on native fish management, Canberra 16-17 June 1988. Murray-Darling Basin Commission. Canberra, Australia. pp. 123-135. Mallen-Cooper, M. (1994a). How high can a fish jump? New Scientist, (16 April 1994): 142 (1921): 32-37. Mallen-Cooper, M. (1994b). Swimming abilities of adult golden perch, Macquaria ambigua (Percicthyidae), and adult silver perch, Bidyanus bidyanus (Teraponidae), in an experimental vertical-slot fishway. Australian Journal of Marine and Freshwater Research, 45: 191-198. Mallen-Cooper, M. (1996). Fishways and freshwater fish migration in south-eastern Australia. Unpublished Ph.D. Thesis. Sydney, University of Technology, Australia. p. 377. Mallen-Cooper, M. (1997). Priorities for fishways in semi-arid and tropical streams. In: Berghuis, A.P., Long, P.E. and Stuart, I.G. (eds.). Second National Fishway Technical Workshop Proceedings. Conference and Workshop Series, QC97010 Rock Hampton. pp. 27-34. Mastenbroek, W. (2003). Monitoring studies on the Richards Bay minerals variable passage-depth pool and weir fishway located in the Nhlabane Estuary, KwaZulu- Natal. Unpublished Ph.D. Thesis. University of Durban, Durban, South Africa. McLeod, A.M. and Nemenyi, P. F. (1941). An investigation of fishways. University of Iowa Studies in Engineering Bulletin, 24: 1-72. Meyer, S.R. (1974). Die gebruik van vislere in die bestudering van die migrasie gewoontes van vis in die Transvaalse riviersisteme. Unpublished M.Sc. Dissertation, Rand Afrikaans University, Johannesburg, South Africa. Michel, B. and Nadeau, R. (1966). New type of fishway. Bulletin of the Department of Tourism, Fish and Game, Province of Québec, 7: 38. Mitchell, C.P. (1986). More progress on native fish passes. Freshwater Catch, 30: 19-20. Mitchell, C.P. (1995). Fish passage problems in New Zealand. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’95 in Gifu. Publications Committee of the International Symposium on Fishways ’95: Gifu Japan. pp. 33-41. Nachi, K. and Nagao, M. (1990). The example of crossed river structures in Gifu prefecture. In: Komura, S. (ed.). Proceedings of the International Symposium on

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Technologiae Thesis, Department of Nature Conservation, Technikon Pretoria, South Africa. p. 68. Parasiewicz, P., Eberstaller, J., Weiss, S. and Schmutz, S. (1998). Conceptual guidelines for nature-like bypass channels. Chapter 26. In: Jungwirth M., Schmutz S. and Weiss, S. (eds.). Fish migration and fish bypasses. Fishing News Books, Oxford. pp. 348-362. Petrere, M. (1989). River Fisheries in Brazil: a review. Regulated Rivers: Research and Management, 4: 1-16. Petts, G.E. (1984). Impounded Rivers – Perspectives for Ecological Management. London: John Wiley and Sons. p. 326. Philippe, L. (1897). Rapport sur les échelles à poisons, Ministère de l’Agriculture, Commission des Améliorations Agricoles et Forestières. Quirós, R. (1989). Structures assisting the migration of non-salmonid fish: Latin America. COPESCAL Technical Paper No. 5. FAO Rome. Italy. p. 41. Rajaratnam, N. and Katopodis, C. (1984). Hydraulics of Denil fishways. Journal of Hydraulic Engineering, ASCE 110 (9): 1219-1233. Rajaratnam, N., Katopodis, C. and Mainali, A. (1988). Plunging and streaming flows in pool and weir fishways. Journal of Hydraulic Engineering, ASCE 114: 939-944. Rajaratnam, N., Katopodis, C. and Solanki, S. (1992). New designs for vertical slot fishways. Canadian Journal of Civil Engineering, 19: 402-414. Russell, D.J. (1991). Fish movements through a fishway on a tidal barrage in sub-tropical Queensland. Proceedings of the Royal Society of Queensland, 101: 109-118. Sakowicz, S. and Zarnecki, S. (1954). Pool passes: biological aspects in their construction. Roczniki Nauk Rolniczych (Polish Agricultural Annual) 69( Series D): 5-171. Sasanabe, S. (1990). Fishway of headworks in Japan. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. Skelton, P. (2001). A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa. p 395. Smith, R.J. (1985). The control of fish migration. Springer-Verlag, Berlin. Stuart, I.G. (1997). Assessment of a modified vertical-slot fishway, Fitzroy River, Queensland. Queensland Department of Primary Industries Report. pp. 82. Thorncraft, G.A. (1993). Alternatives to traditional pool-type fishways; navigation locks and rock-ramp fishways. In: Mallen-Cooper, M. (ed.). Proceedings of the Workshop on Fish Passage in Australia. Fisheries Research Institute Cronulla, Australia. p. 15.

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Thorncraft, G.A. and Harris, J.H. (1996). Assessment of rock-ramp fishways. Report for the NSW Environmental Protection Authority. Sydney: NSW Fisheries. Thorcraft, G. and Harris, J.H. (2000). Fish passage and fishways in new south wales: a status report. Technical Report No. 1/2000. Office of Conservation NSW Fisheries. Cooperative Research Centre for Freshwater Ecology, Australia. p. 32. Travade, F. (1990). Monitoring techniques for fish passes recently used in France. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. pp. 119-126. Travade, F. and Larinier, M. (1992). Ecluses et ascenseurs à poisons. Bulleting Franҫais de Pêche et Pisciculture, 326-327: 95-110. Travade, F., Larinier, M., Boyer-Bernard, S. and Dartiguelongue, J. (1998). Performance of four fish pass installations recently built on two rivers in south-west France Chapter 11. In: Jungwirth, M., Schmutz, S. and Weiss, S. (eds.). Fish migration and fish bypasses. Fishing News Books, Oxford. pp. 146-170. USACE (U.S. Army Corps of Engineers). (1997). Annual Fish Passage Report: Columbia and Snake Rivers for Salmon, Steelhead, and Shad. North Pacific Division, U.S. Army Corps of Engineers, Portland, Oregon. Videler, J.J. and Wardle, C.S. (1991). Fish swimming side by side: speed limits and endurance. Reviews in Fish Biology and Fisheries, 1: 23-40. Waidbacher, H.G. and Haidvogl, G. (1998). Fish migration and fish passage facilities in the Danube: past and present. In: Jungwirth, M., Schmutz, S. and Weiss, S. (eds.). Fish migration and fish bypasses. Fishing News Books, Oxford. pp. 146-170. Wang, Y. (1990). Design and applications of fish passage and protection facilities in China. In: Komura, S. (ed.). Proceedings of the International Symposium on Fishways ’90 in Gifu. Publications Committee of the International Symposium on Fishways ’90: Gifu Japan. pp. 53-63. Washburn and Gillis (1985). Upstream fish passage. Canadian Electrical Association Publishers, Montreal. Welcomme, R.L. (1985). River fisheries. FAO Fisheries, Technical Paper No. 262. FAO, Rome, Italy. p. 330. Welcomme, R.L. and Cowx, I.G. (1998). Rehabilitation of rivers for fish. A study undertaken by the European Inland Fisheries Advisory Commission of FAO. Fishing News Books, Blackwell Science Ltd. pp. 98-204.

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Wessels, P. and Rooseboom, A. (2009a). Flow-gauging structures in South African rivers. Part 2: calibration. Water SA, 35(1): 11-19. Wessels, P. and Rooseboom, A. (2009b). Flow-gauging structures in South African rivers. Part 1: an overview. Water SA, 35(1): 1-9. Ziemer, G.L. (1962). Steeppass fishway development. Alaska Department of Fish and Game Informational Leaflet, 12: 9. Zitek, A. (2006). Textual description of the river Kamp case study focusing on basic ecological and socio-economic features for an integrative and sustainable development of the riverine landscape. Deliverable of the NaturNet- REDIME project. Vienna. Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU. 31.

77 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT

MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH

AFRICA.

CHAPTER 2: Laboratory trial testing of the vertical slot fishway using indigenous fish species under steeper gradients

78 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

2.1. INTRODUCTION

The overall economical and practical implications of incorporating a fishway into the design and construction of a particular development that creates a migratory barrier are factors that require consideration. The provision of a fishway at such a development, even though being lawfully required, is still largely viewed as superfluous and a necessary evil by developers (pers. obs.). The owners of the development are therefore more likely to take ownership of the provision and management of a fishway as a mitigation measure to overcome migratory barrier formation, if engineers and fish biologists take a practical and cost effective approach. This implies that, whilst a fishway should retain full ecological functionality, the design should be aimed at being economically viable. Ascertaining the maximum limits of hydraulic characteristics that various fish species can overcome without imposing undue stress and swimming fatigue, and translating these hydraulic parameters into a fishway design, will aid in developing and implementing both practical and ecologically sound fishways.

Fish bypass channels are diversion channels that circumvent an instream barrier, which are popular for allowing fish passage across small barriers. These are a type of fishway that are most often observed along European rivers. A low gradient channel is constructed that incorporates low-level cascades, the design of which, are aimed at not exceeding what would naturally occur within the reach of the river. The length of the channel, which is very often convoluted to allow for extra length, is dependent on the height of the barrier that it is designed to cater for. A fish bypass channel such as this could be considered a generic fishway as it would comfortably cater for all fish species within the particular river reach, and is very often considered as the best-case scenario for mitigating a migratory barrier. The implementation of a bypass channel is dependent on geomorphological features, type of barrier, height of the barrier and seasonal variation of the hydraulics of a river system, and it is most often found that this option is not feasible to implement for practical reasons.

Skelton (2001) noted that the majority of fish species that undergo mass migrations for spawning purposes do so when rivers are swollen following the first rains of the season. It is during these times that the increasingly difficult hydraulic conditions within a river are encountered, which implies that fish have the ability to temporarily negotiate extremes in hydraulic conditions. A fishway could therefore be viewed as a temporary 79 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION extreme in hydraulic conditions and could represent the maximum limitations or hydraulic conditions of the natural river cycles. This perspective could be viable if a fishway was only to cater for adults of species that are regarded as being strong swimmers, and not for juveniles or weaker-swimming species. Juveniles and weaker- swimming species tend to seek shelter under extreme hydraulic conditions (Skelton, 2001) and are therefore not active during these periods. The design of a fishway needs to take these species into consideration and, designing a fishway that provides hydraulic conditions representative of extremes would be considered as being non- functional and have limited ecological value.

Designing a fishway with optimal parameters depends largely on the balanced and successful interaction between hydraulic and biological variables (Silva et al., 2004; Rodríguez et al., 2006; Castro-Santos et al., 2009; Silva et al., 2011; White et al., 2011). A complex interplay of physical characteristics of a river system (hydraulic variables - mostly water velocity and turbulence levels), biological characteristics of the fish (mostly swimming capabilities of the fish, taking both sustained and burst speed swimming endurance into consideration) has led to limitations in design protocols in the past (Castro-Santos et al., 2009; Hatry et al., 2013). Historically, the biological approach to fishway designs has looked at simulating the hydraulic conditions of the river under question where limited biological data were available for a specific target species (Williams et al., 2012). A local example of this are the design criteria suggested for a fishway where Austroglanis sclateri (Rock catfish) was the focal species for a fishway to be developed on the Vaal River at Engelbrechtsdrift. The described approach to develop a fishway to cater for this particular species was to record water velocities and turbulence levels that the fish population would normally be exposed to within its localised habitat. Trying to design a fishway that resulted in hydraulic variables that did not exceed these parameters led to proposals of gradients no steeper than 1:100 (1%), resulting in an uneconomical and therefore non-viable fishway. This ultimately resulted in abandoning the development of the fishway (pers. comm. 1Wessels, 2005). This approach to fishway design was also historically taken internationally, but it was found that this approach was not feasible, mainly due to economic and practical reasons (McLeod & Nemenyi, 1941). The provision of biological parameters gleaned through this type of approach has led to the proposal of

1Dr Pieter Wessels, Civil Engineer. Department of Water Affairs, Pretoria, November 2005.

80 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION many non-feasible fishways that never progressed further than the design and costing phase as this approached focused on fishways of low gradients (e.g. 1:25 to 1:20) and relatively small drops (e.g. no greater than 50 mm) between pools. This equated to fishways that were overly long and excessively expensive to construct and therefore were never considered.

Known extrinsic variables that influence migratory movements include fluctuations in water volume, hydrological cycles, turbulence levels, instream obstacles, water temperature, day length, increases or decreases in flow, food availability, lunar patterns, diel patterns, and rainfall events. Studies have shown that the most influential environmental factors are the long-term influence of season and the short-term influence of daily patterns (Bizzotto et al., 2009). Some intrinsic factors include hormone levels that stimulate fish to undertake spawning migrations and instinctual migrations for dispersal, as well as to exploit resources of other areas (Schwalme et al., 1985). Further to this, there are also variations to the degree of stimulation that a community of fish is subjected to that will influence the intensity of the migratory processes. For example, fish will display a stronger compulsion to migrate, therefore displaying a greater capacity for swimming strengths and speeds, after a larger flooding event relative to migrations undertaken after a smaller freshet within a system. Field experimentation, although a vital part of the proofing phase of fishway designs, has its limitations due to these variables, which include limitations on timing, working in difficult circumstances (e.g. difficult terrain and flooding rivers) and working with unpredictable communities of fish.

2.1.1. Choice of experimental fishway design

The vertical slot type of fishway design was chosen for this study after a review of international trends in implementation of various fishways had shown this design to having gained worldwide popularity within recent years (Katopodis, 1992; Rajaratman et al., 1992; Mallen-Cooper, 1006; Welcomme & Cowx, 1998; Larinier, 2001 and Bok et al., 2007). The vertical slot design is currently regarded as the best type of technical fishway where a fishway is required to cater for a wide diversity of fish species (Bizzotto et al., 2009) and hydraulic parameters. The greatest advantage of the vertical slot design is that it remains effective over a wide range of flow rates. When the flow rate increases (as would be coupled to increased flow rates within the river) the relative change in water levels between the successive pools remains constant. This means

81 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION that the water velocity through the slot also remains relatively constant. The turbulence levels within the pools are not unduly influenced by increased discharge rates as turbulences are effectively dissipated by the subsequent increase in pool volume (Rajaratnam et al., 1986). Flow rates within the rivers throughout South Africa are generally strongly seasonal (Davies & Day, 1998), meaning that the systems are subject to a wide range of flow volumes. The vertical slot design would therefore potentially be ideally suited to flow conditions encountered within these rivers.

The first series of vertical slot fishways were constructed at the Hell’s Gate Dam on the Fraser River in Canada (Rodríguez et al., 2006), and since then a large amount of international literature on design parameters, hydraulic characteristics and optimal parameters has also been generated to the point that an almost internationally- standardised vertical slot design exists today. The vast majority of fishway research is undertaken within the northern hemisphere temperate zones and remains primarily aimed at passing the economically important salmonids fishes (Mallen-Cooper, 1996). Limited data, however, exist for a wide diversity of species. The theoretical ideological perception of this fishway design made the vertical slot fishway type a logical choice for testing under local conditions. South Africa implements fishways primarily as a means to promote ecosystem health and conservation of biodiversity (that supersede economic benefits) and therefore the vertical slot type of fishway was chosen as a primary research focus.

Refinement of the vertical slot design to optimise hydraulic conditions and improve functionality has then since dominated the research undertaken on fishways. Some of the most prominent studies on hydraulic parameters on vertical slots have been undertaken by Rajaratnam et al. (1986); Rajaratnam et al. (1992) and Wu et al. (1999). In these papers the authors performed experimental studies on variations of the vertical slot designs, wherein circulation and turbulence patterns within the pools were traced and where the relationships between discharge and depth at the centre of the pool were also studied. Three vertical slot designs were singled out upon completion of these studies. Two of these designs were chosen for further testing by (Rodríguez et al., 2006). It was found that one design performed well under high flow conditions, whilst still retaining functionality under relatively lower discharge rates when the influence of hydraulic parameters following slight variations in baffle placements was tested under various discharge rates and channel slopes. Typical southern African river systems are characterised by large seasonal variation in flow rates and discharges (Davies & Day, 1998). Retention of functionality under low flows as well as

82 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION relatively high flows was therefore a factor that led to the choice of this design variation as potentially the closest to the ideal for use under local conditions. These designs were tested as an engineering study and optimal designs were generated through theoretical analysis (Rodríguez et al., 2006). Little insight, however, was given into the biological requirements or abilities of various fish species to actually utilise the fishway itself or to test if the theoretical ideals suited the biological requirements.

2.1.2. Hydraulic characteristics and concepts within a vertical slot fishway

This study followed the design specifications given by Larinier et al. (2002) and Rodríguez et al. (2006). The dimensions of which are given in Figure 2-1.

0.85A 1.15A 2.08A A

0.41A

6.63A 1.78A 0.42A

0.41A

8.11A

Figure 2-1: The dimensions of a single pool of the experimental vertical slot fishway channel used in this study (adapted from Larinier et al., 2002). All the dimensions of the fishway are given relative to the slot opening width, identified as “A” in figure and the dimensions of each successive pool are a duplicate of the one that precedes it.

The hydraulic principles of fishways and calculations are commonly based on Froudian Similitude Laws due to the relations between inertia and gravity forces (Calluaud et al., 2012). The reason being, that the hydraulic characteristics of a vertical slot channel is governed by gravity-driven free-flow conditions. These hydraulic principles have been found to reproduce flow dynamics comparably well between model testing and fishway

83 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION prototype testing (Katopodis, 1992) and therefore direct comparisons can be made between the hydraulics of model testing and predictions of hydraulic conditions within full-scale fishways.

Due to fishways being predominantly gravity-driven open channels, the water velocity

(Vs) flowing though the slot openings of the fishway can be calculated using:

Where: Vs: water velocity (m/s) g: acceleration due to gravity (9.81 m/s2); DH: height differences in water level from one pool to the next

A limitation to the vertical slot design, which is a general limitation to fishway designs, is that at very low flows a hydraulic condition known as super-critical flow occurs. This is where water free-flows down a slope with no resistance (Chanson & Murzyn, 2008). The vertical slot fishway channel is designed as a flume with a continuous sloping bottom. No opportunity is created for water to pool under low flow conditions as no bottom sills occur anywhere within the channel. Hydraulic resistance (resistance to inhibit the free flow of the water) is created through the placement of vertical baffles within the channel, which force the water through a type of zig-zag motion, which increases resistance to flow. As the discharge volume increases through the fishway, the hydraulic resistance increases, which is a function of increased turbulence created by the baffles. This allows for the accumulation of pool volume. The orientation of the vertical baffles within the vertical slot fishway forces the flowing water to go around a baffle and be directed through the slot into the next pool. This creates a pooling effect at the bottom of each pool. Where the water flowing under lower flow conditions meets the pooled water at the bottom of each pool, a hydraulic jump is created, which is the rapid transition from a super-critical to sub-critical flow transition zone that is characterised by strong turbulence that leads to air entrainment (Chanson & Murzyn, 2008). These hydraulic conditions are regarded as being difficult for fish to negotiate (Bok et al., 2007). Under these low flow conditions there is a small pooling effect at the bottom of each pool. There is therefore a drop in height (water level) as this water runs into the next pool where no hydraulic resistance is encountered until it reaches the pooled water at the bottom of that pool. As the water changes levels (drops) from one

84 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION pool to the next, critical flow conditions occur. As the flow volume into the fishway increases the turbulence of the water also increases, which increases the hydraulic resistance of the flowing water. This, in turn, enhances the pooling effect of the water and the pool volume increases. The hydraulic jump (the point where the water flowing under super critical hydraulic conditions meets the pooled water) moves up the channel with increased flows until it reaches the slot at the top of the pool. A further increase in flow rate sees the hydraulic jump being drowned out. When the change in water levels

(the water level in the slot preceding a pool (H1) relative to the water entering the pool

[H2]) reaches 67%, then submerged flow conditions are said to occur (i.e. when H2/H1 = 67%) This concept is graphically presented in Figure 2-2.

Hydraulic jump drowns Critical flow as flow increases – submerged flow Super critical

Hydraulic jump H1

Figure 2-2: Flow conditions in a vertical slot fishway (adapted from Bok et al., 2007).

The vertical slot type of fishway channel is therefore thought to require a minimum flow rate to function optimally. Only when the discharge increases to overcome critical flow conditions, and the pool is effectively drowned out, are the hydraulic conditions within the fishway channel regarded as theoretically optimal (Rajaratnam et al., 1992). Up to this point, turbulence levels and water velocities through the slots both increase with an increase in flow. The water velocity through the slot does not increase and the turbulence levels increase at a substantially lower rate when the flow rate increases beyond the volumes required to satisfy submerged flow conditions.

At low flows when the water level in the pool below the intake slot is below the level of the floor in the slot (unsubmerged condition), the flow is controlled by critical flow in the slot. Note that all equations are adapted from Rajaratnam et al. (1992), Clay (1995), Mallen-Cooper (1999), Larinier et al. (2002), and Tarrade et al. (2011).

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Under these flow conditions, the discharge (Q) is calculated using:

Where: Q: discharge (m3/s); b: width of slot (m); g: acceleration due to gravity (9.81 m/s2); H1: head at slot entering pool (m); Cd: discharge coefficient (0.9 in model but depends on shape of slot).

At higher flows when the water level in the pool downstream of the slot is higher than the critical depth in the slot, the discharge (Q) is calculated by:

Where: Q: discharge (m3/s); b: width of slot (m); g: acceleration due to gravity (9.81 m/s2); H1: head at slot of entering pool (m); DH: height differences between the pools (m) Cd: discharge coefficient

Following these known variables within a vertical slot fishway channel, the turbulence levels (Pv) within each pool can be calculated using the following:

Where: 3 Pv: turbulence levels (watts/m ) g: acceleration due to gravity (9.81 m/s2); Q: discharge (m3/s); DH: height differences between the pools (m) Vol: the volume of the pool (m3)

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The inter-relationship between pool volume, discharge, velocity through the slot, height difference between each pool and turbulence levels within each pool can be seen from the above equations. At a given channel gradient, the width of the slot dictates the volume of water entering the pool (discharge), which in turn governs the amount of turbulence within the pool at a given volume. The change in heights of the water level between successive pools is a function of the slope of the channel. As the water velocity through the slot opening (between successive pools) is governed by gravity, the steeper the slope of the channel the higher the drop in water levels between successive pools and therefore the higher the water velocity through the slot opening would be. The steeper the gradient, the less volume of water is allowed to remain within the pools (in the absence of any sills within the slot opening), which means that a higher turbulence level within each pool would be encountered. As the discharge into a pool can be calculated at a given slope with a known width of the slot opening, the turbulence levels within the pool can also be determined, as the exact pool dimensions (and therefore water volume) are also known factors within the fishway. The gradient therefore of the fishway channel at a given discharge rate determines the height difference between each pool, the water velocity within the slot opening and the turbulence levels within the pool.

2.1.3. Biological aspects pertaining to the vertical slot fishway

The swimming speed of fish can be broadly categorised into two types, namely sustained speeds and burst speeds (Schwalme et al., 1985; Videler & Wardle, 1991). Sustained speeds and the limits thereof are those speeds that can be endured using aerobic metabolism within red muscle fibres, given appropriate energy reserves (Videler & Wardle, 1991). This type of swimming effort is typically limited to generating movement through lentic environments, maintaining position in lotic environments, and everyday activities associated with movement such as foraging (Bainbridge, 1958; Bainbridge, 1960; Videler & Wardle, 1991, Northcote, 1998). Burst speeds are those movements that utilise white muscle fibres almost exclusively and require anaerobic metabolism, where the limits on endurance are determined by the efficiency of the conversion of energy from nutrients stored within the muscle fibres and the limitations of time and efficiency of removal of metabolic waste from the muscle fibres (Videler & Wardle, 1991). This type of swimming effort is typically utilised by fish for instances such as predator evasion, capturing of prey and overcoming hydraulic obstacles (isolated areas of high water velocity or turbulence levels). Whereas sustained swimming can be endured for a length of time, burst swimming speeds cannot be

87 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION sustained and are typically short-lived, requiring a significant rest period in order for the muscle fibres to successfully metabolise wastes and to gather and store sufficient nutrients to repeat the efforts (Schwalme et al., 1985; Bermúdez et al., 2010). When encountering a flow-velocity barrier, with a flow velocity that exceeds the maximum sustained swimming speed of a fish, a fish has to utilise burst speeds in overcoming it (Schwalme et al., 1985). This implies that a hydraulic barrier that requires a fish to maintain a burst speed longer than what it can sustain, would effectively be a migratory barrier or block to individuals of that species.

In designing a fishway these aspects need to be taken into consideration and the most successful fishway design would be one that exploits, but remains within the limitations of, the maximum burst speeds, whilst allowing for sufficient resting periods between burst speed efforts (Schwalme et al., 1985). An ecologically sound fishway should therefore be designed to allow for areas where the energy is dissipated (resting areas where open pools larger than preceding pools allow for reduction of turbulence levels) or provide for the creation of counter currents within the fishway pools that allow fish to maintain position with minimal effort until they are sufficiently rested to allow for negotiation through to the next pool. Again, this is specific to the target species, the length of the fishway and the particular choice of fishway design. Discharges through the fishway should also be sufficient to maintain fish-acceptable depths (Bermúdez et al., 2010), which is an aspect that is also species specific. These criteria should all be aimed toward the weakest-swimming species or the species requiring the deepest acceptable water depth within the fish species community structures of a system, or to a particular target species when considering a fishway design (e.g. a particularly threatened species, or species of particular socio-economic value) (Castro-Santos, 2005; Williams et al., 2012). Experimental fishway evaluations that look at maximum flow velocities that can be endured by various species then become imperative to deriving parameters important to ecologically effective fishway designs.

In a study by Bermúdez et al. (2010) set one of the limitations to fishway efficiency is that of maintaining fish-acceptable depths, which is different for morphologically different groups of fish species. Focus was mainly on fusiform (sleek and streamlined with minimal drag), compressiform (laterally flattened), depressiform (flattened, typical of bottom-dwellers ) and anguilliform (eel-like) body structures. Results from these studies indicated that species with compressiform body structures (e.g. Cichlidae species) required a relatively greater water depth for efficient swimming. This means 88 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION that a minimum flow is required for the water level in the fishway to effectively drown the flow in the slot and enable various fish species to pass through the slots into each successive pool (Amado, 2012).

Studies have shown that larger fish, in comparison to smaller fish, can swim at higher burst speeds, have a higher endurance for sustained swimming and do not fatigue as easily as smaller species or juveniles (Bainbridge, 1958; Videler, 1993; Peake, 2004). Fish swimming speed is presented in BL/s (body lengths per second) and it has been shown that smaller species and juveniles require larger frequencies of fin movement to achieve forward movement than larger species and adults for the same displacement measured in body lengths per a set time. This implies that juveniles of a particular species would also therefore have a slower absolute swimming speed (in relative body lengths per second) than their respective adult stages, and would mean that this lowered swimming potential would have to be taken into consideration during the design of fishways aimed at passing juvenile life stages of fish. Videler (1993) also highlighted the effects of water temperature on swimming speeds. It was found that swimming speeds (both sustained speeds and burst speeds) were significantly reduced in cooler water temperatures for tropical and subtropical species. Data from the Videler (1993) study were, however, not consistent from species to species as species from temperate regions (e.g. salmonids) were seemingly unaffected by colder water temperatures, many of which were shown to become more active within the cooler water temperatures. Fish that undertake migrations under natural conditions would not be impacted by this, however, as they are adapted to the natural cyclic temperature fluctuations of a river system brought about by seasonal variation. Where this aspect becomes relevant is where a river is subject to artificial temperature fluctuations. An example of this is the outfall of the Lesotho Highlands Water Project (LHWP), where an inter basin transfer from the Katse Dam transfers a large volume of water via the Ash River. This transfer water is considerably colder that the water of the Ash River, which has impacted the system (Lepono et al., 2000). The vast majority of South African fish species are also subjected to cyclic seasonal water temperature variations that have also been shown to govern their movement patterns (Skelton, 2001). The most noteworthy active migrations that take place for spawning purposes or those undertaken for large-scale exploitation of food resources are undertaken when the water temperature begins to increase at the onset of spring. These movements would be impacted by artificial temperature changes of a system.

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2.1.4. Aims and objectives

Hydraulic characteristics of South African rivers also differ quite substantially to those of European and American systems due to climatic, topographical and geomorphological characteristics (Mallen-Cooper, 1996; Bok et al., 2007). This has led to a distinct difference in fish species diversity and dominance by certain groups. Internationally, fishway designs have also mostly been directed at protecting socio- economically important amphidromous and potamodromous fish as a harvestable resource, leading to fishway designs generally only catering for these fisheries resources (Mallen-Cooper, 1996). Smaller species and those less economically important were therefore traditionally not catered for. This was considered a worldwide trend (Mallen-Cooper, 1996; Larinier et al., 2002), with many of the initial fishways being considered as non-functional to a great many species of fish. The vertical slot design has also had limited exposure under South African conditions and therefore local scientific data are scarce (Bok et al., 2007). Experimentation using the internationally standardised vertical slot design parameters was therefore required to assess the applicability of this design to South African fish species under local conditions and to possibly propose modifications to the design to cater for a wider diversity of fish species and size ranges.

The vertical slot fishway design has gained popularity internationally as a versatile design (Katopodis, 1992; Rajaratnam et al., 1992; Puertas et al., 2012), but has had limited exposure within the South African context (Bok et al., 2007). This chapter aims to test the standard vertical slot type fishway under various hydraulic conditions within the laboratory using indigenous fish species representative of various river systems and climatic zones within South Africa. This is done to extrapolate the applicability of this particular design to use under local conditions, as well as to ascertain whether this design could be utilised at steeper gradients and more difficult hydraulic conditions.

The main objective of this chapter are to determine if the standard vertical slot type fishway provided suitable hydraulic parameters for various South African fish species under different flow conditions using controlled flow conditions within the laboratory. In doing so, it aims to test its viability for use under South African conditions using local fish species of varying size ranges and species diversity as test subjects. Emphasis was to be placed on establishing the viability of implementing the vertical slot design at

90 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION steeper gradients. The outcomes of these experiments would enable the refinement of the design in order to maximise the cost-benefit ratio, whilst still retaining the greatest ecological value of the chosen fishway. Variances to the standard design are also experimented with to assess the responses of the fish to adaptions of the standard design to potentially increase the overall efficiency of the fishway channel for local fish species.

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2.2. MATERIALS & METHODS

2.2.1. Laboratory design

2.2.1.1. Environmentally controlled room

The fish holding system and experimental setup were housed within an environmentally-controlled room in the aquarium research facility at the University of Johannesburg. The lighting system was capable of simulating seasonal photoperiod changes, and, being on three independently timed circuits, was capable of simulating twilight transition periods. The room was also insulated and fully temperature controlled. Therefore reasonable simulations of natural seasonal environmental variables could be controlled, which was thought sufficient to induce fish to utilise the fishway channel through activation of instinctual migratory behaviour to ascertain their swimming potential.

2.2.1.2. Housing system

The experimental system was a simulation of various habitat biotopes (e.g. rapids, riffles, runs, glides, pools and backwaters) as well as water velocity-depth classes found within a river system. The experimental system was able to create fast-shallow, fast-deep and slow-deep velocity-depth classes. It was a bricked structure that was plastered, and waterproofed with fibreglass and a final light brown pigmented waterproofing gel coat. The system could hold approximately 15,000 ℓ of water and was designed to provide the different species of fish with their specific hydraulic and habitat requirements (Figure 2-3). This was achieved by providing an initial relatively narrow channel (providing fast-flowing water at the water outlets) that opened up into a wider main holding system that was fitted with baffles to reduce the turbulence within these areas.

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Figure 2-3: Different hydraulic characteristics of housing system; with areas of high turbulence (top left and right) and quieter areas of low turbulence (bottom left and right).

A water pump (0.75 kW) provided circulation and also serviced the filtration process of the fish housing system (Figure 2-4). This comprised of an initial mechanical stage of a pool sand filter (filled with 80 kg of 0.5 mm silica sand) and a biological stage, consisting of two 25 ℓ filter canisters filled with BioBalls® (Figure 2-5). This biological filtration was sufficient to filter the waste products produced from 120 fish with an average mass of 500 g; each fed an optimum amount (3% of fish body mass per day) of food consisting of 30% protein. The mechanical filter was cleaned by backwashing the system and rinsing of the filters through a change of valve position (Figure 2-6). The BioBalls® used in the biological filter canisters were designed and shaped not to clog with fish solid wastes and to allow for maximum surface area for optimal bacterial growth. Therefore, even if fish solid waste made it through the mechanical filter stage; they can simply pass through the biological canisters to be filtered out when they pass through the mechanical filter again.

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Figure 2-4: Filtration system and water pumps used to enhance water flow through the system.

Figure 2-5: Biological filter canisters with ‘BioBalls®’ filter medium.

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Figure 2-6: Valve position selector for system maintenance.

The water flow through the system was enhanced by the addition of two water pumps (1.5 kW and 2.2 kW) (Figure 2-4). The three pumps had a cumulative pumping potential of approximately 54,000 ℓ/hr (approx. 0.015 m3/s). The outlets from the pumps could either be directed back into the holding system to circulate the water, or they could be directed through a fishway channel that originated from a holding tank. The flow rates were fully controllable by in-line valves (Figure 2-7). The flow rates through the respective channels could be adjusted according to the needs of the experimental design.

Figure 2-7: In-line ball valves that control the direction and volume of water passing either into the system channel or the fishway channel.

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The fishway channel was attached to a 1000 ℓ headway tank at its top end and, following an adjustable gradient, emptied into the channel of the housing system (Figure 2-8). This tank was made from marine plywood that was fitted into a galvanised metal frame. The entire structure was then lined with fibreglass and waterproofed with a brown-pigmented gel coat.

Figure 2-8: Fishway headway tank emptying into the first bucket of the fishway channel.

The height of the top tank for the fishway channel was adjustable, which allowed for adjustment of the gradient of the channel. The first experiments were conducted using a vertical slot fishway channel. The gradient of the fishway channel could be adjusted to suit the experimental design and could be measured in two ways. The one method is by using a builder’s spirit level with reference to a scale drawn on the side of the fishway channel, and the second method being the change in depth of the water from one pool within the channel to the next. The former method has the advantage that water need not be flowing through the channel to determine the gradient, as opposed to the latter method that does require water to be flowing through the channel for the gradient to be determined. The actual velocity and power output of the water flowing through the channel can also be determined by incorporating the discharge flow rate of the water and the change in the depth of water in between consecutive pools within the channel into a mathematical equation.

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2.2.2. Experimental fishway channel specifications and variations

2.2.2.1. Standard vertical slot

The experimental fishway channel was a standard vertical slot type fishway based on the design of Larinier et al. (2002) (Figure 2-1). The experimental channel specifications are presented in Table 2-1. In correspondence with the Department of Water Affairs and Forestry, it was suggested that the experimental protocol be designed to optimise fishway conditions for a slope of 1:5, as a need for fishways at that time was for DWS flow-gauging crump weirs that typically have a back slope gradient of 1:5 (pers. comm. 2Wessels, 2005). Because of this, it was decided to determine if a gradient for a vertical slot fishway of 1:5 was in fact feasible. Experiments exposing fish to steeper gradients of 1:4 and 1:3 were also undertaken. The flow rates of the various pumps were measured by timing how long it takes to fill a set volume. Reported flow rates throughout the experimentation represent the average values taken for five replicates of measurements.

Table 2-1: The dimensions and generalised standard testing variations of the experimental fishway channel.

Aspect Measurements Slot width 0.058 m (± 0.002 m) Individual pool width 0.381 m (± 0.02 m) Individual pool length 0.466 (± 0.04 m) 1:3 Experimental channel gradients 1:4 1:5 Dependent on the gradient: Change in water height between 1:3 = 0.160 m pools 1:4 = 0.120 m 1:5 = 0.100 m Channel length 3.6 m Number of successive pools 7 0.0017 m3/s 0.0050 m3/s Flow rates (discharge) utilised during 0.0067 m3/s experimentation 0.0082 m3/s 0.0149 m3/s

Although the experimental channel was constructed to specifications outlined in Figure 2-1, slot width, pool length and pool width were all physically measured throughout the

2Dr Piet Wessels, Civil Engineer. Hydrological Services, Department of Water Affairs, Pretoria.

97 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION experimental channel, with the average values reported on. A summary of the test conditions and main variables is presented in Table 2-1.

The hydraulic characteristics of the fishway at the different gradients and flow rates were calculated using standard equations outlined in section 2.1.2. The discharge, gradient of the channel and the exact dimensions of the various pools were known variables, so water velocity through the slots and the turbulence levels within the pools (as an average value) could be calculated. Random physical measurements of changes in water levels between successive pools allowed for the theoretical data to be verified. A Microsoft Xcel formula was developed by Dr Jan Rossouw3 and Dr Pieter Wessels4 that allowed for hydraulic calculations to be readily calculated.

2.2.2.1. Experimental fishway variations

Further to those standard testing parameters outlined above, different variations to the prescribed vertical slot design were experimented with. A sill was placed within the base of each slot opening that measured 100 mm in order to create a hybrid between the vertical slot and the pool and weir designs. The experimental set was run again at three different gradients at the five different flow rates. The Microsoft Xcel formula was adapted to allow for accurate hydraulic calculations taking into consideration the placement of the sills. As a further variation to the experimental channel, a pebble substrate (average pebble diameter size of 80 - 100 mm) was then also placed throughout the channel on the bottom of to the fishway. The placement of the pebble substrate added a degree of turbulence into each pool, which was a variable that could not be accommodated. The turbulence level within the pools when using the pebble substrate was therefore not calculated.

2.2.3. Fish species

The initial laboratory experimentation was primarily focused on fish species from the Vaal River system. Not all of the species present within the Vaal system were to be tested, but rather key species from each of the respective groups or families of that particular group of fish. Selected fish species included Labeobarbus aeneus as a representative from the yellowfish group and Labeo capensis (Orange River mudfish)

3 Dr Jan Rossouw, Hydrologist, University of Stellenbosch (retired); 4 Dr Pieter Wessels, Hydrologist, Department of Water Affairs and Sanitation, Pretoria. 98 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION representing the mudfish group. The smaller barbs within the system were represented by Barbus paludinosus (Straightfin barb) and B. anoplus (Chubbyhead barb), with the Cichlidae family were represented by Tilapia sparrmanii (Banded tilapia) and Pseudocrenilabrus philander (Southern mouthbrooder). A further species, namely A. sclateri, was also used for experimental trials (Table 2-2). All of these key species were of various size ranges to be representative of both juvenile and sub-adult to adult age classes. All of these fish were sourced from the Vaal River and its tributaries Wilge River and Suikerbosrand rivers, Gauteng Province.

Table 2-2: Fish species from the Vaal River system used during experimental trials of the vertical slot fishway channel.

Size class Species Common name Body form (mm - SL) Depressiform Austroglanis sclateri (Boulenger, 1901) Rock catfish 70-120 (Siluriform) Barbus anoplus (Weber, 1897) Chubbyhead barb 40-55 Fusiform Barbus paludinosus (Peters, 1852) Straightfin barb 35-55 Fusiform Vaal-Orange smallmouth Labeobarbus aeneus (Burchell, 1822) 70-160 Fusiform yellowfish Labeo capensis (A. Smith, 1841) Orange River mudfish 70-110 Fusiform Pseudocrenilabrus philander (Weber, 1897) Southern mouthbrooder 40-55 Compressiform Tilapia sparrmanii (A. Smith, 1840) Banded tilapia 60-125 Compressiform

The fish groups were chosen as representative of the various body forms. Fusiform body structures are species that are regarded as being stronger swimmers (Labeo spp., Labeobarbus spp. and Barbus spp.) and are species that occupy the lower, middle and upper levels of the water column. Compressed body structure species are regarded as being more sedentary in habit, generally occupying quieter areas (Tilapia spp. and P. philander); whilst depressed body form species (A. sclateri) are regarded as bottom-dwelling species that inhabit the fast-flowing waters of riffles and rapids, where cobbles and boulders offer refuge (Skelton, 2001). This variety of fish groups and body forms was also chosen as they represent groups with varying requirements for water flow-depth classes.

2.2.4. Acclimation of fish

Fish were captured from various sites along the Vaal, Wilge and Suikerbosrand rivers and confined to the holding system. They were allowed time to acclimate to the

99 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION conditions of the holding system for a period of approximately 30 days. During this time they were initially maintained at a photoperiod of 12:12 (light/dark) hours, as this was the recorded photoperiod at the time of collection. During the acclimation period, the light period was gradually increased to be 16:8 (light/dark) at the end of the acclimation period. Only the maintenance pump that serviced the filtration system was run during this time. The system allowed for minimal flow during this maintenance period, with only the pump servicing the filtration system running.

Various environmental and physical characteristics associated with the holding system were manipulated in an effort to determine what environmental cues induced the fish to migrate. These included changes in water temperature, changes of lighting regimes and hydraulic characteristics of the system away from the baseline characteristics of the holding system.

2.2.5. Project plan and experimental design

The primary aim of the laboratory experiments was to test the viability of the use of the vertical slot fishway under local conditions by using indigenous fish species as test subjects at steeper gradients. Various hydraulic parameters were to be induced to ascertain the effects on the limitations of swimming abilities of the test fish.

2.2.5.1. Experimental protocol

2.2.5.1.1. Stimulation phase

The holding system was initially run at a reduced (maintenance/baseline) water volume and water flow (approximately 25% of full capacity) with only the maintenance pump running for filtration purposes. This was done for approximately one week and was regarded as a ‘stimulation phase’ with the objective of optimising energy reserves within the fish to be used when negotiating upstream movements within the fishway channel. It was postulated that fish are induced to migrate at the onset of the summer cycle when rivers are swollen by the first rains of the season (Skelton, 2001) and therefore the water level within the system was increased relatively quickly to its maximum capacity and the water flow was simultaneously increased by turning on the two auxiliary pumps with the objective of simulating flooding conditions within a river. The water temperature was reduced by approximately 2°C by adding relatively colder 100 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION borehole water to the system. This also increased the water volume within the system. All the circulation pumps were turned on simultaneously to allow for maximum turbulence throughout the system. The pumped water was directed through the fishway channel, which was set at the lowest allowable gradient of 1:5. It was postulated that increasing the volume of water, with the simultaneous decrease of water temperature, all coupled to an increase in turbulence, would be sufficient to stimulate the fish to migrate up the fishway channel. This procedure was repeated three times over a three-month period (each time allowing for a period of acclimation) to determine the viability of this approach to get the fish to migrate up the channel. The objective of the stimulation phase was therefore to determine which environmental cues were successful in stimulating the fish to initiate a migratory response. If this procedure was found to not adequately stimulate the fish to located the entrance of the fishway and negotiate upstream passage, then fish were to be confined to the last pool of the fishway under crowded conditions. It was assumed that the fish would negotiate the channel to escape the unfavourable conditions that were thus induced.

2.2.5.1.2. Experimental phase

The experimental protocol could be followed only once the fish were found to be actively and predictably swimming up the fishway channel. It was found that confining the fish to the last pool of the fishway channel under crowded conditions was sufficient in inducing movement them to negotiate the channel. The fish that were successful in negotiating the fishway channel were then caught out of the headway tank of the channel and returned to the holding system. The headway tank would be checked for fish after the system was run at five different flow rates (0.0017 m3/s, 0.0050 m3/s, 0.0067 m3/s, 0.0082 m3/s and 0.0149 m3/s) and at three different gradients (1:3, 1:4 and 1:5) for a set time period of approximately one hour. Following this, the circulation was stopped and fish that were in the channel and within the top holding tank were placed within a holding cage within the holding system so that the same individuals could be utilised for further experiments. The size class and species were noted and recorded. After the experimental phase, all of the fish were released into the holding system to recuperate and the fishway channel was set at a new gradient.

Ten individuals of each fish species were used for each experiment. The same individuals were not continuously used, but periodically replaced by other individuals of the same species and similar body measurements from the holding system in an effort to reduce the effects of fatigue and familiarity of the system. 101 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

2.3. RESULTS & DISCUSSIONS

2.3.1. The stimulation phase

2.3.1.1. Manipulation of temperature to induce migrational behaviour

It was found that the reduction in water temperature had an inhibitory effect on migratory behaviour within the experimental group of fish, which was probably due to a stress response by the fish to the change in environmental conditions. This procedure was repeated three times over a three-month period (each time allowing a period of acclimation) and similar repeated results were gained. This procedure was therefore abandoned as a means to stimulate fish to attempt to swim up the channel.

2.3.1.2. Manipulation of flow and other factors to induce migrational behaviour

It was found that exposing the fish within the holding system to increased water flow was adequate and the most successful means of inducing the instinctual behaviour of swimming against the current (i.e. upstream). Reliability of inducing the fish to swim up the channel increased to a degree by concentrating the fish in a holding area at the entrance of the fishway channel under crowded conditions whilst exposed to the current. This particular experimental setup induced a forced swimming behaviour, with fish responding to escape the unfavourable crowded conditions rather than reacting to favourable environmental cues to induce a migratory response. It was observed that this allowed for the most reliable and repeatable results. Fish therefore moved up the channel as an escape response rather than as a response to environmental cues that would otherwise induce natural urges to migrate upstream. The results gained through laboratory experimentation are therefore regarded as conservative values and not a true reflection of the swimming abilities of the fish species that were utilised during the experimentation procedures. It does, however, provide an indication of abilities that can be meaningfully utilised in establishing baseline data. Fish within natural systems that are subjected to natural environmental cues have a stronger urge to migrate and therefore a superior swimming capacity. They would therefore be able to negotiate greater turbulences, water velocities and greater drops in water height to overcome barriers.

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2.3.3. Experimental hydraulic conditions of fishway channel

Figure 2-9 present the hydraulic variables that occur within the chosen experimental vertical slot type of fishway channel at the given channel gradients of 1:3, 1:4 and 1:5 at varying flow rates of a standard vertical slot fishway channel as per the design detailed by Larinier et al. (2002).

The shaded areas in Figure 2-9 indicate the hydraulic conditions where the discharge rate is not sufficient to support submerged flow conditions. Note that all variables within the figures (Figure 2-9 and Figure 2-10) are read off the primary (left) axis, except for turbulence levels within the pools, which are read off the secondary (right) axis. A vertical slot fishway channel is thought to function optimally when the discharge rate through the channel is sufficient to induce submerged flow conditions (i.e. when H2/H1 = 67%) (Larinier, 2001). From Figure 2-9 it can be seen that at a gradient of 1:3, submerged flow conditions tend to be reached at an approximate discharge rate of 0.0313 m3/s, with the corresponding turbulence levels being approximately 663.2 watts/m3. The drop between successive pools at this gradient is 0.160 m, which remains constant throughout the length of the channel under submerged flow conditions. The velocity of the water as it flows through the slot opening increases with increasing discharge rates until submerged flow conditions are reached, and then remains constant at 1.772 m/s. These values are compared to the hydraulic parameters for the same vertical slot fishway channel at a gradient of 1:4. The same hydraulic parameter interactions and effects on one another are experienced at this gradient as for the gradient of 1:3, excepting that submerged flow occurs at a lower discharge rate. At a gradient of 1:4, submerged flow occurs at a discharge rate of approximately 0.0271 m3/s and the Pv values at this discharge rate measure at approximately 422.6 watts/m3. This shows that a gradient of 1:3 of a channel with the same dimensions requires an increase in discharge volume to maintain submerged flow conditions.

At a gradient of 1:4, the drop between pools is a constant 0.120 m, with a water velocity through the slot opening of 1.534 m/s when submerged flow conditions are reached. At a gradient of 1:5, the same channel requires a discharge volume of approximately 0.0248 m3/s, which has a corresponding turbulence value of 314.4 watts/m3, to satisfy the discharge volume required to induce submerged flow

103 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION conditions. This means that the fishway channel at a gradient of 1:5 can reach optimal conditions at approximately 79% of the discharge rate of a channel set at a gradient of 1:3 (less than half) and 87% of a channel set at 1:4, resulting in 47% and 74% of the turbulence levels, respectively. The drop between pools for the channel set at a gradient of 1:5 is a constant 0.100 m. The same channel at a flatter gradient therefore requires a lower discharge rate than what is required for the same channel at a steeper gradient in order to function optimally (i.e. for the discharge rate to be sufficient to satisfy submerged hydraulic flow conditions).

Therefore the turbulence levels, velocity of the water as it flows through the slots and the drop between pools, all decrease, as the gradient of the fishway channel tends to flatten. The discharge rates required ensuring submerged flow conditions are also reduced with a flatter gradient. A flatter gradient at a given discharge rate allows for the greater pooling potential of the water within each pool and therefore results in a greater water volume. A flatter gradient also reduces the drop between pools and, as the water velocity through the slot is a function of gravity (i.e. the higher the drop, the greater the water velocity) and the turbulence is a function of the velocity of the water entering the pool in relation to the volume of the receiving pool, the overall turbulence levels are lower at a given discharge rate. As the gradient tends to zero in a gravity- governed water system, so will the flow. As turbulence can only be induced by the flow of water, the turbulence levels also then tend towards zero.

2.3.4. Results from experimental procedures

After each experiment ran to completion (time periods indicated under each experimental description) the circulation to the fishway channel was stopped and the fish that reached the top holding tank were measured, identified and returned to the bottom holding enclosure. These fish were allowed a week to recuperate prior to the onset of the next experimental procedure.

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3 3 3 Figure 2-9: Effects on discharge Q (m /s), water velocity Vslot (m/s), pool volume Vol (m ) and turbulence levels Pv (watts/m ) for the standard vertical slot type of fishway at a gradient of 1:3, 1:4 and 1:5 as the water head (flow into the fishway) is increased. The shaded areas indicate the hydraulic conditions before the discharge is sufficient to support submerged flow conditions. The discharge, water velocity and volume variables are given on the primary Y-axis and turbulence values given on the secondary Y-axis.

Figure 2-10: Species success rates (L. aeneus, L. capensis, T. sparrmanii, A. sclateri and B. anoplus) using a standard vertical slot fishway channel at three different gradients at given discharge rates under laboratory conditions. Corresponding turbulence (Pv) values are given on the secondary Y-axis.

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It should be noted that the velocity through the slots remains constant only under submerged flow conditions, where maximum velocity of the water through the slot is reached. Discharge was not always sufficient to induce submerged flow conditions throughout the experimental procedures. Discharge values exceeding 0.0248 m3/s maintain submerged flow for the standard vertical slot channel of the dimensions of the experimental channel at a gradient of 1:5. The relatively small scale of the experimental channel meant that the channel overflowed at higher discharges and therefore the experimental channel could not accommodate the flow rates higher than 0.0149 m3/s. This is due to a further hydraulic phenomenon that occurs within a vertical slot fishway. The hydraulic characteristics within a vertical slot fishway are based on the assumption that each pool receives non-turbulent laminar flow. This, however, is only true for the first pool. Each successive pool is subject to latent turbulence from the previous pool, which continues to accumulate the water flows progressively down the channel. This accumulation of turbulence increases the resistance of the water flow through the channel, effectively backing up the water, which leads to the channel overtopping if the channel is not sufficiently deep. This is what happened with the experimental fishway channel and the reason for not undertaking the experimental procedures at higher flow rates. A double volume pool is normally incorporated into a vertical slot channel at the full scale that has more than seven to nine successive pools to overcome this accumulation of turbulence. This then usually also coincides with a 180º turning point of the channel. A turning point in the channel is most often necessary to allow for freedom of placement of the fishway entrance, so the incorporation of a double volume pool serves a dual purpose. The experimental channel was a straight channel consisting of seven pools together with an entrance pool and an exit pool. Without the allowance of a larger volume pool to dissipate the latent turbulence from the previous series of pools, the pools toward the lower end of the channel tended to overtop at higher discharges.

2.3.4.1. Experiment 1: Standard vertical slot

This experiment utilised the standard vertical slot design presented in Figure 2-1, with the fish species used from Table 2-2. The fishway channel was set at three different gradients (1:3, 1:4 and 1:5) with the results of each set of experiments presented in Table 2-3 to 2-5. The hydraulic conditions of the fishway at the different discharge rates for each gradient are also presented in each table. The results of all three sets of experiments are collectively presented graphically in Figure 2-10.

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Table 2-3: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:3 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 369.30 258.50 623.00 604.10 608.30

Vs (m/s) 0.69 0.98 1.08 1.16 1.41 Species Mean SD Mean SD Mean SD Mean SD Mean SD A. sclateri (n = 10) 0 0 6.67 11.55 0 0 16.67 15.28 11.25 21.00 B. anoplus (n = 10) 0 0 0 0 13.33 23.09 0 0 11.25 12.46 L. aeneus (n = 10) 3.33 5.77 10.00 17.32 30.00 10.00 63.33 5.77 65.00 25.07 L. capensis (n = 10) 26.67 11.55 43.33 20.82 73.33 11.55 80.00 17.32 87.50 16.69 T. sparrmanii (n = 10) 3.33 5.77 0 0 13.33 5.77 26.67 25.17 28.75 19.59

Abbreviations: Q (discharge); Pv (turbulence); Vs (water velocity through the slot)

Table 2-3 shows that only a relatively small proportion of the test population of fish successfully negotiated the fishway at a gradient of 1:3 at discharge values lower than 0.0082 m3/s. Below this discharge value saw the exclusion of A. sclateri and B. anoplus from successfully negotiating the fishway. Once this discharge value was exceeded, the fishway channel saw a larger proportion of successful test fish negotiating the fishway. The erratic results that are indicated within Table 2-3 is an indication of the drawbacks of laboratory testing of fishway channels, which relies on the willingness of fish to seek upstream passage through the channel. Therefore, the hydraulic conditions where no individuals of that species negotiated the channel does not unequivocally exclude that species from being able to successfully negotiate a channel under those hydraulic conditions as fish could not be forced to swim up the channel throughout the experimental procedures of this study. It is assumed, however, that high turbulence levels, coupled to the predominance of super critical flow conditions, and a lack of substantive volume within the pools, were a limiting factor to successful passage of these two fish species, which are regarded as the weaker- swimming species of the test population.

The results where the same channel was set at a gradient of 1:4 are presented in Table 2-4. Again, the results are presented graphically in Figure 2-10. What is indicated by the results in Table 2-4 is that there was an overall improved functionality. In looking at the turbulence values, it can be seen that there was a substantive reduction in overall turbulence experienced within each pool relative to when the channel was set at a gradient of 1:3. Again, overall functionality was shown to improve

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at discharge values greater than 0.0067 m3/s. This is again attributed to the predominance of super critical flow conditions throughout the channel.

Table 2-4: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:4 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 207.80 395.00 388.00 390.10 418.80

Vs (m/s) 0.69 0.98 1.08 1.16 1.40 Species Mean SD Mean SD Mean SD Mean SD Mean SD

A. sclateri (n = 10) 6.67 11.55 33.33 15.28 46.67 20.82 63.33 25.17 73.75 19.96 B. anoplus (n = 10) 10.00 10.00 13.33 15.28 53.33 11.55 43.33 15.28 47.50 24.35 L. aeneus (n = 10) 6.67 11.55 30.00 10.00 70.00 10.00 63.33 25.17 73.75 27.74 L. capensis (n = 10) 20.00 0 30.00 20.00 66.67 11.55 83.33 5.77 66.25 29.73 T. sparrmanii (n = 10) 13.33 5.77 20.00 10.00 63.33 20.82 70.00 10.00 76.25 26.69

Abbreviations: Q (discharge); Pv (turbulence); Vs (velocity)

The results where the same channel was set at a gradient of 1:5 are presented in Table 2-5, with the results being presented graphically in Figure 2-10. These results show a progressive improvement of successful passage of individuals of the test population, again showing greater improvement at discharge values greater than 0.0067 m3/s.

What is therefore apparent is the increased success rates of all of the five fish species used for the experimentation when the discharge rate is increased from 5.0 x 10-3 m3/s to 6.7 x 10-3 m3/s for all three channel gradients. The channel tends toward reaching submerged flow conditions at 2.69 x 10-3 m3/s (for a gradient of 1:5), and therefore super critical flow conditions predominate at a discharge rate of 1.7 x 10-3 m3/s, which induces a substantial hydraulic jump. This experiment shows that the fishway efficiency under these conditions is greatly reduced. All five fish species, however, still had individuals that were able to successfully negotiate the channel under these conditions, albeit at relatively low numbers.

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Table 2-5: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:5 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 335.3 304.0 298.1 295.2 144.3

Vs (m/s) 1.41 1.16 1.08 0.98 0.69 Species Mean SD Mean SD Mean SD Mean SD Mean SD A. sclateri (n = 10) 13.33 5.77 43.33 5.77 70.00 30.00 63.33 25.17 73.75 19.96 B. anoplus (n = 10) 13.33 11.55 13.33 15.28 60.00 20.00 56.67 15.28 58.75 24.16 L. aeneus (n = 10) 6.67 5.77 30.00 26.46 90.00 10.00 86.67 15.28 83.75 30.68 L. capensis (n = 10) 26.67 5.77 43.33 15.28 86.67 5.77 90.00 10.00 85.00 20.00 T. sparrmanii (n = 10) 3.33 5.77 30.00 10.00 63.33 20.82 70.00 10.00 76.25 26.69

Abbreviations: Q (discharge); Pv (turbulence); Vs (velocity)

As mentioned, as the discharge rate increases, the turbulence levels tend to decrease due to an increased water volume within each pool, but only when the discharge is sufficient to satisfy submerged flow conditions. At this relatively flatter gradient (1:5), the channel tended toward submerged flow conditions as the channel at this gradient required less discharge volume to induce submerged flow conditions. The success rate of deeper-bodied, compressed body shape of T. sparrmanii increased at the higher discharge rates. This is assumed to be due to the increased water depth within the pools as well as within the slot itself, allowing for more efficient swimming of this species. This concurs with the results from Bermúdez et al. (2010), who reported on minimum water depth requirements for deeper-bodied fish species and who also noted that compressiform body-shaped species require a minimum water depth for successful passage through a fishway. It should be noted, however, that this species was also able to negotiate passage under super-critical flow conditions, albeit at a relatively lower success rate (0.3% success rate of the overall test population for this species). The success rates of all individuals of all the species showed a marked improvement when the flow rate was increased from 0.0050 m3/s to 0.0067 m3/s, with no further improvement of the success rate with the increased flow rates. It should be noted that 0.0067 m3/s represents 24.9% of the discharge volumes required to induce submerged flow hydraulic conditions. From the results of this set of experiments, it can be seen that discharge rates of below 0.0067 m3/s renders the experimental fishway channel only partially functional.

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2.3.4.2. Experiment 2: Vertical slot with 100 mm sills

This experiment utilised the standard vertical slot design presented in Figure 2-1, with the modification of fitting a 100 mm sill within each vertical slot opening to create a hybrid design between the standard vertical slot type fishway and the pool and weir- type fishway (“pool and slot” fishway). It was postulated that the fitting of sills into the vertical slots at each pool would allow each pool to retain enough water to aid upstream migration through the channel, even at the relatively low discharge rates that would normally be conducive to only super critical hydraulic conditions in a standard vertical slot fishway. The placement of the sills within the slot openings influences hydraulic characteristics of a vertical slot channel and are therefore reported on separately. These hydraulic conditions are presented in Figure 2-11.

Table 2-6 and Figure 2-11 show that the placement of a 100 mm sill in each slot reduces the turbulence levels in each pool. This is because the pools retain a minimum volume because of the sills and at the lower discharge rates the greater pool volume is more effective at dissipating the kinetic energy of the flowing water. The turbulence does, however, increase substantially as the discharge volume increases until submerged flow conditions are reached, after which the turbulence levels will increase less dramatically. At a gradient of 1:3, the fishway was seen again to be largely non-functional at discharge values of 0.0017 m3/s, with only the stronger- swimming species (L. aeneus and L. capensis being able to negotiate the channel under these conditions) (Figure 2-12). These hydraulic conditions seemingly exclude T. sparrmanii, A. sclateri and B. anoplus, which are regarded as the weaker swimming species of the test population (Table 2-6 and Figure 2-12). This is thought to be due to the lack of sufficient water volume that would allow weaker-swimming species to cross over the sills that separate the pools.

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Figure 2-11: Hydraulic variables for the standard vertical slot type of fishway with the placement of a 100 mm sill in each slot opening between pools at a gradient of 1:3, 1:4 and 1:5. The shaded areas indicate when the discharge volume is not sufficient to support submerged flow conditions.

Figure 2-12: Results of the experiments using a vertical slot fishway channel with the addition of 100 mm sills in each slot opening between all successive pools at three different gradients at varying discharges under laboratory conditions. Fish species abbreviations are given in Appendix B

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Table 2-6: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:3 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 17.6 46.9 61.2 73.1 119.3

Vs (m/s) 0.69 0.98 1.08 1.16 1.40 Species Mean SD Mean SD Mean SD Mean SD Mean SD

A. sclateri (n = 10) 0 0 0 0 3.33 5.77 10.00 10.00 11.25 13.56 B. anoplus (n = 10) 0 0 0 0 10.00 10.00 10.00 17.32 21.25 17.27 L. aeneus (n = 10) 3.33 5.77 13.33 11.55 13.33 11.55 26.67 23.09 37.50 22.52 L. capensis (n = 10) 20.00 10.00 23.33 32.15 23.33 5.77 43.33 15.28 66.25 24.46 T. sparrmanii (n = 10) 0 0 0 0 10.00 17.32 16.67 20.82 30.00 22.68

Abbreviations: Q (discharge); Pv (turbulence); Vs (velocity)

An improvement of success rate can be seen as the discharge volume increases. The fishway at this gradient and discharge volumes provided by the test conditions is not thought to be functional and would not provide sufficient means to traverse a barrier. These results indicate that placing a sill within the slot openings of a fishway channel at a gradient of 1:3 at low discharge rates does not improve functionality of the fishway over a standard vertical slot fishway. Although not tested, if extremely low discharge volumes are expected to occur, it is recommended that smaller sills be utilised. Again, a general improvement of functionality of the fishway can be noted with increased discharge volumes. Table 2-7 presents the results of when the channel was evaluated at a gradient of 1:4.

Table 2-7: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:4 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 12.9 34.5 45.0 53.8 87.9

Vs (m/s) 0.069 0.977 1.079 1.155 1.401 Species Mean SD Mean SD Mean SD Mean SD Mean SD

A. sclateri (n = 10) 6.67 5.77 26.67 5.77 56.67 25.17 60.00 20.00 51.25 30.44 B. anoplus (n = 10) 26.67 15.28 36.67 11.55 43.33 20.82 46.67 11.55 43.75 17.68 L. aeneus (n = 10) 16.67 15.28 40.00 10.00 53.33 25.17 80.00 10.00 83.75 14.08 L. capensis (n = 10) 20.00 0 26.67 20.82 76.67 23.09 73.33 5.77 91.25 11.26 T. sparrmanii (n = 10) 6.67 11.55 13.33 15.28 36.67 5.77 26.67 5.77 50.00 22.04

Abbreviations: Q (discharge); Pv (turbulence); Vs (velocity)

The flatter gradient allowed for smaller changes of heights between successive pools, which indicates that the water entering into a pool had a relatively lower velocity than 112 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

when the channel was set at a gradient of 1:3 and results in the lowered turbulence levels. An improvement in the passing of a greater proportion of the test population of fish was noted for this experiment, most noteworthy being at the lower discharge volumes. Again, the success of the fishway was improved with increased discharge volumes.

Table 2-8 presents the results of the experiments undertaken with the channel set at a gradient of 1:5. Further overall improvement of functionality can be seen from the results at all discharge values, with the successful passing of individuals of all species, even at the lower discharge volumes. Seemingly optimal results were gained when the discharge volumes exceeded 0.0067 m3/s.

Once again, an increase in utilisation of the channel was noted as the channel tended toward submerged hydraulic conditions, and, once these conditions were reached, no noteworthy differences in utilisation by the various species at increased flow rates were noted. There was a large standard deviation of the results observed throughout the experiments as shown in Table 2-3 to Table 2-8, which highlights the unpredictable and often erratic responses of the fish to the induced swimming experiments.

Table 2-8: Results of the experiment using a vertical slot experimental channel in the laboratory at a gradient of 1:5 at five discharge rates.

Replicates Q (m3/s) 0.0017 0.0050 0.0067 0.0082 0.0149

3 Pv (watts/m ) 86 138.5 171 182.8 215.4

Vs (m/s) 0.652 0.95 1.07 1.164 1.401 Species Mean SD Mean SD Mean SD Mean SD Mean SD

A. sclateri (n = 10) 40.00 20.00 46.67 11.55 83.33 15.28 73.33 23.09 78.75 20.31 B. anoplus (n = 10) 40.00 10.00 63.33 25.17 83.33 20.82 93.33 5.77 72.50 21.88 L. aeneus (n = 10) 46.67 11.55 56.67 28.87 80.00 0.00 90.00 10.00 92.50 8.86 L. capensis (n = 10) 40.00 34.64 63.33 15.28 86.67 5.77 93.33 5.77 91.25 11.26 T. sparrmanii (n = 10) 56.67 49.33 73.33 11.55 93.33 5.77 86.67 23.09 87.50 12.82

Abbreviations: Q (discharge); Pv (turbulence); Vs (velocity)

2.3.4.3. Experiment 3: Vertical slot with 100 mm sills and pebble substrate

Experiments where a pebble substrate (average diameter of 80 to 100 mm) was placed along the bottom throughout the length of the channel as an addition to the sills were

113 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION undertaken. The pebbles displace water and therefore reduce the overall pool volume. This reduces the capacity to dissipate the kinetic energy within the pool. Overall turbulence within each pool is therefore higher. Hydraulically sheltered areas and counter currents are created through a pebble substrate, which could be advantageous to smaller fish species and aquatic macro-invertebrates. The water volume that the pebbles displace means that there is less water volume to dissipate the energy, thereby increasing the overall turbulence experienced within each pool. The pebble substrate, however, directs water flow through interstitial spaces and creates hydraulically sheltered areas, counter currents and resting areas, which also influences the turbulence levels within the pools. The turbulence levels could not be accurately determined due to this and are therefore not reported on. Aquatic organisms utilise different hydraulic conditions to their advantage (e.g. seeking areas where vertical velocity dominates over horizontal velocity would aid in fish and invertebrates maintaining position; or substrates that provide sheltered areas from turbulent flow) (Mallen-Cooper, 1996) and so variations such as these were undertaken in an effort to improve the internal hydraulics of a fishway by providing sheltered areas for both fish and invertebrates.

At the lower flow rates (0.0017 to 0.0082 m3/s), the pebbles were not completely submerged and the water flow was mainly through the interstitial spaces. Running the fishway at these lower flow rates did not yield any results as no fish negotiated the channel. Running at the higher flow rate (0.0149 m3/s) submerged the pebble substrate and, after running an experimental set (three separate one-hour intervals), only two L. capensis (85 mm and 95 mm TL) were noted to have made it successfully through the channel.

Although considered a viable method of enhancing fishway value, this experimental setup was abandoned as the experimental setup was found to be unsuitable to utilise a pebble substrate. The addition of a pebble substrate should only be considered for systems that can maintain adequate flow volumes to provide enough open water column for use by fish. A deep enough water column through the channel would mean lowered water velocity through the interstitial spaces between the pebbles, which would provide hydraulic sheltering for smaller fish, juvenile eels and macro-invertebrates, making is especially relevant to coastal fishways.

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2.4. CONCLUSIONS & RECOMMENDATIONS

In this chapter, individuals of various fish species representative of a broad spectrum of migratory groups were exposed to a vertical slot fishway under varying hydraulic conditions in order to ascertain the hydraulic conditions within a vertical slot channel that would allow for the successful passing of the majority of the test population. During the laboratory experiments, it was shown that some individuals of all species were able to successfully negotiate steeper gradients and more difficult hydraulic conditions. This was, however, limited to sporadic occurrences and is therefore not thought to be representative of the general test population. The experiments showed that a greater percentage of the test population of all species utilised for the experiments were able to negotiate the channel at the lower gradient of 1:5, and where a flow rate that provided sufficient volume within each pool was provided.

The provision of a sill within the slot openings provided for the persistence of a minimum volume within each pool. The retention of water within each pool allowed for submerged flow conditions to be reached with at relatively lower discharge rate than that for a standard vertical slot fishway channel. The placement of a sill within the slot opening showed an increase in the success rate of both proportions of the populations as well as a greater number of test species at lower flow rates (before submerged flow conditions were reached). This was shown to be true for the smaller and weaker- swimming species. These results indicate that the placement of a sill within the slot opening would improve the functionality of a fishway by providing both a greater pool volume at lower flow rates and to allow for passage of deeper-bodies fish species at the lower flow rates as well. This is useful for river systems that are strongly seasonal and where provision of flow volumes to allow for submerged flow cannot be assured. The experimental testing indicated that a large proportion of the individuals of the test population and a diversity of species from the Vaal River system could successfully negotiate a vertical slot fishway with the addition of sills in the base of each slot opening at a slope of 1:5.

The vast majority of fish species throughout South Africa actively migrate during the onset of the summer cycle when rivers are swollen following the first of the significant rainfall events (Skelton, 2001). Successfully simulating the complex interplay between climatic, physico-chemical and biological factors brought about during this seasonal 115 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION period within the laboratory was found to be unsuccessful in inducing the strong behavioural response of the fish that is observed under natural field conditions. This proved to be a limitation to laboratory testing of the channel that relied on the natural behavioural response of the test population. There is a strong will and drive that results in the strong swimming abilities of the fish under natural field conditions. Under laboratory conditions, the behavioural response had to be forcibly induced, which meant that the response was not as strong as it would be under natural field conditions, where fish are induced to swim as a response to environmental cues. Laboratory experimentation of novel fishway designs remains important as it is possible to determine their ecological functionality and viability for use, but this should only form a portion of the testing, which should be implemented under natural conditions to gain a greater confidence of the resulting data.

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2.5. REFERENCES

Amado, A.A. (2012). Development and application of a mechanistic model to predict juvenile salmon swim paths. Unpublished Ph.D. Dissertation, Department of Civil and Environmental Engineering, University of Iowa, Iowa City, United States. p. 106. Bainbridge, R. (1958). The speed of swimming fish as related to size and the frequency and amplitude of the tail beat. Journal of Experimental Biology, 35: 109-133. Bainbridge, R. (1960). Speed and stamina in three fish. Journal of Experimental Biology, 37: 129-153. Bermúdez, M., Puertas, J., Cea, L., Pena, L. and Balairón, L. (2010). Influence of pool geometry on the biological efficiency of vertical slot fishways. Ecological Engineering, 36: 1355-1364. Bizzotto, P.M., Godinho, A.L., Vono, V., Kynard, B. and Godinho, H.P. (2009). Influence of seasonal, diel, lunar, and other environmental factors on upstream fish passage in the Igarapava Fish Ladder, Brazil. Ecology of Freshwater Fish, 18: 461-472. Bok, A., Kotze, P., Heath, R. and Rossouw, J. (2007). Guidelines for the planning, design and operation of fishways in South Africa. WRC Report No. TT 287/07. Water Research Commission, Pretoria, South Africa. Calluaud, D., Cornu, V., Bourtal, B., Dupuis, L., Refin, C., Courret, D. and David, L. (2012). Scale effects of turbulence flows in vertical slot fishways: field and laboratory measurement investigation. In: Mader, H. and Kraml, J. (eds.). Conference proceedings of the 9th international Symposium on Ecohydraulics, September 2012, ISE 2012, Vienna, Austria. p. 10. Castro-Santos, T. (2005). Optimal swim speeds for traversing velocity barriers: an analysis of volitional high-speed swimming behavior of migratory fishes. Journal of Experimental Biology, 208: 421–432. Castro-Santos, T. (2006). Modeling the effect of varying swim speeds on fish passage through velocity barriers. Transactions of the American Fisheries Society, 135: 1230-1237. Castro-Santos, T., Cotel, A. and Webb, P. (2009). Fishway evaluations for better bioengineering: an integrative approach. American Fisheries Society Symposium, 69: 557–575. Chanson, H. and Murzyn, F. (2008). Froude similitude and scale effects affecting air entrainment in hydraulic jumps. World Environmental and Water Resources Congress May 12-16, 2008, Honolulu, Hawaii. pp. 1-10. 117 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

Clay, C.H. (1995). Designs of Fishways and Other Fish Facilities, 2nd edn. Lewis Publishers, CRC Press, Boca Raton, Florida. p. 248. Davies, B. and Day, J. (1998). Vanishing waters. University of Cape Town Press, Cape Town, South Africa. p 487. Hatry, C., Thiem, J. D., Binder, T. R., Hatin, R., Dumont, P., Stamplecoskie, K. M., Molina, J. M., Smokorowski, K. E. and Cooke, S. J. (2013). Comparative physiology and relative swimming performance of Three redhorse (Moxostoma spp.) species: Associations with fishway success. Physiological and Biochemical Zoology, 87(1): 148-159. Katopodis, C. (1992). Introduction to fishway design. Unpublished working document. Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, Canada. p. 62. Larinier, M. (2001). Environmental issues, dams and fish migration. In: Marmulla, G. (ed.). Dams, fish and fisheries: opportunities, challenges and conflict resolution. FAO Fisheries Technical Paper 419. Fisheries Resources Division, FAO Fisheries Department, Rome. Italy. pp. 45-89. Larinier, M., Travade, F. and Porcher, J.P. (2002). Fishways: biological basis, design criteria and monitoring. Bulletin Franҫais de la Pêche et de la Pisciculture, 364 (Suppl.): 208. Lepono, T., Kotse, P., Niehaus, B. and du Preez, H. (2000). Ecological effects of release of water from LHWP dams into Ash/Liebenbergsvlei system. Unpublished Report No. Potch/01/Hons. Potchefstroom University for Christian Higher Education, Potchefstroom, South Africa. p. 45. McLeod, A.M. and Nemenyi, P. F. (1941). An investigation of fishways. University of Iowa Studies in Engineering Bulletin, 24: 1-72. Mallen-Cooper, M. (1996). Fishways and freshwater fish migration in south-eastern Australia. Unpublished Ph.D. Thesis. University of Technology. Sydney, Australia. p. 377. Mallen-Cooper, M. (1999). Developing fishways for non-salmonid fishes: a case study from the Murray River in Australia. In: Odeh, M. (ed.). Innovations in fish passage technology. Bethesda, MD: American Fisheries Society. pp. 173-195. Northcote, T. G. (1998). Migratory behaviour of fish and its significance to movement through riverine fish passage facilities. In: Jungwirth M., Schmutz S. and Weiss S. (eds.). Fish Migration and Fish Bypasses. Fishing News Books, Oxford, UK. p. 113. Peake, S. (2004). An evaluation of the use of critical swimming speed for determination of culvert water velocity criteria for smallmouth bass. Transaction of the American Fisheries Society, 133: 1472–1479. 118 | P a g e CHAPTER 2: LABORATORY EXPERIMENTATION

Puertas, J., Cea, L., Bermúdez, M., Pena, L. Rodríguez, A., Rabuñal, J.R., Balairón, L., Lara, A. and Aramburu, E. (2012). Computer application for the analysis and design of vertical slot fishways in accordance with the requirements of the target species. Ecological Engineering, 48: 51-60. Rajaratnam, N., Van der Vinne, G., and Katopodis, C. (1986). Hydraulics of vertical slot fishways. Journal of Hydraulic Engineering, 112(10): 909-927. Rajaratnam, N., Katopodis, C. and Solanki, S. (1992). New designs for vertical slot fishways. Canadian Journal of Civil Engineering, 19: 402-414. Rodríguez, T.T., Agudo, J.P., Mosquera, L.P. and González, E.P. (2006). Evaluating vertical-slot fishway designs in terms of fish swimming capabilities. Ecological Engineering, 27: 37-48. Rodríguez, A., Bermúdez, M.J., Rabuñal, R., Puertas, J., Dorado, J., Pena L. and Balairón, L. (2011). Optical fish trajectory measurement in fishways through computer vision and artificial neural networks. Journal of Computing in Civil Engineering, 25: 291-301. Schwalme, K., Mackay, W.C., and Lindner, D. (1985). Suitability of vertical slot and Denil fishways for passing North-temperate non-salmonid fish. Canadian Journal of Fisheries and Aquatic Science, 42: 1815-1822. Silva, A.M., Ferreira, M.T., Santos, J.M., Pinheiro, A.N., Melo, J.F. and Bochechas, J. (2004). Development of a pool-type fishway facility for Iberian cyprinids. Proceedings of the 5th International Symposium on Ecohydraulics, Madrid, 12-17 September. pp. 942-947. Silva, A.T., Santos, J.M., Ferreira, M.T., Pinheiro, A.N., Katopodis, C. (2011). Effects of water velocity and turbulence on the behaviour of Iberian barbell (Luciobarbus bocagei, Steindachner 1864) in an experimental pool-type fishway. River Research and Applications, 27: 360–373. Skelton, P. (2001). A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa. p. 395. Tarrade, L, Pinneau, G., Calluaud, D., Texier, A., David, L. and Larinier, M. (2011). Detailed experimental study of hydrodynamic turbulent flows generated in vertical slot fishways. Environmental Fluid Mechanics, 11 (1): 1-21. Tarrade, L., Texier, A., David, L. and Larinier, M. (2008). Topologies and measurements of turbulent flow in vertical slot fishways. Hydrobiologia, 609: 177- 188. Videler, J.J. and Wardle, C.S. (1991). Fish swimming side by side: speed limits and endurance. Reviews in Fish Biology and Fisheries, 1: 23-40. Videler, J.J. (1993). Fish swimming. Chapman and Hall, London. p. 284.

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White, L.J., Harris, J.H. and Keller, R.J. (2011). Movement of three non-salmonid fish species through a low-gradient vertical- slot fishway. River Research and Application, 27: 499–510. Williams, J. G., Armstrong, G., Katopodis, C., Larinier, M. and Travade, F. (2012). Thinking like a fish: a key ingredient for development of effective fish passage facilities at river obstructions. River Research and Applications, 28: 407-417. Wu, S., Rajaratnam, N. and Katopodis, C. (1999). Structure of flow in vertical slot fishway. Journal of Hydraulic Engineering, 125(4): 351-359.

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DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT

MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH

AFRICA.

CHAPTER 3: Field trial testing using an experimental in situ scale model vertical slot fishway channel to validate and supplement laboratory experimental data

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3.1 INTRODUCTION

3.1.1. Background

Fish migrate to spawn, feed, reach rearing areas, and seek refuge from predators or harmful environmental conditions such as chemical pollution and seasonal temperature fluctuations (Katopodis, 1989; Gallagher, 1999; Lucas & Baras, 2001; Marmulla, 2001; Roscoe & Hinch, 2010; Baumgartner et al., 2014) and therefore it can be assumed that the objective of maintaining fish passage to allow for freedom of movement is to ensure the long term sustainability of fish populations (Fouché & Heath, 2013). The success of upstream migration within a river system is limited by the presence of barriers that can impede or even eliminate the passage of fish. If the migrating fish do make it upstream across difficult barriers, they are often too exhausted to spawn (Gallagher, 1999). If these fish are blocked from upstream passage and are forced to spawn in densely-populated downstream areas, their offspring may be forced to compete for any available rearing habitat, resulting in a greatly reduced reproductive capacity for those species. If migration is delayed or stopped by barriers, such as barriers only becoming passable under exceptionally high flows during periods that don’t coincide with breeding times, the life cycle may be disrupted resulting in limited populations (Gallagher, 1999). Besides meeting the immediate needs of seasonal spawning migrations of certain species, migratory freedom is required by all species of fish for long term maintenance of genetic diversity. Maintaining the longitudinal continuity of a river system is therefore vital to the ongoing survival of the important migratory fish species within that system. Potential barriers to upstream migration include natural structures such as waterfalls and naturally steep gradients, and artificial barriers such as culverts, weirs and dams. Barriers to migration occur through the interaction of topography (e.g. waterfalls, super critical flow over bedrock, naturally steep gradients), human structures (e.g. dams, gauging weirs), and the timing of rainfall and high stream flows (Bartson, 1997) as some waterfalls or cascades may become impassable at high flows, due to the increased water velocity, and at low flows, due to the lack of water volume and depth. The implementation of a fishway at an artificial migratory barrier has become the standard mitigation measure to overcome fragmentation of riverine habitat (Bok et al., 2007). Each fish species has different swimming and leaping abilities, so that a barrier for one species may be passable by others (Gallagher, 1999). It is important therefore to gain an understanding of the swimming and jumping abilities of a target community of fish species in order to design a fishway with optimal hydraulic

122 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY parameters that allow fish to migrate upstream easily without expending excessive time and suffering fatigue. Little information is available on the preferences and abilities of South African species when it comes to the selection and design of fishways for South African rivers (Bok et al., 2007). In order to develop the knowledge base of fishway design within South African rivers, it is imperative to thoroughly test various fishway prototype designs over a broad spectrum of fish species (or groups of similar species with relatively similar migratory potentials) to make it functional to all of the important migratory fish within a system.

A dataset in terms of hydraulic conditions within a vertical slot fishway was compiled in Chapter 2 for a test population of fish maintained under laboratory conditions. Laboratory-based experimentation has long been the basis of determining the swimming abilities of these species (Pon, 2008), but this type of testing has also been found to be an under-estimation of the swimming capacities of these species (Bunt, 2001; Peake, 2004). Laboratory-based experimentation therefore sets a conservative benchmark value for maximum swimming capabilities for these species. It can be argued that this under-estimation allows for a safeguard that will allow for maximum conservation of longitudinal connectivity of a system, but an overly-conservative approach to fishway designs has limitations where budget constraints are to be considered and a compromise between optimal ecological functionality and design and budget limitations often has to be sought.

It has been well documented that fish undertake the strongest potadromic migratory movements following the first rains of the summer season (in summer rainfall areas) when rivers are in spate (Skelton, 2001). This event coincides with a multitude of environmental, climatological, chemical and physical changes within an aquatic system, which would then govern the instinctual swimming and migrational behaviour patterns of the fish within that system. These changes include (amongst others) the river water getting gradually warmer due to the onset of summer, to get suddenly cooler from isolated rainfall events; chemical changes within the system brought about from dilution by rainwater; the day length getting gradually longer and sunlight more intense (Marmulla, 2001; Roscoe & Hinch, 2010; Baumgartner et al., 2014) that would increase the productivity of a system and therefore the food availability for fish; the river volumes increasing, together with discharge rates, water velocity and turbulence levels; increased habitat availability due to increased river channel volumes; and the drowning out of many obstacles that are migratory barriers under low flow conditions. These are 123 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY factors that work independently, or synergistically to induce seasonal and cyclic spawning migrations, which are thought to induce the strongest swimming capabilities within fish communities. This complex scenario cannot be holistically simulated under controlled laboratory conditions, and fish maintained under laboratory conditions that are used for fishway testing and the determination of maximum swimming capacities are therefore not exposed to the strong environmental cues that govern migrational movements. This makes for an overall weaker response to those stimuli offered under laboratory conditions relative to the strength of the response under natural conditions. The swimming capabilities and potential of the fish as determined under laboratory conditions are therefore thought to be an under-estimation of their true swimming strengths and free-swimming capabilities (Booth et al., 1997; Peake, 2004). (Also see Chapter 2 – Laboratory experiments).

3.1.2. Aims and objectives

The aim of this chapter was to validate data that were gathered through the laboratory testing of the experimental fishway channel (Chapter 2) under actual field conditions using fish that are undergoing active migrations. The field testing of the experimental fishway channel is aimed at fish species of the Highveld (within the Vaal River system) as well as the Lowveld (within the Sabie River system) areas. The inclusion of the two river systems from two different climatic regions was to diversify the target species as far as possible. These data would serve to expand on the knowledge base on the migrational behaviour and swimming potential of a greater diversity of indigenous South African fish species.

3.2. SITE SELECTIONS & CHARACTERISTICS

In both cases for the Sabie River and Vaal River, site selection was based on the same criteria: (a) the tests were conducted where fish were known to congregate at a migratory barrier; (b) reasonable access for a vehicle was required due to the cumbersome nature of the field equipment and the experimental setup; and (c) the river site also needed to incorporate a diversity of habitat biotopes to improve the possibility of collecting a greater diversity of fish species for inclusion in the testing protocols. These factors also ensured for collection of sufficient numbers of test fish already naturally stimulated to migrate and therefore conditioned to potentially overcome migratory barriers if it was found that the channel could not be placed directly into the river. 124 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

3.2.1. Sites in the Vaal River

Three sets of experiments were undertaken at the Vaal River. Two of these were located at the same site, which was at the DWS gauging weir (C2H003) at Elandsfontein/ Engelbrechtsdrift (Vischgat), located midway between the Vaal Barrage and the Vaal Dam, within the Upper Vaal DWS Water Management Area (WMA) (DWAF, 2009) (Figure 3-1). The Vaal River is a large, perennial system. Flow volumes fluctuate seasonally, but the system is influenced by the management of major impoundments located upstream, such as the Vaal Dam. Water and habitat quality are subject to transformation and degradation through urbanisation, mining, agriculture and water-borne effluents of poor quality (DWAF, 2009).

Figure 3-1: Localities of the survey sites on the Vaal River.

Fish species are exclusively potadromous, with the main migratory groups including yellowfish (Labeobarbus spp.), and mudfish (Labeo spp.). Other species that undertake more local migrations include a diversity of Barbus spp., representatives of the family Cichlidae (Tilapia sp. and Pseudocrenilabrus sp.), catfish (Clarias sp. and Austroglanis sp.). Many exotic species also occur within the system, including

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Cyprinus carpio (Common carp), Micropterus salmoides (Largemouth bass), Micropterus dolomieu (Smallmouth bass), Gambusia affinis (Mosquitofish) and Ctenopharyngodon idella (Grass carp) (Skelton, 2001; Scott et al., 2006; Kleynhans et al., 2007).

The DWS gauging weir C2H003 is a sharp crest weir measuring approximately 3 m in height (Figure 3-2), which creates an upstream impounding impact to the river at the site. Downstream of the site, the watercourse is characterised by rapids, riffles and glides within a braided and multi-channelled watercourse interspersed with reed islands and sandbanks. A diversity of flow velocities and water column depths exist downstream of the weir (Figure 3-3).

Figure 3-2: The flow-gauging structure Vaal River at the Vischgat (Engelbrechtsdrift) site that presents a migration barrier to fish within the system.

The habitat at the site presupposes that stronger-swimming species would be present. Backwaters were also present at the site, so a diversity of fish species representative of the system was expected to be present and congregating at the base of the weir.

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Figure 3-3: Typical habitat at the Vaal River at the Vischgat (Engelbrechtsdrift) site.

The third survey on the Vaal River was conducted at Eendekuil Fly-fishing Resort approximately 15 km upstream of the town of Parys. No migratory barrier was present at this site, but, again, a diversity of habitat units meant that a diversity of fish species was expected to occur. The localities of the sites are presented in Table 3-1.

Table 3-1: Sampling sites selected in the Vaal River for the various field assessments.

GPS co-ordinates Site name River Site/barrier description Latitude (S) Longitude (E) Mixed riffle, run, glide, pool & Eendekuil Fly- Vaal backwaters habitat. Gauging Weir 26° 47’ 12.42” 027° 30’ 31.7” fishing resort River C2H140 Vischgat (DWS Vaal DWS sharp-crest gauging weir Gauging Weir 26°49’11.0” 28°03’49.0” River (decommissioned) C2H003)

The Vaal River falls within the Orange-Vaal migratory region (DWAF, 2009). The sites were selected as they consisted of a mixture of fast shallow and fast deep aquatic habitats, typified by small waterfalls, rapids and glides. The substrate found throughout this habitat was predominately cobbles and gravel, with a small proportion of discontinuous bedrock. The presence of islands and braided channelling increased the hydraulic variability of the channel, which increased the diversity of physical habitat (such as sandbank formation and sheltered areas). Typical habitat features of the site

127 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY are presented in Figure 3-4). This diversity of habitat biotopes and velocity-depth classes was aimed for in a survey area as the fish inhabiting the faster-flowing water presupposes species and individuals that would typically undertake routine migrations, whilst those species that inhabited well-vegetated and quieter areas are thought to be representative of weaker-swimming species within the system. Fish species that were expected in the area, based on the habitat present, were L. aeneus, L. capensis, B. trimaculatus and A. sclateri. Well-vegetated quieter backwaters within this study site were expected to support B. paludinosus, T. sparrmanii and P. philander (Skelton, 2001; Kleynhans et al., 2007). Main migratory groups found within this system include the potadromous species of the genera Labeobarbus, Barbus and Labeo. Key migratory species found within the Vaal system are Labeo kimberleyensis (Vaal- Orange largemouth yellowfish), B. paludinosus, B. trimaculatus, L. capensis and Labeo umbratus (Moggel). Labeo umbratus and L. kimberleyensis were not expected, however, due to the unsuitability of the habitat at the sites.

Figure 3-4: Typical habitat at the Vaal River at the Eendekuil site.

3.2.2. Sabie River

Three field surveys were undertaken at the Sabie River within the Kruger National Park; two being at the Kruger Gate DWS gauging weir (X3H021) with the other one survey undertaken at Sabiepoort, located just downstream of the confluence between

128 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY the Sabie River and Mnondozi River (Table 3-2). The study site localities are shown in Figure 3-5.

Table 3-2: Sampling sites selected in the Sabie River for the various field assessments.

GPS co-ordinates Site name River Site/barrier description Latitude (S) Longitude (E)

Mixed riffle, run, glide, pool & Sabiepoort Sabie River 25° 09’ 47.3” 32° 00’ 14.5” backwaters habitat Kruger Gate DWS gauging weir downstream (DWS Sabie River of Kruger Gate, upstream of 24° 58’ 6.5” 31° 30’ 55.5” Gauging Weir Skukuza Rest Camp. X3H021)

Figure 3-5: Localities of the survey sites on the Sabie River.

The gauging weir structure at Kruger Gate (X3H021) (Figure 3-6) acted as a migration barrier at the time of the survey resulting in the concentration of fish directly downstream from the barrier. It was evident that the fish were stimulated to migrate and attempted to negotiate the barrier at various points (Figure 3-7).

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Figure 3-6: DWS weir (X3H021) in Sabie River located downstream of Kruger Gate.

Figure 3-7: Congregation of a diversity of fish species at the Sabie River site opportunistically trying to negotiate passage upstream across the weir within peripheral zones of the watercourse.

Due to much of the Sabie River running through the formal conservation area of the Kruger National Park, it was expected to support a large diversity and number of fish (Weeks et al., 1996). Flow in the Sabie River varies seasonally, with summer peaks (February) and low flows at the end of the dry season (October). Zero flow conditions have never previously been recorded for the Sable River. The water quality is

130 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY generally considered to be good to excellent but the pH is relatively low and the system is therefore poorly buffered and sensitive to changes in the catchment (Chunnett, Fourie & Partners, 1990). The Sabie River falls within the lower Limpopo, Incomati and Pongola migratory region (an interconnected river system that allows freedom of migration for the mobile aquatic biodiversity that it supports) and forms part of the Incomati River system (DWA, 2009). Main migratory groups found within this system include the catadromous eels of the Anguillidae family and varius potadromous species, which include the genera Hydrocynus, Labeobarbus, Barbus, Chiloglanis and Labeo. Key migratory species expected to be found were Anguilla mossambica (Longfin eel), Anguilla marmorata (Giant mottled eel), Anguilla benghalensis labiata (African mottled eel), Anguilla bicolor bicolor (Shortfin eel), Hydrocynus vittatus (Tigerfish), Labeobarbus marequensis (Lowveld largescale yellowfish), Labeobarbus polylepis (Bushveld smallscale yellowfish), Labeo rosae (Rednose labeo), Labeo ruddi (Silver labeo), Labeo congoro (Purple labeo), Labeo cylindricus (Redeye labeo), Labeo molybdinus (Laeden labeo), Chiloglanis paratus (Sawfin suckermouth), Chiloglanis anoterus (Pennant-tailed suckermouth), Chiloglanis swierstrai (Lowveld suckermouth), and various Barbus species. Catadromic macro-crustaceans of the genius Macrobrachium also occur within the system (Skelton, 2001; Scott et al., 2006).

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3.3. MATERIALS & METHODS

3.3.1. Description of the experimental fishway setup and design

The basic test facility used in the field for these experiments consisted of a headway (upper) tank of approximately 1.2 m (long) x 0.8 m (wide) x 0.8 m (deep). A lower collection tank of similar dimensions was at the end of the channel. These two tanks were connected with a channel measuring 0.380 m wide by 0.4 m deep that incorporated baffles in the configuration of a typical vertical slot-type fishway. The basic test setup is presented in Figure 3-8.

Figure 3-8: The basic experimental setup of the vertical slot fishway utilised for the field experiments, showing the headway tank connected to the lower collection tank, with a water pump that circulates water through the channel.

The vertical slot channel configuration was per the design specifications shown in Figure 3-9, with each pool measuring 0.380 m (W) x 0.445 m (L). The gradient of the channel in between the two tanks could be adjusted to suit the needs of the experimental protocols, but was often limited by the terrain at the experimental localities. The experimental localities were always on the banks of a river, which meant that steep slopes and uneven surfaces had to be accommodated.

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0.85A 1.15A 2.08A A

0.41A

6.63A 1.78A 0.42A

0.41A

8.11A

Figure 3-9: The relative dimensions of a single pool of the experimental vertical- slot fishway channel used in this study (adapted from Larinier et al., 2002). Flow direction is from right to left. All the dimensions of the fishway are given relative to the slot opening width, identified as “A” in figure and the dimensions of each successive pool are repetitious of the one that precedes it.

Where site conditions allowed, the end of the channel was placed directly onto the river at the base of a migratory barrier and fish were observed to have been congregating. The headway tank remained connected to the channel so that fish that successfully negotiated the channel could be collected. A water pump was used to pump water from the river into the headway tank that would then flow through the experimental channel (Figure 3-10). This experimental procedure was followed where fish were observed to be already undertaking active migrations. Fish within the river were observed to congregate at the base of a migratory barrier and were actively seeking a means to gain access across the barrier to continue upstream passage. By placing the channel within the water at this point and pumping water through it, fish were induced to swim up the channel as it provided a means to gain access across the barrier. This experimental type fortuitously made use of fish that were already actively migrating and did not require that the fish were first captured and placed within the experimental system. Capture stress was avoided in this way. The fish were only captured out of the header tank once they had successfully negotiated the fishway channel, identified, the age class (juveniles or adults) determined and returned to the river. There was no way of determining the population size within the river and therefore no way of determining the proportion of successful fish relative to the unsuccessful attempts by fish. High ambient temperatures meant that during the survey fish could not be

133 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY detained for prolonged periods to avoid a high number of fatalities. This was important whilst working within a conservation area.

The water was pumped for a set time period from the river into the top tank, and, upon completion of the experiment, the pump was stopped, the top tank was drained of water via a sump plug and the fish were captured, identified, counted, measured and released back into the river. The channel was set at various gradients to test the hydraulic parameters that the fish were able to overcome through a variety of experimental protocols. The pump had a capacity of approximately 0.015 m3/s, which was the standard discharge rate utilised for all field experiments. The experimental design was largely dependent on site conditions and the channel was only placed directly into the river where site conditions could accommodate it and where the top tank could be safely stabilized and levelled as well. These very specific site requirements meant that few opportunities were afforded to this experimental protocol.

Figure 3-10: Where site conditions allowed for it, the end of the experimental channel was placed directly into the river.

The experimental fishway channel and both tanks were designed to stack together for ease of transport to various sites. This was the same channel that was utilised for the

134 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY laboratory-based experiments (Chapter 2). All experimental replicates were limited to approximately 60 minutes.

3.3.2. Collection and acclimation of fish

At all the sites, fish were collected from the associated river by standard electronarcosis using a 2.5 kVA AC generator, extension cable, electrodes and dip nets. Cast netting techniques were used when the experimental channel could not be placed directly into the river. Seine netting was also employed as a collection technique where the habitat type allowed for it. All of the fish collected were allowed time to acclimate to the conditions within the lower water tank, and the water circulating patterns, prior to allowing them access up the experimental fishway channel for up to one hour prior to the starting the trial replicates.

3.4. RESULTS & DISCUSSIONS

3.4.1. Hydraulic conditions of the experimental channel

The gradient of the channel in between the headway tank and the collection tank could be adjusted to suit the needs of the experimental protocols, but was often limited by the terrain at the experimental localities. The experimental localities were always on the banks of a river, which meant that steep slopes and uneven surfaces had to be accommodated, whilst remaining stable enough and safe for the operators to work around. The experimental channel was divided into nine separate pools, each measuring 0.380 m (W) x 0.445 m (L). The slot width throughout the channel was 0.05 m. A vertical slot with pools of these dimensions theoretically caters for fish equal and smaller than one third of the length of the bucket (i.e. 0.1483 m TL) (Bok et al., 2007).

A petrol water pump was utilised to circulate the water through the fishway channel for each experiment. This pump induced a discharge rate of approximately 0.015 m3/s, which was the maximum pumping capacity that could be attained during the laboratory experiments (Chapter 2). Different gradients of the channel were tested according to what site conditions would allow for, which were often uneven or not stable enough to allow for safe operation. The different gradients of the channel induced different hydraulic conditions within the channel, which are presented in Table 3-3. This is a

135 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY combined summary of the hydraulic conditions of the channel for the Sabie River and Vaal River experiments. It can be seen that submerged flow conditions for this channel at a discharge rate of 0.015 m3/s are induced at a channel gradient of 1:5 or lower (flatter).

3.4.2. Results of field trial replicates

3.4.2.1. Vaal River

The results of the field-testing are reported in Table 3-4. As mentioned, three different field trips were undertaken to test the experimental fishway channel to the Vaal River. Locality 1 (Eendekuil) was undertaken as a single day trip, whereas the two different trips to Vischgat were undertaken over a period of more than one day. Different numbers of fish were used as they became available (captured), and some individuals that were observed to be under undue stress or fatigued were released back into the river and replaced with newly-captured individuals. This explains the differing numbers and size ranges of individuals used for these experiments.

Table 3-3: Summary of the hydraulic characteristics of the experimental vertical slot fishway channel under field conditions for both the Vaal River and Sabie River experiments.

3 3 Submerged flow Gradient Q (m /s) Vs (m/s) DH (m) Pv (watts/m ) conditions reached 1:3.15 0.015 m3/s 1.412 0.159 603.4 No 1:3.60 0.015 m3/s 1.412 0.139 505.1 No 1:3.80 0.015 m3/s 1.412 0.132 472.7 No 1:4.00 0.015 m3/s 1.412 0.125 441.1 No 1:4.20 0.015 m3/s 1.412 0.119 414.8 No 1:4.90 0.015 m3/s 1.412 0.102 343.7 No 1:5.00 0.015 m3/s 1.401 0.100 338.8 Yes 1:5.70 0.015 m3/s 1.314 0.088 270.5 Yes 1:6.90 0.015 m3/s 1.189 0.072 192.3 Yes 1:7.00 0.015 m3/s 1.172 0.070 212.5 Yes 1:7.50 0.015 m3/s 1.147 0.067 170.6 Yes 1:7.70 0.015 m3/s 1.129 0.065 162.3 Yes 1:8.40 0.015 m3/s 1.085 0.060 142.5 Yes 1:10.0 0.015 m3/s 0.990 0.050 106.2 Yes 1:10.8 0.015 m3/s 0.950 0.046 93.10 Yes 1:11.0 0.015 m3/s 0.940 0.045 89.9 Yes

Q=Discharge; Vs=Water velocity through the slot opening; DH=Difference in water levels between successive pools;Pv=Turbulence within each pool.

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Table 3-4: Fish species to successfully negotiate the vertical slot type fishway at the given gradients during experiments at the Vaal River. The standard lengths (SL) (mm) ranges are given in brackets. A summary of the hydraulic conditions at the given gradients is also provided.

Experiment Experiment 1 Experiment 2 Experiment 3 M=1:3.8 M=1:4.9 M=1:7 M=1:5.7 M=1:6.9 M=1:4.2 M=1:7.5 M=1:8.4 M=1:10.8 V =1.412 V =1.412 V =1.172 V =1.314 V =1.189 V =1.412 V =1.147 V =1.085 V =0.95 Channel s s s s s s s s s DH=0.132 DH=0.102 DH=0.070 DH=0.088 DH=0.072 DH=0.119 DH=0.067 DH=0.060 DH=0.046 conditions Pv=472.7 Pv=343.7 Pv=212.5 Pv=270.5 Pv=192.3 Pv=414.8 Pv=170.6 Pv=142.5 Pv=93.10 SF=No SF=No SF=Yes SF=Yes SF=Yes SF=No SF=Yes SF=Yes SF=Yes Locality* 1 1 1 2.1 2.1 2.2 2.2 2.2 2.2 ASCL (90-160) ASCL (90-175) ASCL (100-160) ASCL (100-160) (No=9; Ns=5) (No=10; Ns=9) (No=6; Ns=2) (No=6; Ns=4) BAEN (200-300) BAEN (97-165) BAEN (215-285) BAEN (215-220) (N =5; N =4) (N =6; N =4) Fish o s o s LCAP (70-300) (N =9; N =5) (N =7; N =4) BANO (54-56) BANO (54-56) individuals, o s o s (N =12; N =9) BANO (54-56) BANO (54-56) (N =7; N =6) (N =7; N =6) numbers and BAEN (90- o s BAEN (245- o s o s BAEN (90-180) BAEN (90-180) BAEN (180) (N =7; N =5) (N =7; N =3) BPAU (50-70) BPAU (50-70) size ranges 180) (N =7; 364) o s o s o (N =7; N =7) (N =7; N =7) (N =11; N =10) BPAU (50-70) BPAU (50-70) (N =7; N =3) (N =5; N =2) that N =4) o s o s o s (N =7; N =4) o s o s s BPAU (45-50) BPAU (45-50) ASCL (140-170) o s (N =7; N =3) (N =7; N =2) CGAR (200) CGAR (200) successfully BPAU (45-50) LCAP (82-190) o s o s (N =4; N =2) (N =4; N =2) (N =4; N =3) LCAP (75-200) LCAP (75-200) (N =1; N =1) (N =1; N =1) negotiated (N =4; N =0) o s o s o s (N =14; N =11) o s o s o s TSPA (60-70) o s (N =11; N =8) (N =11; N =9) LCAP (78-340) LCAP (78-340**) the fishway o s o s (N =5; N =3) PPHI (50-66) PPHI (50-66) (N =11; N =10) (N =11; N =9) channel o s o s o s (No=3; Ns=1) (No=3; Ns=1) PPHI (50-66) TSPA (97-165) TSPA (97-165) TSPA (97-165) (No=3; Ns=2) (No=5; Ns=5) (No=5; Ns=4) (No=5; Ns=5) TSPA (97-125) PPHI (50-66) (No=5; Ns=2) (No=3; Ns=2)

3 M=Channel gradient; Vs=Water velocity through slot (m/s); DH=Change in water level from one pool to the next (m); Pv=Turbulence (watts/m ); SF=Submerged flow conditions (yes/no). No=number of individuals of each species used for each experiment; Ns=number of successful individuals per experiment. Fish species abbreviations are given in Appendix B. *Locality: 1=Vaal River at Eendekuil; 2=Vaal River at Vischgat (2.1=trip 1; 2.2=trip 2).

137 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

3.4.2.1.1 Trial replicate 1

Trial replicate 1 was undertaken at Eendekuil on the Vaal River. The experimental setup was a closed circulation system as site conditions did not allow for the channel to be placed directly into the river. Fish therefore had to be collected from the river and placed within the system for an acclimation period of approximately 60 minutes prior to running the first experiment. A total of seven L. aeneus (five adults and two juveniles) and four B. paludinosus (all adults) were utilised (Table 3-4). Individuals measuring greater than 100 mm (SL) and 45 mm (SL) for L. aeneus and B. paludinosus, respectively, were considered as adults. Three gradients were tested, all with a constant discharge of 0.015 m3/s, with the system circulating for 60 minutes for each experimental condition.

Figure 3-11 presents the percentage of individuals of each species that successfully negotiated the channel (indicated in the figure as “positive” results) in relation to the percentage of the individuals of each species that remained in the lower holding tank (indicated in the figure as “negative” results). It could not be accurately determined if the individuals that remained in the lower tank actually attempted to swim up the channel and were limited by the hydraulic conditions, or that no attempt was made due to other undetermined variables such as capture stress. There is a low confidence level associated with the results of this experimental replicate, as capture stress was expected to reduce the stimulation and desire to attempt to negotiate the channel.

At a gradient of 1:3.8, approximately 57% (four of the seven individuals) of the L. aeneus individuals negotiated the channel, of which five were adults and two were juveniles. No B. paludinosus negotiated the channel. It was postulated that this was due to latent capture stress and lack of acclimatisation to the experimental system as this species was shown to successfully negotiate this channel gradient at the Sabie River during experiments when fish were actively migrating and were not captured prior to experimentation. It is also assumed that B. paludinosus, being a small-bodied species, would be more prone to predation and therefore would seek refuge for a longer period than a predatory and larger-bodied species such as L. aeneus, which would make for their reluctance to break cover under unfamiliar circumstances.

138 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

Figure 3-11: Results of trial replicate 1 at the Vaal River (Eendekuil). Fish species abbreviations are given in Appendix B.

At a gradient of 1:4.9, it can be seen that 100% of the L. aeneus test population (five adults and two juveniles) successfully negotiated the channel, with an improved success rate from 0% to 50% for the test population for B. paludinosus, of which four adult individuals were used. When the gradient of the channel was lowered to 1:7, again 100% and 50% of the L. aeneus and B. paludinosus test population, respectively, were successful in negotiating the fishway channel.

These results indicate that a small-bodied species such as B. paludinosus is able to negotiate the hydraulic conditions that were imposed by the channel set at a gradient of

3 1:4.9 (Vs = 1.412 m/s; DH = 0.102 m; Pv = 343.7 watts/m ), albeit at a 50% success rate. This success rate did not improve at lower gradients and therefore it is assumed that factors besides hydraulic conditions (e.g. capture and handling stress) led to limited positive results. It was shown that both adult and juvenile L. aeneus are able to 139 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY successfully negotiate the hydraulic conditions imposed by the channel set at a gradient of

3 1:3.8 (Vs = 1.412 m/s; DH = 0.132 m; Pv = 472.7 watts/m ). Success rates for this species did improve with a flatter gradient, however, indicating that the hydraulic conditions at steeper gradients did hamper the movement of the fish.

3.4.2.1.2. Trial replicate 2.1

Trial replicate 2.1 represents the first of two field surveys to Vischgat on the Vaal River. Again, site conditions did not allow for the channel to be placed directly into the water and so fish had to be collected from the river and placed into a recirculating system. Fish were again allowed approximately 60 minutes to acclimate to the conditions within the experimental system prior to starting the first trial replicate. The results of the experimental replicate, together with the channel gradients and associated hydraulic conditions are presented in Table 3-4. These results are graphically presented in Figure 3-12.

Figure 3-12: Results of trial replicate 2.1 at the Vaal River (Vischgat). Fish species abbreviations are given in Appendix B.

140 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

The experimental testing was done over multiple days, using fresh testing populations periodically throughout the testing in an effort to eliminate fatigue as a limiting factor. The first experiment made use of four species of fish that were collected from the river. At a channel gradient of 1:5.7 a relatively good success rate was achieved for all four species. This replicate made use of only adult fish, which may be a contributing factor to the improved success rates throughout the testing population. Labeo capensis had a success rate of nine out of the 12 test individuals (75%), L. aeneus showed a 91% success rate (10 out of the 11 individuals), A. sclateri had a 75% success rate (three out of the four individuals) and T. sparrmanii showed a 60% success rate (three out of the four individuals). This trial replicate made use of a wider diversity of fish species, incorporating a wider diversity of body forms and groups representing a greater diversity of swimming abilities. It is the first trial replicate to include A. sclateri, which is thought to be a relatively weaker-swimming species (Skelton, 2001).

New fish test specimens were utilised for the 1:6.9 trial replicate but only two species, namely L. aeneus and L. capensis, these were the only species collected. Only adult L. aeneus individuals (SL > 100 mm) were utilised for the testing as no juveniles were collected. A noteworthy result including the successful passing of L. capensis and L. aeneus individuals measuring 364 mm SL and 340 mm (465 mm TL), respectively. It is recommended when designing a vertical slot fishway that the pool length is three times the length of the largest expected fish that it should cater for (Bok et al., 2004). The length of an individual pool of the experimental channel was approximately 445 mm, which means that it theoretically only caters for fish measuring approximately 148 mm (TL). It can be seen by the size ranges provided in Table 3-4 that many of the fish within the test population exceed the recommended size range. This shows that this size recommendation is rather a guideline value and is not necessarily a limiting factor. It was shown, however, that individual fish as large as 364 mm (SL) are able to successfully negotiate the restrictive dimensions of the channel and the hydraulic conditions induced by a gradient of 1:6.9. A mixed test population of adult (SL > 100 mm) and juvenile (SL < 100 mm) L. capensis was also utilised for this experiment. Of the 14 total individuals used (10 adults and four juveniles), 11 (79%) were successful in negotiating the experimental fishway channel (three juveniles and eight adults). This shows that juveniles of species that are regarded as stronger swimming species from the system (i.e. L. capensis and L. 141 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY aeneus) are comparably capable of negotiating the hydraulic conditions imposed by the fishway.

3.4.2.1.3. Trial replicate 2.2

Trail replicate 2.2 represents the second of two field surveys to Vischgat on the Vaal River. Site conditions did not allow for the channel to be placed directly into the water and so fish had to be collected from the river and placed into a recirculating system. The results of the survey, together with the channel gradients and associated hydraulic conditions are presented in Table 3-4. These results are graphically presented in Figure 3-13.

Figure 3-13: Results of trial replicate 2.2 from the Vaal River at Vischgat. Fish species abbreviations are given in Appendix B.

Greater success in collections of a test population of fish meant that more comprehensive testing of the channel with a greater diversity of species was possible. This was largely due to the timing of the survey (mid-summer). Four different gradients of the channel were

142 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY tested, with the system circulating for a period of 60 minutes per gradient. Only adult fish were used for the experiments, excepting for four juvenile L. capensis.

From Figure 3-13 it can be seen that at a gradient of 1:4.2 (Vs = 1.412 m/s; DH = 0.119 m;

3 Pv = 414.8 watts/m ) lowered success rates of those species perceived to be regarded as weaker swimming species (A. sclateri and P. philander). All four of the juvenile L. capensis were able to successfully negotiate the channel at this gradient. After lowering the gradient to 1:7.5, 1:8.4 and 1:10.8, there was a general overall improvement in positive results. Anomalies in results remain, however. Tilapia sparrmanii showed an 80% success rate at a gradient of 1:4.2, which then improved to 100% at a gradient of 1:7.5, leading to the assumption that lowering of the gradient would improve the overall success rate of the test individuals for this species. When the gradient was lowered to 1:8.4 the success rate of this species dropped to 40%, and then picked up again to 68% when the gradient was further lowered to 1:10.8. This trend of erratic results was also noted for the majority of the other species, although an overall improvement of results was noted as the channel gradient was changed from 1:4.2 to 1:7.5. Two barb species from the system were utilised for the experiments, namely B. anoplus and B. paludinosus. Comparatively, it can be assumed that B. paludinosus would be a stronger swimming species than B. anoplus due to the greater rigidity of its fins (Skelton, 2001) and B. paludinosus is generally found along the edges of fast-flowing water, whereas B. anoplus is generally found in quiet sheltered waters, but remains associated with flowing areas (Skelton, 2001). The results of these two species indicate the inverse to be true. There are similar positive results for these two species at a gradient of 1:4.2 (57%), but as the gradient increases, B. anoplus consistently has greater positive results than those of B. paludinosus. Another species of fish perceived to be a weaker-swimming species from the system is P. philander. This species showed consistent improved positive results as the gradient of the channel was lowered toward 1:10.8, indicating that this species, although capable of negotiating the hydraulic conditions created by the channel at steeper gradients, it would benefit from lower (flatter) gradients.

3.4.2.2. Sabie River

Two field surveys were undertaken at the Sabie River. The first survey coincided with receding water levels of the river following a high rainfall event that had induced freshet 143 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY conditions. The results from the first survey are presented as trial replicates 1 and 2. The fish were observed to be undertaking positive migrations during this field survey and therefore it was an ideal time to test the experimental fishway channel. Site conditions also allowed for the channel to be placed directly into a pool at the downstream side of the weir which fish were utilising to try to gain access across the weir. Placing the fishway entrance into this pool allowed all these fish to continue with upstream migrations. The results thus gained are representative of a test population with a naturally-strong drive to undertake migrations and therefore the limitations of the laboratory testing of the channel in trying to artificially induce individuals to swim up the channel did not exist. These results are therefore thought to be a more realistic representation of the swimming abilities of the fish species and populations within the river system.

It should be noted that trial replicates at the Sabie River were undertaken for a shorter period than those undertaken at the Vaal River. The reason for this was that ambient and the associated water temperatures at the time of the surveys were relatively high, leading to oxygen depletion within the experimental system relatively quickly. Routine replenishment of water and active circulation of the water was therefore necessary to conserve the vigor of the test populations. It was noted that leaving the experimental system for an extended period without circulation resulted in morbidity of the fish, which would impact on the results.

3.4.2.2.1. Trial replicate 1A

During this trial replicate the model fishway entrance was placed directly into a pool at the bottom of the weir. The fishway channel was adjusted to a gradient of 1:5, with the entrance to the fishway facing upstream into the river. As no fish were initially captured for the experiments, capture stress was not a factor in determining swimming abilities of the fish. An initial test population was also not established through capturing, so proportions of entire test population to successful individuals could not be determined. Fish attempting to negotiate passage up the experimental channel was also entirely fortuitous. The fishway was tested at a gradient of 1:5 for the initial experiment. High ambient temperatures at the time of the survey meant that a high level of morbidity amongst the fish within the upper collection tank was noted soon after circulation ceased, which was presumably as a consequence of increased was temperature and associated lower

144 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY oxygen content. Successful individuals (positive results) were therefore reported on as relative abundance values due to high numbers of fish rather than risking high mortality rates to count and measure each individual.

Table 3-5 shows that eight species were able to successfully negotiate the fishway channel at a gradient of 1:5. Noteworthy results are the dominance of small-bodied species, namely C. swierstrai, B. trimaculatus and Barbus viviparus (Bowstripe barb), with the smallest recorded individuals measuring 30 mm, 30 mm and 32 mm (SL), respectively. The size of the successful fish ranged from 30 mm to 80 mm for C swierstrai and L. molybdinus, respectively. The most abundant species were C. swierstrai and L. molybdinus, with more than 100 individuals having been estimated to have successfully negotiated the fishway channel. Where large numbers of species were observed, numbers of individuals were estimated to avoid high fatalities. This was due to the rapid decline of the health status of the fish due to high ambient temperatures, necessitating rapid handling and processing of the fish. Labeo cylindricus juveniles also potentially utilised the fishway during this experiment. Identification of juveniles to discern the differences between L. cylindricus and L. molybdinus was not possible under field conditions where speedy handling of the fish was required to avoid high mortality rates.

Table 3-5: Fish species that successfully negotiate up the vertical slot type fishway at the given gradients during experiments at the Sabie River for the first of the two field surveys. The standard lengths (SL) (mm) ranges are given in brackets. A summary of the hydraulic conditions is also provided.

Trial replicates Trial replicate 1A Trial replicate 1B Trial replicate 2 M=1:5 M=1:4 M=1:3.15 Vs=1.401 Vs=1.412 Vs=1.412 Channel conditions DH=0.100 DH=0.125 DH=0.159 Pv=338.8 Pv=441.1 Pv=603.4 SF=Yes SF=No SF=No CSWI (30-38) RA=5 CSWI (35-40) RA=4 Fish individuals, LMOL (42-80) RA= 5 BVIV (40-50) RA=4 BTRI (50-55) RA=1 numbers and size BUNI (41-70) RA=4 BTRI (50-70) RA=4 BRAD (50) RA=1 ranges that BVIV (32-50) RA=4 CSWI (30-50) RA=5 LMOL (70-100) RA=2 successfully BMAR (60) RA=1 LMOL (50-80) RA=5 OPER (45-60) RA=0 negotiated the fishway OPER (45-55) RA=2 OPER (50-70) RA=2 MACU (50-70) RA=0 channel BTRI (30-60) RA=4 MBRE (30-50) RA=0 BRAD (55-60) RA=1 Relative abundance (RA): 0-absent; 1-rare (1-2); 2-moderate (3-6); 3 common (7-10); 4-abundant (11-50); 5-very abundant (>50). M=Channel gradient; Vs=Water velocity through slot (m/s); DH=Change in water level from one pool to the next (m); 3 Pv=Turbulence (watts/m ); SF=Submerged flow conditions (yes/no). Fish species abbreviations are given in Appendix B.

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3.4.2.2.2. Trial replicate 1B

The model fishway entrance was placed directly into a pool at the bottom of the weir. The fishway was tested at a gradient of 1:4 for 50 minutes. Five fish species managed to negotiate the model vertical slot fishway successfully at a gradient of 1:4 (Table 3-5). The smallest individuals able to negotiate the fishway during this setup were C. swierstrai, measuring 30 mm. The largest individuals in the fishway were L. molybdinus individuals with a SL of 80 mm. Two species, namely C. swierstrai and L. molybdinus were noted to be particularly abundant in the river system at the time of the survey.

3.4.2.2.3. Trial replicate 2

The model fishway entrance was placed in a secondary channel of the main watercourse approximately 30 m downstream of the weir, with the entrance facing downstream in the river. The system was circulated again, with the gradient of the fishway channel adjusted to 1:3.15 for a period of 60 min. Three species from the river channel managed to find the entrance and successfully negotiate, namely C. swierstrai, B. trimaculatus and Barbus radiatus (Beira barb) (Table 3-5). The smallest individual successfully negotiating this experimental setup were those of C. swierstrai, measuring 35 mm (SL). Further to this, fish were collected from below the weir and placed into the bottom pool of the fishway of the fishway while a net was placed at the entrance so the fish could not escape. The fishway was run at a gradient of 1:3.15. Five species managed to negotiate the fishway successfully after a period of 20 min. The smallest individuals capable of negotiating the fishway at this again was C. swierstrai with a SL of 35 mm. The largest individual successfully negotiating the fishway at this setup was L. molybdinus individuals with a SL of 100 mm. Three species, namely Opsaridium peringueyi (Southern barred minnow), M. brevianalis and Micralestes acutidens (Silver robber) placed in the last pool of the fishway channel did not reach the top bucket at this gradient. As no attempts to negotiate the channel were noted for individuals of these species, it is uncertain whether attempts to negotiate the fishway were made. Fouche & Heath (2013) noted M. acutidens to be a strong migratory species and therefore they may have still been susceptible to capture and handling stress as well as the stress induced from being confined within an artificial system and therefore were reluctant to attempt the channel. These three species are also known to be particularly dependent on high oxygen content within the water and would be

146 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY affected by the oxygen depletion that occurred within the experimental system due to high ambient temperatures and resultant increasing water temperature.

3.4.2.2.4. Trial replicate 3

Trial replicate 3 to trial replicate 6 were undertaken during the second of the two field surveys at the Sabie River within the Kruger National Park. All of these experiments made use of captured fish from the river system and running the fishway channel as a closed recirculation system. All trial replicates were undertaken twice. The first trial replicate ran for a duration of 50 minutes, with the fish placed within the bottom collection tank. It was found as a general result of this that relatively few fish attempted upstream passage through the channel. An attempt to improve the results was made by confining the fish to the last pool of the fishway. The resulting crowded conditions tended to induce an escape response and, in this way, more fish attempted upstream passage. The overcrowding created stress within the fish and therefore this part of the trial replicate was limited to a duration of 20 minutes. Table 3-6 presents the results of the series of trial replicates, together with a summary of the hydraulic conditions.

Trial replicate 3 made use of a fish test population, the details of which are indicated in Table 3-6 and graphically presented in Figure 3-14. A gradient of 1:5.7 was used for this experiment. Of the 15 species utilised for the experiment, only individuals of eight species successfully negotiated the fishway channel. Clarias gariepinus showed the greatest proportional success rate at 100% of the test populations, but it should be noted, however, that only one individual was used for the experiment. Similarly, 50% of the test population of two individuals of B. viviparus was also successful in negotiating the channel. Labeobarbus marequensis showed the most noteworthy success rate, with 73.3% of the test population (45 individuals) being successful. Other species that successfully negotiated the channel at this gradient included C. swierstrai (2.2%), B. trimaculatus (14.3%), L. molybdinus (19.2%), M. acutidens (33.3%) and B. imberi (60%). It can be seen from Figure 3-14 that almost half of the species used for the trial replicate did not have any individuals that successfully negotiated the channel. These included B. radiatus, O. peringueyi, P. philander, O. mossambicus, Tilapia rendalli (Redbreast tilapia), C. paratus and C. anoterus.

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Trial replicate Trail replicate Trial replicate Trial replicate Trial replicate 5 Trial replicate 6 3 4A 4B M=1:5.7 M=1:3.6 M=1:3.6 M=1:7.7 M=1:11 Vs=1.314 Vs=1.412 Vs=1.412 Vs=1.129 Vs=0.940 Channel DH=0.088 DH=0.139 DH=0.139 DH=0.065 DH=0.045 conditions Pv=270.5 Pv=505.1 Pv=505.1 Pv=162.3 Pv=89.9 SF=Yes SF=No SF=No SF=Yes SF=Yes Duration 50+20 mins 50+20 mins 50+20 mins 50+20 mins 50+20 mins BMAR (38-200) BMAR (38-200) (No=45; Ns=33) (No=45; Ns=23) CSWI (40-60) CSWI (40-60) BMAR (55-250) BMAR (55-250) (No=45; Ns=1) (No=45; Ns=3) (No=61; Ns=14) (No=61; Ns=20) BTRI (40-70) BTRI (40-70) MACU (50-70) MACU (50-70) (No=7; Ns=1) (No=7; Ns=0) (No=74; Ns=1) (No=74; Ns=4 CGAR (190) CGAR (190) BVIV (45-50) BVIV (45-50) (No=1; Ns=1) (No=1; Ns=0) (No=4; Ns=0) (No=4; Ns=0) LMOL (60-220) LMOL (60-220) PPHI (40-60) PPHI (40-60) (No=26; Ns=5) (No=26; Ns=8) (No=8; Ns=0) (No=8; Ns=0) MACU (50-70) MACU (50-70) OMOS (35-70) OMOS (35-70) OMOS (175-190) Fish (No=6; Ns=2) (No=6; Ns=1) (No=18; Ns=0) (No=18; Ns=0) (No=6; Ns=2) individuals, BVIV (50) BVIV (50) BTRI (40-70) BTRI (40-70) BIMB (130) numbers and (No=2; Ns=1) (No=2; Ns=0) (No=3; Ns=0) (No=3; Ns=1) (No=1; Ns=0) size ranges BRAD (65-70) BRAD (65-70) TREN (40-130) TREN (40-130) BVIV (30) that (No=4; Ns=0) (No=4; Ns=0) (No=19; Ns=1) (No=19; Ns=7) (No=3; Ns=0) successfully OPER (50) OPER (50) CSWI (40-60) CSWI (40-60) TREN (95-175) negotiated (No=2; Ns=0) (No=2; Ns=0) (No=6; Ns=0) (No=6; Ns=0) (No=5; Ns=2) the fishway PPHI (20-60) PPHI (20-60) LMOL (55-300) LMOL (55-300) HVIT (160) channel (No=9; Ns=0) (No=9; Ns=0) (No=26; Ns=9) (No=26; Ns=13) (No=1; Ns=1) OMOS (30) OMOS (30) OPER (50) OPER (50) (No=5; Ns=0) (No=5; Ns=0) (No=2; Ns=0) (No=2; Ns=0) TREN (60) TREN (60) CPAR (55-60) CPAR (55-60) (No=2; Ns=0) (No=2; Ns=0) (No=2; Ns=0) (No=2; Ns=0) CPAR (40-55) CPAR (40-55) CANO (55-60) CANO (55-60) (No=2; Ns=0) (No=2; Ns=1) (No=5; Ns=1) (No=5; Ns=2) CANO (40-65) CANO (40-65) MMAC (120-165) MMAC (120-165) (No=5; Ns=0) (No=5; Ns=0) (No=3; Ns=2) (No=3; Ns=0) BIMB (135) BIMB (135) (No=5; Ns=3) (No=5; Ns=0)

M=Channel gradient; Vs=Water velocity through slot (m/s); DH=Change in water level from one pool to the next (m); 3 Pv=Turbulence (watts/m ); SF=Submerged flow conditions (yes/no). No=number of individuals of each species used for each experiment; Ns=number of successful individuals per experiment. Fish species abbreviations are given in Appendix B.

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Figure 3-14: Results of trial replicate 3, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B.

3.4.2.2.5. Trial replicate 4

Trial replicate 4 was undertaken in two parts (4A and 4B). Both trial replicates were undertaken with the fishway channel set at a gradient of 1:3.6, but a new test population was captured and utilised for trial replicate 4B. The same test population of fish was utilised for trial replicate 4A as were used for trial replicate 3. The same trial procedures were followed as for all of the field trial replicates at this site, namely circulation of the experimental system for 50 minutes with the fish population in the bottom tank, and then a further 20 minutes with the fish placed in the first pool of the channel. The results are presented in Figure 3-15.

When compared to the results following trial replicate 3, it can be seen that overall, fewer species negotiated the channel when the gradient was increased from 1:5.7 (from trial replicate 3) to 1:3.6. With the increased gradient of the channel, a greater diversity of 149 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

Chiloglanis species and individuals negotiated the channel. This indicated that channel turbulence and water velocities induced by the steeper gradient does not necessarily impede the swimming abilities of these species. This was also true for L. molybdinus, where comparably more individuals successfully negotiated the channel at the steeper gradient. Species regarded as strong swimmers (L. marequensis) showed a decline in positive results, which could indicate a limitation to the hydraulic characteristics of the channel, to this species. There were a lack of positive results for small Barbus species and Brycinus imberi (Imberi) at this gradient.

Figure 3-15: Results of trial replicate 4A, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B.

The same channel gradient was utilised for a repeat of the trial replicate, but a new test population was captured from the river and utilised for trial replicate 4B. The results are presented in Figure 3-16. When comparing the results of the two experiments as a percentage of positive results of the test population by species, an overall decline in positive results of L. marequensis (51.1% to 22.0%) was noted. 150 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

Figure 3-16: Results of trial replicate 4B, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B.

Similarly, declining results were noted for M. acutidens (16.7% to 1.4%), C. swierstrai (6.7% to 0%) and C. paratus (50% to 0%). Improved positive results were noted for T. rendalli (0% to 5.3%), L. molybdinus (30.8% to 34.6%) and C. anoterus (0% to 20%). Individuals of all of these species have been shown to successfully negotiate the channel at a steeper gradient (1:3.15) and therefore the relatively low numbers of positive results may be attributed to a lack of attempts by the fish to negotiate the channel rather than hydraulic limitations. A noteworthy result came from Marcusenius macrolepidotus (Bulldog), which is a species that had not yet been utilised for any trial replicates. Three individuals were captured from the river and placed in the system. Two of the three (66%) of the individuals were able to successfully negotiate the channel at the gradient of 1:3.6. This species inhabits well-vegetated, quiet backwaters of systems and shows a preference for mud substrates (Skelton, 2001). This habitat preference, and the body and fin structure of this species all imply that this is a weak swimming species that cannot negotiate turbulence. Positive results for negotiating the fishway channel indicate that this 151 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY species can indeed negotiate relatively high turbulence levels. This species is regarded as the weakest swimming species of all of the species utilised for the trial replicates using the vertical slot fishway and therefore positive results are an indication of the effectiveness of the channel design in mitigating riverine habitat fragmentation. As far as could be ascertained, these data are novel for this species, with no records of any species of the family of Mormyridae having successfully negotiated a fishway. These results, again, reiterate the nature of the experimental design that relies on a swimming response of the fish and the inconsistent responses of the individual fish.

3.4.2.2.6. Trial replicate 5

A new test population of fish was captured and utilised for trial replicate 4B and these same individuals were utilised for trial replicate 5. The fishway channel was set at a flatter gradient (1:7.7) for this trial as opposed to 1:3.6 that was used for trial replicate 4B. Six fish species successfully negotiated the entire length of the channel (one more species than for trial replicate 4B, namely B. trimaculatus). Previous results have indicated that this species could successfully negotiate the channel at steeper gradients. These results are presented in Figure 3-17.

Overall, more individuals successfully negotiated the channel at the lower gradient than were successful in negotiating the channel at a gradient of 1:3.6, indicating that the hydraulic characteristics associated with a channel gradient of 1:3.6 were a limiting factor to the fish. This was most noteworthy in the test population of T. rendalli and is therefore considered to be relevant to deeper-bodied (compressiform) species (e.g. Cichlidae). It should also be considered, however, that the test population was provided with a greater time to acclimatise to the test conditions and therefore were more inclined to attempt swimming through the channel. Included in the positive results of this experiment was the successful negotiation of a L. molybdinus individual through the channel that measured 330 mm (SL). This individual is approximately twice the length of the theoretical maximum length of fish that the channel was designed to cater for, reiterating that the channel of these dimensions can indeed cater for larger fish species if required. The M. macrolepidotus individuals that were successful in negotiating the steeper gradient of 1:3.6 (trial replicate 4B) were not successful in negotiating the channel at a gradient of 1:7.7. It is assumed that this was through a lack of attempting to negotiate the channel rather than

152 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY the hydraulic characteristics being a limiting factor, although fatigue may have been a contributing factor.

Figure 3-17: Results of trial replicate 5, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B.

3.4.2.2.7. Trial replicate 6

A new test population of fish was captured and utilised for this trial replicate. Details of the test population are presented in Table 3-6. The channel was set at a gradient of 1:11. A similar test protocol was followed, where the fish were placed in the bottom tank and the system circulated for 50 minutes. Again, relatively poor results were obtained, with only one O. mossambicus and one T. rendalli successfully negotiating the channel. These results are presented in Figure 3-18. After crowding the fish in the last pool of the fishway channel, the system was circulated for a further 20 minutes.

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Figure 3-18: Results of trial replicate 6, showing the percentage success rates of the test populations of the individual species at the given channel gradient. Fish species abbreviations are given in Appendix B.

Results were relatively better following procedure, with more fish (of the same species) seen attempting to swim up the channel. This result is consistent with those of the previous trial replicates that utilised a similar protocol. The most noteworthy result of this experiment was the successful negotiation of the channel by H. vittatus, which is a species that had not been utilised or any trial replicates before. This species is, however, regarded as a strong migratory species which inhabits fast-flowing water (Skelton, 2001), meaning that this species is able to maintain position in highly-turbulent habitat types and to utilise strong water currents to its advantage. This presupposes that this species would be able to negotiate the fishway channel at relatively steeper gradients. This species succumbs to stress and deteriorating water quality relatively quickly (Gagiano, 1997) and therefore testing within a recirculating field system is not regarded as ideal. No opportunity was afforded to test the swimming abilities of this species at steeper gradients due to it only being collected at the end of the survey. The experiment at the relatively flatter gradient of 1:11 induces lower turbulence within the pools and water velocities through the slots

154 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY between the pools. The lack of attraction flows may therefore have been a factor in the fish not being induced to undertake upstream passage through the channel.

3.4.3. Summary of field survey results

A summary of all of the field survey data per species is presented in Figure 3-19 as a percentage success rate of the test population of each individual species (A to X) to successfully negotiate the fishway channel at the given gradients. Only the channel gradients applicable to the fish species are included.

A B

C D

155 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

E F

G H

I J

K L K K 156 | P a g e

CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

M N

O P

Q R

S T

157 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY

U V

W X

Figure 3-19: Summary of the field tests of the experimental vertical slot fishway for each individual species for both the Vaal River and Sabie River field surveys. Only the gradients applicable to the species tested for are indicated. Fish species abbreviations are given in Appendix B.

Table 3-7 presents a summary of the data presented in Figure 3-19, where the most successful gradient to be negotiated by the various fish species, the percentage of the test population of the species that were able to successfully negotiate this channel gradient and the hydraulic parameters applicable to the gradient are shown. A determination if the results gained through the field testing per species are conclusive is provided. Only data from test replicates that provided to a success rate of greater or equal 70% of the test population of species are considered conclusive. Confidence limits in the results are also included, which are based on grading the interpretation of the data that were assumed to be anomalous. The confidence limit of the results also plays a role in determining if the data can be considered conclusive. A species such as H. vittatus that is regarded as a strong swimming and powerful species was shown to successfully negotiate the channel at a relatively flat gradient of 1:11. Only one individual was also available for the trial testing,

158 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY and only one opportunity was afforded during the field surveys to incorporate this species. It is assumed that this species is able to negotiate relatively steeper gradients and that the reporting of 1:11 being an upper limit of the gradients that this species could negotiate is not thought accurate. Therefore this species is reported on with a low (1) confidence. The results for B. radiatus, B. imberi and O. mossambicus also were given a low confidence limit for similar reasoning. The results for M. macrolepidotus are provided with a lower confidence limit due to the general lack of data pertaining to the swimming abilities of this species. These results also provide novel data for this species and therefore more testing would be required in order to increase the confidence limits of the data.

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Table 3-7: Summary of the channel gradients successfully negotiated by the fish species and the associated hydraulic conditions.

Hydraulic parameters Steepest gradient Hydraulic parameters Most successful successfully gradient negotiated. Is data Species Conf* negotiated. (% test (% test population Vs DH Pv conclusive? Vs DH Pv 3 population to 3 to negotiate this) (m/s) (m) (watts/m ) (m/s) (m) (watts/m ) negotiate this) BMAR 1:5.7 (73%) 1.33 0.09 270.5 Yes 5 1:3.6 (51%) 1.66 0.14 505.1 BAEN 1:7 (100%) 1.17 0.07 212.5 Yes 5 1:3.8 (57%) 1.60 0.13 472.7 LCAP 1:8.4 (90%) 1.09 0.06 142.5 Yes 5 1:4.2 (73%) 1.53 0.12 414.8 LMOL 1:5 (90%) 1.40 0.10 338.8 Yes 5 1:3.15 (30%) 1.77 0.16 603.4 BANO 1:10.8 (86%) 0.95 0.05 93.10 Yes 5 1:4.2 (71%) 1.53 0.12 414.8 BPAU 1:5 (50%) 1.40 0.10 338.8 No 3 1:4.2 (43%) 1.53 0.12 414.8 BRAD 1:5 (10%) 1.40 0.10 338.8 No 1 1:3.15 (10%) 1.77 0.16 603.4 BTRI 1:5 (75%) 1.40 0.10 338.8 Yes 5 1:3.15 (10%) 1.77 0.16 603.4 BUNI 1:5 (75%) 1.40 0.10 338.8 Yes 5 1:5 (75%) 1.40 0.10 338.8 BVIV 1:5 (75%) 1.40 0.10 338.8 Yes 5 1:4 (75%) 1.60 0.13 441.1 OPER 1:5 (30%) 1.40 0.10 338.8 No 3 1:4 (30%) 1.60 0.13 441.1 CANO 1:7.7 (40%) 1.13 0.07 162.3 No 3 1:3.6 (20%) 1.66 0.14 505.1 CPAR 1:3.6 (50%) 1.66 0.14 505.1 No 3 1:3.6 (50%) 1.66 0.14 505.1 CSWI 1:5 (90%) 1.40 0.10 338.8 Yes 5 1:3.15 (75%) 1.77 0.16 603.4 CGAR 1:8.4 (100%) 1.09 0.06 142.5 Yes 5 1:5.7 (100%) 1.33 0.09 270.5 ASCL 1:10.8 (90%) 0.95 0.05 93.10 Yes 5 1:4.2 (33%) 1.53 0.12 414.8 TSPA 1:7.5 (100%) 1.15 0.07 170.6 Yes 5 1:4.2 (80%) 1.53 0.12 414.8 TREN 1:11 (40%) 0.99 0.05 89.9 No 3 1:3.6 (55%) 1.66 0.14 505.1 OMOS 1:11 (33%) 0.99 0.05 89.9 No 1 1:11 (33%) 0.99 0.05 89.9 PPHI 1:10.8 (67%) 0.95 0.05 93.1 No 3 1:4.2 (33%) 1.53 0.12 414.8 HVIT 1:11 (100%) 0.99 0.05 89.9 Yes 1 1:11 (100%) 0.99 0.05 89.9 MACU 1:5.7 (33%) 1.33 0.09 270.5 No 3 1:3.6 (17%) 1.77 0.16 505.1 BIMB 1:5.7 (60%) 1.33 0.09 270.5 No 3 1:5.7 (60%) 1.33 0.09 270.5 MMAC 1:3.6 (66%) 1.66 0.14 505.1 No 3 1:3.6 (66%) 1.66 0.14 505.1

Vs=Water velocity through the slot between pools; DH=Change in water height between two successive pools; Pv=Average turbulence levels within each pool. *Confidence: 1-Low confidence; 3-Medium confidence; 5-High confidence. Fish species abbreviations are given in Appendix B.

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Figure 3-20 presents a summary of the gradients that were most successful for each fish species utilised for the trial replicates. The percentage of the test population per species is provided that displayed for the gradient that showed the greatest success rate. The gradient of the channel is provided as a percentage slope. The limit to consider a fishway ecological successful is set at equal or greater than 70% success rate for a particular fish species. This is indicated in Figure 3-12 as the red horizontal line. The trial replicates that could not be considered to offer conclusive results can be clearly distinguished when the data are presented in this format.

Figure 3-20: Summary of the data collected from trial testing of the vertical slot fishway under field conditions, showing the channel gradients that showed the most success rates and the percentage of the test population of each species that successfully negotiated the channel at the given gradient. A limit of 70% of the test population to successfully negotiate the channel is thought to be the limit in considering if the data are conclusive. Fish species abbreviations are given in Appendix B.

From Figure 3-20, it can be deduced that the most favourable results were achieved at gradients between 10% (1:10) and 20% (1:5) and that gradients less than 10% (1:10) did not yield more favourable results. The gradient of the fishway is presented as a percentage slope for presentation purposes. The channel gradients (as presented

161 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY throughout the thesis) and how they translate to percentage slope are indicated in Table 3- 8.

Table 3-8: Fishway channel gradient and how it translates to percentage slope.

Gradient % Slope Gradient % Slope 1:3.15 31.7 1:6.90 14.5 1:3.60 27.8 1:7.00 14.3 1:3.80 26.3 1:7.50 13.3 1:4.00 25.0 1:7.70 13.0 1:4.20 23.8 1:8.40 11.9 1:4.90 20.4 1:10.0 10.0 1:5.00 20.0 1:10.8 9.26 1:5.70 17.5 1:11.0 9.09

3.4.4. General observations and other applicable information

3.4.4.1. Migratory cues, timing and reasons for migrations

Active migration activity by the fish communities was noted during the first of the field surveys at the Sabie River undertaken during mid-November. Extensive rains fell in the catchment in the period preceding the field survey (pers. comm. 5Deacon, 2004), after which the river flow rate, as measured by the DWS gauging weir at the survey site, increased from 3 m3/s to 8 m3/s (Figure 3-21). The survey was undertaken during the receding period following the peak flow of 8 m3/s (indicated in Figure 3-21).

The increased flows experienced within the river coupled to the recent rainfall was the only major environmental event prior to activation of the migratory activity within the fish communities. It can therefore be assumed that the increased flow volume of the watercourse (and the expected associated environmental changes such as increased habitat availability, increased nutrient loads, changes in physico-chemical properties of the water, turbulence, drowning out of small migratory barriers and possibly also temperature changes) is what induced the migratory activity of the fish communities. Both adult and juvenile fish were observed to be actively migrating, which shows that the reasons for the

5 Dr Andrew Deacon, Research Scientist, Skukuza, Kruger National Park, Nov. 2004.

162 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY migratory activity were for spawning as well as for general exploitation of new habitat (for feeding, general dispersal and opportunistic exploitation of resources). These deductions were all based on general observations and therefore do not have high confidence limits.

Figure 3-21: Flows measured at the Kruger Gate Weir (X3H021) for the Sabie River for the time preceding the time of the first field survey (indicated by the arrow) as well as immediately afterwards (taken from DWAF, 2005).

Fish were also showing strong migratory behaviour during field surveys to the Vaal River. Adult L. capensis and L. aeneus were actively jumping into the white waters flowing over a weir (Figure 3-22). Observations showed that this migratory behaviour activity seemed to reach a peak from late afternoon (approximately 16h00) and continue until dusk, after which further observations were not possible. This was observed during all consecutive days of the survey. Only very few of the fish observed jumping were actually successful at negotiating the weir. This was observed to be due to the presence of a flat steel plate placed vertically on the rim of the weir, which is typical of this type of weir, being a sharp- crest weir (Rossouw et al., 1995).

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Figure 3-22: Labeo capensis adults attempting to negotiate upstream across the weir.

3.4.4.2. Migratory behaviour, swimming and jumping behaviour

The timing of the first of the field surveys to the Sabie River coordinated with a phase of active migrations as it was timed to coincide with a major rainfall event within the catchment area. This meant that visual observations were made of migratory behaviour that were not necessarily applicable to the actual trial replicate procedures but remain noteworthy in terms of migratory potential. It is these observations that allow for refinements of the confidence limits that were applicable to the replicate trials during the formal testing of the fishway channel. Other visual observations for fish during the field surveys applicable to fish migration potential were also noted during all the surveys. The information gathered during these observations is useful when designing a fishway and setting the limits of the hydraulic parameters of that fishway. Table 3-9 presents a summary of the species accounts for these observations.

Table 3-9: Summary of the visual observations at the time of the field survey.

Estimated Species size range Comments (SL – mm) Large numbers of juveniles negotiated the weir successfully by adhering to the Labeo 40 – 100 wetted surface at the periphery of the flow (Figure 3-23). Using a crawling and molybdinus sucking mechanism they were able to successfully overcome the weir. This species was sampled below weir within the main stream of the watercourse where turbulence was considered to be the greatest. Individuals were observed Labeo rosae 250 – 350 jumping into white water that flowed over the weir, which were presumed unsuccessful. No individuals were observed within the side channels of the river, implying that they seek the highly turbulent flow conditions.

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Estimated Species size range Comments (SL – mm) Observed jumping within the white waters below the weir and being swept back down by the current. These attempts were presumed unsuccessful. Individuals Clarias 500 – 700 were also observed within the side channels where less turbulence was gariepinus encountered. This species was also successful in negotiating the experimental fishway channel (although limited to only one test individual). Micralestes Observed in large numbers directly below weir, indicating that it is a species that 50 – 80 acutidens undergoes active migrations. Barbus 30 – 70 trimaculatus Observed in large numbers directly below weir, indicating that these species Barbus 32 – 50 undergo active migrations. Individuals were observed jumping clear over a 300 viviparus mm vertical surface (a small concrete weir constructed within a side channel). Barbus 41 – 70 unitaeniatus Barbus Observed in large numbers directly below weir, indicating that it is a species that 55 – 60 radiatus undergoes active migrations. Opsaridium Observed in large numbers directly below weir, indicating that it is a species that 45 – 60 peringueyi undergoes active migrations. Observed in large numbers directly below weir, indicating that it is a species that Chiloglanis undergoes active migrations. Individuals observed using specialised sucker-like 30 – 38 swierstrai mouthparts to adhere to wetted surfaces. Were able to negotiate vertical surface successfully in this way (Figure 3-24). Mesobola Observed in large numbers directly below weir, indicating that it is a species that 50 – 70 brevianalis undergoes active migrations.

Large numbers of fish were noted to be undertaking active migrations at the time of the first field survey to the Sabie River. Figure 3-25 shows how fish opportunistically would utilise the wetted surfaces along the periphery of the main flow to gain access across the weir (Kruger Gate Weir). Observations of fish successfully negotiating extremes in hydraulic conditions such as this can also be applied when considering the confidence limits of the formal experimental data.

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Figure 3-23: Labeo molybdinus successfully negotiating a small vertical wall below the weir, as referred to in Table 3-8.

Figure 3-24: Chiloglanis swierstrai individuals observed negotiating vertical concrete wall at the base of a weir. Individuals were observed to often negotiate passage on the periphery of the flowing areas as referred to in Table 3-8.

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Figure 3-25: Fish congregating along the wetted periphery of the watercourse as it flowed over the weir as they attempt to negotiate passage across the weir. Labeobarbus molybdinus, B. viviparus and B. trimaculatus dominated the species composition here.

3.4.4.3. Age class of migratory fish

It was observed that the fish actively migrating included both juvenile and adult individuals of most species and that the majority of the larger-bodied fish species sampled were considered juveniles (especially L. molybdinus and L. marequensis). Only adults of C. gariepinus and L. rosae were observed migrating. All L. molybdinus individuals were juveniles ranging between 42 mm and 100 mm (SL). The experiments were undertaken within side channels of the main watercourse and therefore outside of the fast-flowing and turbulent areas. Collection of fish was also undertaken where habitat and flow-depth classes allowed for electronarcosis, which requires wadeable depth water that is easily and safely negotiated by the operator. It is therefore assumed that the lack of adult individuals of the larger-bodied species was due to locality of the collections and

167 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY experiments rather than it being considered that there was a lack of adult size ranges within the migrating fish at the time of the surveys and experiments.

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3.5. CONCLUSIONS & RECOMMENDATIONS

The aim of this chapter was to validate data that were gathered from the laboratory testing of the experimental fishway channel (Chapter 2) under actual field conditions using fish that were undergoing active migrations. The data thus gathered expanded on the knowledge base of the migrational behaviour and swimming potential of a greater diversity of fish species. The laboratory testing of the experimental fishway channel utilised three gradients, namely 1:3, 1:4 and 1:5 under varying flow conditions. This chapter included the testing of 16 channel gradients and expanded the knowledge base of species from five (Chapter 2) to a further 19 species that were not utilised during the laboratory tests. Further data were also generated for the five species that were used for the laboratory testing, which enabled validation of the data gathered in Chapter 2.

As mentioned previously, the results of the field trial testing relied on the will of the fish to attempt to swim up the channel. Determining whether the limiting factor to the successful negotiation of the channel was the hydraulic conditions at a given gradient or merely a lack of willingness of the fish individuals to attempt passage proved to be a general limitation to the field trial testing of the channel, as it was to the laboratory testing. The resulting data are therefore open to speculation and their ecological relevance are subject to confidence limits.

Fish are known to actively migrate during periods when rivers are experiencing flooding conditions, or when flow volumes are subsiding following a flood event. This implies that the river is subject to more difficult hydraulic conditions to negotiate, and it may be the

169 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY increase in turbulence and water velocities that actually trigger the migratory response. A lower gradient of a fishway channel lowers the hydraulic parameters whereas the steeper the gradient, the more extreme the hydraulic conditions within the channel become. For fish to actively find the entrance to a fishway, sufficient attraction flows are required (Bok et al., 2007), which is an area at the entrance of a fishway that experiences relatively greater turbulence than the local river area to attract the fish toward the current that exits the fishway. This implies that fish actively seek out stronger currents within a river to follow upstream during active migratory periods. These data potentially indicate that a fishway channel with a too low a gradient and too gentle hydraulic parameters would not be utilised by a wide diversity of fish species and therefore not be considered ecologically functional. This therefore shows that determining the lower hydraulic limits that would stimulate the fish to utilise the fishway channel are as important as discerning the upper limits to the hydraulic parameters that the fish can successfully negotiate.

Capture stress and the stress associated with the lack of acclimation to the holding system was a considerable factor throughout the field testing that negatively affected the overall results. The positive results gathered are an indication of the abilities of the swimming abilities of the fish. The negative results, where no individuals successfully negotiated the channel at a given gradient, are not thought to be an absolute indication of the swimming abilities of the fish. The experimental procedures relied exclusively on inducing the fish to actually attempt upstream passage through the channel and results were hindered by the lack of attempts. Data were therefore seen to be erratic, with zero individuals attempting passage at a relatively flat gradient, which would indicate negative results, but the same individuals would negotiate a channel at a steeper gradient. It is given that these individuals would be able to successfully negotiate the channel at the flatter gradients and therefore their lack of attempting cannot be regarded as a lack of ability to negotiate it. This concept was reiterated by the general observations of various fish species undertaken during the field surveys that were undergoing active migrations that showed the extraordinary abilities of various species to overcome instream barriers. Chiloglanis swierstrai showed the ability to negotiate vertical surfaces by adhering to the wetted surface with their sucker-like mouthparts and progressing steadily forwards through a series of swimming and sucking movements and actions. The morphology of these species indicate that they are highly adapted to inhabiting areas that experience high turbulence and water velocities. Facing into the current, the water flow over their heads

170 | P a g e CHAPTER 3: FIELD TRIALS OF EXPERIMENTAL IN SITU FISHWAY creates downward pressure to the surface, aiding in allowing the fish to maintain its position in strong currents. Juvenile L. molybdinus were also shown to be able to negotiate the same vertical surface in much the same way, but tended to utilise swimming motions comparatively more than C. swierstrai. This observation shows that it may be useful to ensure a roughened concrete surface is utilised when constructing a fishway. A roughened surface would also presumably enhance movement of aquatic macro- invertebrates through the fishway.

Bok et al. (2007) recommended that hydraulic parameters for relatively small fish not exceed turbulence levels of 150 watts/m3, change in water levels of 100 mm and water velocities through the slots of 1.4 m/s. Internationally, according to Larinier (2000), the recommended upper limit for turbulence for adult salmonid species (which have a swimming potential comparable to the generally stronger-swimming species from South African river systems) is 200 watts/m3, with the upper limits for juvenile salmonid and other weaker swimming species being recommended at 150 watts/m3. The results from the field experiments showed individuals of these two species (C. swierstrai and L. molybdinus) successfully negotiating turbulence levels 505.1 watts/m3 (Table 3-7), change in water levels of 139 mm and water velocities of 1.412 m/s indicating that these species can accommodate hydraulic parameters greater than the recommended national and international limits. It should be noted, however, that the experimental channel was relatively short and only managed an overall height difference of 0.8 m at a slope of 1:5 (20%), with eight slots over a channel length of 4.8 m. The experimental fish were therefore required to negotiate the hydraulic conditions within the experimental channel for only a short period of time. Migratory barriers that require fishways are considerably higher than this and therefore will be exposed to the hydraulic conditions for a longer period of time (often requiring 20 to 25 pools). It is therefore recommended when designing a fishway that the maximum hydraulic parameters stay well within the capabilities of the weakest swimming species in order to prevent excessive fatigue and energy expenditure. With this in mind, and from the data gained through the field trial replicates, it is recommended that fishways that are longer than 10 pools long do not exceed a channel gradient of 1:10.

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3.6. REFERENCES

Bartson, A. P. (1997). Smith River Fisheries and Ecosystem Report. Institute for River Ecosystems. Humboldt State University, Arcata California, United States. Accessed October 2010 at URL: http://www.reocities.com/rainforest/3771/index.html. Baumgartner, L., Zampatti, B., Jones, M., Stuart, I. and Mallen-Cooper, M. (2014). Fish passage in the Murray-Darling Basin, Australia: not just an upstream battle. Ecological Management and Restoration Volume 15 No. S1 March 2014. Ecological Society of Australia and Wiley Publishing Asia (Pty) Ltd. pp 28-39. Bok, A.H., Rossouw, J. and Rooseboom, A. (2004). Guidelines for the planning, design and operation of fishways in South Africa. WRC Report No. 1270/2/04. Water Research Commission, Pretoria, South Africa. p. 87. Bok, A., Kotze, P., Heath, R. and Rossouw, J. (2007). Guidelines for the planning, design and operation of fishways in South Africa. WRC Report No. TT 287/07. Water Research Commission, Pretoria, South Africa. Booth, R.K., McKinley, R.S., Økland, F. and Sisak, M.M. (1997). In situ measurement of swimming performance of wild Atlantic salmon (Salmo salar) using radio transmitted electromyogram signals. Aquatic Living Resources, 10: 213-219. Bunt, C.M. (2001). Fishways entrance modification enhance attraction. Fisheries Management and Ecology, 8: 95-105. Chunnett, Fourie and Partners. (1990). Water resources: Planning of the Sabie River Catchment. Unpublished Report to the South African Department of Water Affairs, Pretoria, South Africa. DWAF (Department of Water Affairs and Forestry). (2005). Flow Records of Incomati River System monitoring stations. Department of Water Affairs, Pretoria, South Africa. Accessed September 2012 at URL: http//www.dwaf.gov.za. DWAF (2009). Integrated water quality management plan for the Vaal River system: Task 2: Water quality assessment of the Vaal River system. Report No. P RSA C000/00/2305/1. Directorate National Water Resource Planning, Department of Water Affairs and Forestry, Pretoria, South Africa. p. 252. Fouché, P.S.O. and Heath, R.G. (2013). Functionality evaluation of the Xikundu fishway, Luvuvhu River, South Africa. African Journal of Aquatic Science, 38(Suppl.): 69–84.

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Gagiano, C.L., (1997). An ecological study on the tigerfish Hydrocynus vittatus in the Olifants and Letaba Rivers with special reference to artificial reproduction. Unpublished M.Sc. Thesis, Rand Afrikaans University, Johannesburg, South Africa. Gallagher, A.S. (1999). Barriers. In: Bain, M.B. and Stevenson, N.J. (eds.). Aquatic habitat assessment: common methods. American Fisheries Society, Bethesda, Maryland. pp. 135-147. Katopodis, C. (1989). A Guide to Fishway Design: Working Document. Freshwater Institute, Central and arctic Region, Department of fisheries and Oceans. Canada. Katopodis, C. (1992). Introduction to fishway design. Unpublished working document. Winnipeg, Freshwater Institute. p. 62. Kleynhans, C.J., Louw, M.D. and Moolman, J. (2007). Reference frequency of occurrence of fish species in South Africa. WRC Report No. TT331/08. Department of Water Affairs and Forestry (Resource Quality Services) and the Water Research Commission, Pretoria, South Africa. Larinier, M. (2000). Dams and fish migration. Prepared for Thematic Review II.1: Dams, ecosystem functions and environmental restoration. World Commission on Dams: environmental Issues, Dams and Fish Migration, Final Draft, June 30 (2000). Larinier, M., Travade, F. and Porcher, J.P. (2002). Fishways: biological basis, design criteria and monitoring. Bulletin Franҫais de la Pêche et de la Pisciculture, 364 (Suppl.): 208. Lucas, M.C and Baras, E. (2001). Migration of Freshwater Fishes. Oxford, Blackwell Science. p. 420. Marmulla, G. (2001). Dams, fish and fisheries: opportunities, challenges and conflict resolution. FAO Fisheries Technical Paper. No. 419. Fisheries Resources Division, FAO Fisheries Department, Rome, Italy. p. 166. Peake, S. (2004). An evaluation of the use of critical swimming speed for determination of culvert water velocity criteria for smallmouth bass. Transactions of the American Fisheries Society, 133: 1472–1479. Pon, L.B. 2008. The role of fish physiology, behaviour, and water discharge on the attraction and passage of adult sockeye salmon (Onchorhynchus nerka) at the Seton River Dam Fishway, British Columbia. Unpublished M.Sc. Thesis, University of British Columbia, Canada. Roscoe, D.W. and Hinch, S.G. (2010). Effectiveness monitoring of fish passage facilities: historical trends, geographic patterns and future directions. Fish and Fisheries, 11: 12-33.

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Rossouw, J., Rooseboom, A. and Wessels, P. (1995). Laboratory calibration of compound sharp-crest and crump weirs. WRC Report No 442/1/95. Water Research Commission, Pretoria, South Africa. Scott, L.E.P., Skelton, P.H., Booth, A. J., Verheust, L., Harris, R. and Dooley, J. (2006). Atlas of southern African freshwater fishes. Smithiana Monograph 2, The South African institute for Aquatic Biodiversity, Grahamstown, South Africa. Skelton, P. (2001). A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa. Weeks, D.C., O’ Keeffe, J.H., Fourie, A. and Davies, B.R. (1996). A pre-impound study of the Sabie-Sand River system, Mpumalanga with special reference to the predicted impacts on the Kruger National Park. Volume One: The ecological status of the Sabie-Sand River system. WRC Report No 294/1/96. Water Research Commission, Pretoria, South Africa.

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DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT

MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH

AFRICA

CHAPTER 4: Case Study & Lessons Learnt

Evaluation of the fishway at the DWS Blouputs/Sendelingsdrift Gauging Weir (D8H017), Orange River, Northern Cape Province

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4.1. INTRODUCTION

This thesis forms part of an overall project that culminated in the design and implementation of fishways throughout South Africa. The project sought to better cater for the biological requirements of the fish expected to utilise a fishway, rather than being an engineering structure with purely engineering dimensions, with the foremost important criterion being that of ensuring hydraulic functionality and structural integrity, with the biological requirements being regarded as secondary. The overall project developed over a relatively long time, as did the refinement of the fishway designs that culminated from it. Therefore, much time elapsed that allowed for the critical evaluation of existing structures as well as those structures that were still in their development stages.

Improved cooperation between fish biologists and engineers was heralded as a major step forward that emanated from this research project. What did remain, however, is that the biologists aspired to develop a design with optimal functionality under all flow conditions, whereas the engineers remained more practical in their approach and often questioned the viability of constructing what were sometimes criticised as being overly complicated designs. An example of this was where Department of Water and Sanitation (DWS) committed to constructing a fishway that was replicate of the vertical slot fishway design utilised for the laboratory experimentation of the project at Balule Weir in the Kruger National Park. Upon completion, feedback from the design and construction teams (pers. comm. 6Wessels, 2013) indicated that the construction and implementation of the design was cumbersome to the point of being inhibitory, relatively expensive and the construction process was slow to complete. This factor therefore clearly requires focused attention.

Through their professional qualification, the engineers often had a better understanding of river hydraulic functioning and flow dynamics than that of the biologists. Engineers also tended to understand the restraints of design and construction given that the

6Dr Pieter Wessels, Personal Communications, Civil Engineer. Department of Water Affairs, Pretoria, March 2013.

176 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT construction of a fishway required flashing (moulds) and cast concrete with the use of heavy machinery. They also understood the limitations of site access for the heavy machinery as well as budgetary constraints. All of these factors put limitations on the degree of design complications that the biologists were aiming to implement, which ultimately meant that, going forwards, a compromise had to be reached. The mutually beneficial relationship between the engineers and biologists became increasingly apparent as the project progressed and the gaps in professional knowledge were explored.

The vast majority of instream barriers (weirs, dam walls and causeways) are located where suitable foundation material is found, which often coincides with bedrock and other suitable topographical features. The site features that make for a suitable locality for instream barrier construction very often eliminate the potential for establishing a bypass channel for fish to circumnavigate the barrier. This very often means that the vast majority of fishways are then also established as formal instream infrastructure. Negative impacts to sensitive aquatic habitat units emanate from the development of the barrier infrastructure and the fishway itself, especially during the construction procedures, and these impacts perpetuate together with the length of the construction phase. It would therefore be beneficial to the ecological integrity of a river system to construct a relatively simple, streamlined design of a fishway that would enable the reduction of the overall impacts pertaining to the actual construction of that fishway. It is also generally preferable to construct instream infrastructure during low-flow seasons for practical and safety reasons, which further limits the timeframes available for the construction phase. Focal points of the design criteria of a fishway require that the fishway be functional during the main migratory periods for the majority of the fish communities within the reach and that falls within the hydraulic limits applicable to the migratory biota within the river reach. The implementation of a more economical fishway at a particular site within a shorter period of time (construction period), that remained ecologically functional is therefore considered a successful mitigation measure to overcome the impacts of the development of an instream migratory barrier.

The DWS identified the need for a flow-gauging weir downstream of Augrabies Falls along the Orange River (Northern Cape Province, South Africa) (Figure 4-1), which presented itself as an opportunity to put into practice the lessons learnt from this research project. In consultation with design engineers at DWS, a simplified fishway,

177 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT based on the vertical slot design, was constructed. This chapter aims to present an actual case study that culminated from the outcomes of the research from this.

The aim of this chapter was to determine the functionality of the fishway at Blouputs by (1) determining which species and in what abundance were using the fishway; (2) the hydraulic conditions of the fishway associated with fish movement; and (3) to assess the effectiveness of this fishway for passage of a community of South African species of fish.

Figure 4-1: Relative localities of the various artificial and natural migratory barriers located between the Orange River mouth and Blouputs Weir (western region).

4.2. LOCALITY & HYDROLOGICAL CHARACTERISTICS OF THE RIVER REACH

The Orange River is the largest perennial river in South Africa, with a catchment area of approximately 973,000 km2 (Ramollo, 2011; DWA, 2013) that is shared by South Africa, Lesotho and Namibia and yields over 20% of South Africa’s freshwater (Figure 4-1 and Figure 4-2). It rises in the Maloti Mountains in Lesotho and flows westwards through the semi-arid and arid Southern Free State and the Northern Cape Province 178 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT and flows into the Atlantic ocean at Alexander Bay/Oranjemund. There is a strong rainfall gradient from east to west (Mucina & Rutherford, 2006), and rainfall varies from over 1000 mm per annum in the eastern highlands in Lesotho to less than 50 to 100 mm per annum along the Atlantic seaboard. As a result, over 90% of the mean annual runoff of the catchment is derived from the upper areas of the catchment, including the Vaal River, which is a major tributary of the Orange River (Benade, 1993). It is highly regulated through several weirs and major dams such as the Gariep and Vanderkloof dams (Figure 4-2). These dams were constructed to satisfy the demands for human consumption, mining and agriculture, which supports the economy of South Africa (Benade, 1993; Tooth & McCarthy, 2004).

Figure 4-2: Relative localities of the various artificial and natural migratory barriers located between the Blouputs Weir and the source (eastern region).

Accoring to Benade (1993), anthropogenic changes in the Orange River system have already resulted in a threat to the survival of certain fish species, like A. sclateri, L. kimberleyensis and L. umbratus. Despite the large size of the river, it supports a relatively low diversity of fish. The fish species community is dominated by cyprinids (minnows, mudfishes and yellowfishes).

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The Orange River System appears to display a one in 10 to 15 year episodic flood cycle (Benade, 1988), but floods can also occur every five to 10 years (Department of Information, 1971). Annual flow as well as floods and flow cessations are unpredictable due to the fact that rainfall in the catchment is extremely erratic and can at times be restricted to only certain sections of the catchment (Benade, 1988). Flow records, dating back to November 1913, indicate the maximum run-off for any particular hydrographic year to be 19, 431 X 106 m3 (163% of the mean) (October 1924 to September 1925), with a minimum of 1, 275 X 106 m3 (11% of the mean) (October 1948 to September 1949) (Kriel, 1972). Despite such extremes, the Orange River System displays a natural flow pattern and resilience, which provided the framework within which its ecosystem evolved a seasonal status regarding its most important abiotic factors, i.e. flow, temperature, oxygen, turbidity (including suspended solid transport), mineral content and most likely also pH (Benade, 1993). Episodic flood events serve as driving forces behind the ecological functioning of the system (Benade, 1988), as do minor to medium maintenance floods (Benade, 1993).

The construction of the Vanderkloof Dam (operational since 1977) has seen a regulation of the natural flow regime of the middle reaches of the Orange River, with the outflows managed to maintain hydropower generation and supply of irrigation water to downstream users (Earle et al., 2005). Seasonal flow volumes have since changed to a 59% and 41% summer and winter flow distribution, respectively (Benade, 1993). Together with the Gariep Dam, the Vanderkloof Dam (two of the largest dams in South Africa [Earle et al., 2005]) also has a dampening effect on floods in the lower Orange River as these two impoundments are capable of totally or partially absorbing the minor to medium floods required for ecological and environmental maintenance (Benade, 1993).

The Blouputs fishway is located along the Orange River approximately 18 km downstream of Augrabies Falls, within the Lower Orange River Water Management Area (DWAF, 2002). Benade (1993), using flow data from Boegoeberg Dam (located approximately 303 km upstream of the site) as a point of reference for the period 1914- 01-01 to 1989-04-30, showed that this river reach displays natural seasonal flow regimes. Analysis of the natural flow patterns showed that 82% of natural flow occurred during the summer (October to May) and 18% during the winter (May to October) cycles, with minimum and maximum flows recorded during August and February, respectively. The system was also shown to display erratic peak flows coupled 180 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT with high silt loads (Wellington, 1933; 1958; Chutter, 1973; Tomasson, 1983; Tomasson & Allanson, 1983; Benade, 1993), which is largely due to the erratic rainfall patterns within the region and can be restricted to only certain sections of the catchment (Benade, 1988).

The DWS identified the need for a flow-gauging weir on the Orange River at Blouputs in the Northern Cape Province, located approximately 18 km downstream of Augrabies Falls (coordinates: -29°49’60” S, 21°22’60” E). As part of the Environmental Impact Assessment (EIA) process, a fishway was to be constructed in conjunction with the weir as a means to mitigate the impact of constructing an instream barrier that would effectively inhibit migratory freedom of aquatic biota within the river reach (Golder Associates Africa, 2008). A design based on the vertical slot fishway concept was chosen due to it being able to accommodate high flow variances whilst retaining functionality (pers. comm. 7Wessels, 2014). This was supported by the successful implementation of vertical slot fishways under similar conditions (Neusberg Weir vertical slot fishway) (Benade et al., 1995). This was important as the Orange River, even though highly regulated due to upstream impoundments, remains strongly influenced by seasonality due to its large catchment size. The upstream-located Van Der Kloof Dam incorporates hydroelectric power infrastructure and water is released from the dam to satisfy power generation demands, which is within a magnitude of approximately 300 m3/s. Releases of variable volumes to satisfy irrigation volume demand for downstream users are also routinely performed. These flow volume releases lead to unseasonal freshet flows throughout the river reach, which further increases the flow volume variances experienced within the system. An indication of the variance in hydrology of the Orange River at the Blouputs site is presented in Figure 4-3, which shows that average high flow and low flow volumes range between 1093.33 m3/s (February average) and 38.03 m3/s (November average). These values were taken from the D7H014 DWS abstraction weir at Neusberg, located approximately 75 km upstream. These figures are representative of the average variance in flow volume rather than absolute discharge values. The utilisation of the Neusberg Weir as a reference is due to the unavailability of data for the newly constructed Blouputs Weir.

7Dr Pieter Wessels, Civil Engineer. Department of Water Affairs, Pretoria, February 2014.

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4000

3500

3000

2500

2000

1500

1000

500

0 2009-08-01 2010-02-01 2010-08-01 2011-02-01 2011-08-01 2012-02-01 2012-08-01 2013-02-01 2013-08-01 2014-02-01

Figure 4-3: Average monthly flow discharges for the Orange River at the DWS Neusberg Weir for the period August 2009 to April 2014.

An analysis of the flow-rated total surface water discharge taken for the DWS Neusberg Weir for the period 13/07/1993 to 24/07/2012 was sourced from the DWS online hydrology database (DWA, 2012). This presents a flow-weighted yield analysis, which is an indication of the percentage of time that a certain discharge rate can be expected within the system over that period. The design parameters of the gauging weir at Blouputs make provision for it to tend toward drowned-out hydraulic conditions8. The weir tends to drown out and does not pose as a migratory barrier to fish when the change in upstream and downstream water levels approach 200 mm (the same change in water levels as what are experienced within the fishway). This occurs when the river discharge rate exceeds approximately 320 m3/s and therefore the fishway would not be required to function at flow rates exceeding this volume. From the flow data for the river this would occur (on an annual basis) approximately 68% of the time, and it is possible to occur within all the months of the year (Figure 4-4).

8 Drowned-out conditions occur due to the increase in water turbulence levels downstream of the weir that creates greater resistance to flow. The flow upstream of the weir is not subject to the same turbulence and resistance and therefore the velocity is greater. Due to this, the water levels rise up downstream of the weir as flow rate increases.

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Figure 4-4: Proportion of time that the river flow rate is expected to exceed 320 m3/s as a proportion of when it is expected to be less than 320 m3/s (based on data for the Orange River at the DWS Neusberg Weir [DWA, 2012]). This is an indication of the time proportions when the gauging weir tends toward drowned-out hydraulic conditions and will no longer present as a migratory barrier to fish.

4.3. FACTORS AFFECTING FISH MIGRATIONS WITHIN THE RIVER REACH

The integrity of the fish species community structure within the Orange River is impacted by fragmentation due to the high number of impoundments (29 instream barriers e.g. dams and weirs) that occur along its major watercourse (Earle et al., 2005). Of greater relevance to this case study that influences the fragmentation of fish community structures at a more local scale is the occurrence of natural migratory barriers (Ramollo, 2010; 2011) as the largest waterfall (Augrabies Falls) that occurs along the watercourse is located within the survey area.

The Orange River enters the Atlantic Ocean at Oranjemund approximately 560 km downstream of the site. A noteworthy natural migratory barrier that occurs within the river reach is at Orange Falls (also known as Ritchie Falls), which is a natural series of cascade waterfalls located approximately 120 km downstream of the Blouputs site.

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The watercourse at this site is characterised by a series of interconnected channels. An eastern channel plunges through a narrow gorge that presents difficult hydraulic conditions for fish passage, with high velocity and high volumes of water that flows through a constricted narrow channel over a steep gradient. The narrow constriction means that this barrier would drown out at moderately high flows, but also means that it would result in high water velocities. Channel characteristics during flood conditions usually allow for peripheral zones of slow-flowing water. The eastern channel at Orange Falls is characterised by steep, bedrock-dominated banks that does not allow for slow-flowing water. These characteristics induce hydraulic conditions that are difficult for fish to negotiate. The western channel flows along an elevated plateau through a series of interconnected channels before plunging through a boulder-strewn steep area. This section would only allow fish passage during extreme flood flow conditions. Therefore, as a whole, Orange Falls represents a migratory barrier only during low flow periods, and would be passable under moderate flood conditions, where higher flows would make it accessible to fish movement (unpublished monitoring data, 2014). Approximately 18 km upstream of the site is Augrabies Falls, which presents an absolute natural barrier to upstream passage for fish and any passage upstream across this barrier is considered highly unlikely (excepting for the eel species, A. mossambica that has been recorded from the river reach (Benade, 2003). Verified scientific accounts of this species within the river reach are lacking (Scott et al., 2006; Kleynhans et al., 2007). This barrier also forms the geographical distributional barrier to Barbus hospes (Namaqua barb). The Augrabies Falls also poses as the upper geographical distribution barrier to B. hospes making this species endemic to this river reach. The Augrabies Falls also poses as a barrier to the isolated population of Mesobola brevianalis (River sardine) that occurs within the Lower Orange River (Skelton, 2001; Scott et al., 2006). Another naturally occurring feature within the river reach is the Orange River Gorge. This is an approximately 18 km section of the river located downstream of the Augrabies Falls characterised by fast-flowing deep water that offers little hydraulic refuse to fish and invertebrates. Aquatic macro-invertebrate diversity is naturally low within this stretch (Dallas, 2007) and is generally inhabited by only larger-bodied and stronger-swimming fish species due to substrates and hydraulic conditions that are not amicable to supporting high fish densities and species diversity.

The weir at Blouputs is neither the first nor the only artificial migratory barrier located on the Orange River between the river mouth and Neusberg Weir, which is a stretch of approximately 600 km. Various other impounding structures (abstraction weirs, diversion weirs, gauging weirs) also occur. The localities of these structures are 184 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT

presented in Table 4-1, with their relative localities being presented graphically in Figure 4-1 and Figure 4-2.

Table 4-1: Details of the various artificial migratory barriers located between the Orange River mouth and Blouputs Weir.

Locality Name Type Notes Latitude (S) Longitude (E) Fitted with a pre barrage-type Sendelingsdrift DWS gauging weir S28° 04’ 33.0” E16° 53’ 54.2” fishway No fishway and fish could only Abstraction/diversion Vioolsdrift S28° 45’ 45.0” E17° 43’ 43.2” migrate across the weir under weir flood conditions Partial weir of a single channel in Abstraction/diversion a multi-channel system. Has a Onseepkans S28° 44’ 29.1” E19° 23’ 09.2” weir marginal impact on migratory freedom of fish within the reach Abstraction/diversion 3 to 4 m high, constructed circ. Farmer’s weir S28° 31’ 57.6” E19° 39’ 56.3” weir 1930

Difficult hydraulic conditions are also encountered throughout many sections of the watercourse, where smooth bedrock dominates narrow, deep channels. High water velocities and uniform flow create difficult hydraulic conditions for fish to negotiate within the sections of river. The flow-gauging weir at Blouputs occurs within an area that offers suitable aquatic habitat that would support a wide diversity of fish and aquatic macro-invertebrate species. Further fragmentation of the fish populations through the establishment of the weir at Blouputs would exacerbate the impacts to the fish population fragmentation within the river reach that have to contend with a series of natural and artificial hydraulic barriers. Measures to ensure longitudinal connectivity of this section of river were therefore necessary to aid in maintaining accessibility to areas that offer habitat diversity within the system.

4.4. FISH COMMUNITY STRUCTURES WITHIN THE RIVER REACH

The river reach below Augrabies Falls is regarded as a hotspot for both species diversity and endemic freshwater species richness supporting populations of Namaqua barb (B. hospes) and River sardine (M. brevianalis) (Jubb & Farquharson, 1965; Jubb, 1967; Skelton & Cambray, 1981; Benade, 1993). The fish species recorded from the Lower Orange River are presented in Table 4-2, together with their known migratory requirements (from Bok et al., 2007).

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The fish species community of the Lower Orange River is made up of predominantly potadromous species (migrating only within freshwater environments) and one amphidromous species, namely the catadromous A. mossambica, which enters the Orange River from the Atlantic Ocean to reach sexual maturity after breeding within the marine environment (Skelton, 2001).

Table 4-2: All fish species recorded from the Lower Orange River that would be impacted by the establishment of a migratory barrier (from Benade, 2003), together with their recommended hydraulic limits (from Bok et al., 2007).

Migratory requirements* Common Biological factors Hydraulic limits Species Body form name Spatial Importance V ∆H Pv range Anguilla Longfin eel Anguilliform 5 5 1.4 100 150 mossambica Austroglanis Rock catfish Siluriform 3 1 1.5 120 180 sclateri Mesobola River Fusiform 4 3 1.7 150 180 brevianalis sardine Barbus Threespot Fusiform 4 3 1.7 150 200 trimaculatus barb Barbus Namaqua Fusiform 4 3 1.7 150 200 hospes ** barb Barbus Straightfin Fusiform 4 3 1.5 120 200 paludinosus barb Vaal-Orange Labeobarbus largemouth Fusiform 5 3 2.0 200 220 kimberleyensis yellowfish Vaal-Orange Labeobarbus smallmouth Fusiform 4 3 2.0 200 220 aeneus yellowfish Orange Labeo River Fusiform 5 3 1.7 150 180 capensis mudfish Cyprinus Carp ALIEN SPECIES carpio Labeo 1.7- 150- Moggel Fusiform 4 3 300 umbratus 2.0 200 Clarias Sharptooth Siluriform 2 3 1.7 150 180 gariepinus catfish Pseudocrenila Southern Compressiform 1 1 1.7 150 180 brus philander mouthbrooder Tilapia Banded tilapia Compressiform 2 3 1.7 150 180 sparrmanii Oreochromis Mozambique Compressiform 2 3 1.7 150 180 mossambicus tilapia * Migratory requirements: Importance: 1=low (not vital for survival); 3=med; 5=high (vital to complete life cycle). Distance: The distance that each species is known to migrate: 1 within river reaches; 3 between river reaches; 5 catchment scale; V - Velocity (m/s): The maximum known water velocity that a species can swim against; ∆H - Height (mm): Recommended maximum height between successive pools; Pv - Turbulence (Watts/m3): The recommended maximum levels of turbulence that a species can endure within each pool. ** Barbus hospes: This species does not appear in the migratory database of Bok et al., 2007. Figures provided here are extrapolated from similar species with similar morphometrics. The habitat types where this species are found are also taken into consideration when setting comparable limits.

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From Table 4-2 species that occur within the river reach regarded as obligatory migratory species are A. mossambica, L. kimberleyensis, L. aeneus and L. capensis. These species move long distances within the river system cyclically throughout their lives either to complete a stage of their life cycle or to breed, and therefore require migratory freedom for long-term survival of the species or vigour of the population. There are also species regarded as local migratory species, that move seasonally largely within the river reach in order to exploit habitat that becomes available through the natural cyclic variations of the river system (e.g. floodplains that only develop during the rainy season, or riverine habitat types (biotopes) that develop through seasonal hydraulic changes of the river). This type of habitat exploitation is very often utilised for breeding purposes and is particular to the smaller species within the river reach such as the barbines (B. trimaculatus, B. paludinosus, B. hospes and M. brevianalis). Another species largely confined to locally suitable habitat and is not known to undertake migrations over any significant distances is A. sclateri. The migrations undertaken by species representative of the Cichlidae family (Oreochromis mossambicus [Mozambique tilapia], P. philander and T. sparrmanii) are generally thought to be limited to habitat exploitation to locate suitable breeding habitat at the local scale, for foraging purposes, temporary predator evasion or to avoid unfavourable habitat conditions). What does require migratory freedom, and is particular to all of the abovementioned species, is the ability to exploit further reaches of a river system for the purpose of genetic dispersal. A fishway that is deemed ecologically functional for the river reach would therefore be required to cater for the migratory needs for all of these species. This fishway should cater for the weakest-swimming species recorded within the system, which is shown to be A. mossambica. A fishway that can cater for eels such as this species requires specific modifications to the design and features to cater for the requirements of this species (Bok et al., 2007). This species has a low rate of occurrence within the river reach (Benade, 2003) and so it was deemed uneconomical and unfeasible to focus the design of the fishway to cater specifically for this species. This species was therefore not considered when establishing the design criteria for the fishway.

According to Kleynhans et al. (2007) the reference fish species data that are perhaps more relevant to the river reach are those presented by the DWS FROC (Frequency of Occurrence) data specific for the Blouputs Weir site. These species, their FROC for Blouputs as well as for a reference site located at Onseepkans (located approximately 115 km downstream) are presented in Table 4-3.

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According to the biological data gathered from the fish community structures within the river reach and their respective known swimming abilities and limitations (from Bok et al., 2007), the fishway should not exceed water velocities between successive pools of 1.5 m/s. It should also not have a drop between pools of greater than 150 mm and a turbulence level within each pool should not exceed 180 watts/m3.

Table 4-3: Reference species Frequency of Occurrence (FROC) (Kleynhans et al., 2007) relevant to the river reach including Blouputs Weir and downstream.

Species FROC Scientific Name Common name abbreviation Blouputs Onseepkans Mesobola brevianalis MBRE River sardine 1 3 Barbus trimaculatus BTRI Threespot barb 1 1 Barbus hospes BHOS Namaqua barb 1 1 Barbus paludinosus BPAU Straightfin barb 1 3 Labeobarbus Vaal-Orange BKIM 3 1 kimberleyensis largemouth yellowfish Vaal-Orange Labeobarbus aeneus BAEN 3 1 smallmouth yellowfish Labeo capensis LCAP Orange River mudfish 1 1 Austroglanis sclateri ASCL Rock catfish 3 1 Labeo umbratus LUMB Moggel 3 1 Clarias gariepinus CGAR Sharptooth catfish 3 3 Pseudocrenilabrus PPHI Southern mouthbrooder 1 1 philander Tilapia sparrmanii TSPA Banded tilapia 1 3

4.5. DESIGN RATIONALE & SPECIFICATIONS OF THE FISHWAY

4.5.1. General description of gauging weir and fishway orientation

The orientation of the Blouputs fishway in relation to the riverbanks and gauging weir is shown in Figure 4-5 as an aerial image. Figure 4-6 presents a general ground-level image of the weir and fishway orientation. The DWS (Hydrological Services) provided detailed design specifications for the Blouputs fishway and gauging weir, which are presented in Figure 4-7 and Figure 4-8. A three dimensional model of the fishway is presented in Figure 4-9. The gauging weir is made up of two crest heights. The low crest weir is located at the northern bank side of the watercourse and is at a level of 438.30 m amsl (above mean sea level). The high crest weir is located at the southern bank side and is at a level of 0.30 m higher (438.60 m).

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The fishway is constructed on the southern bank in association with the high crest weir. Flow is therefore prioritised over the low crest weir (toward the northern bank of the watercourse) and the high crest weir will only overtop at river flow rates of above 19.54 m3/s. The exit of the fishway (water inflow) is at 438.00 m (0.60 m lower than the level of the high crest weir and 0.30 m lower than the level of the low crest weir, so the first chamber is always inundated with water.

Figure 4-5: Aerial view of the fishway at Blouputs Weir to show orientation (Google Earth®, 2014). This aerial photograph was taken during the construction phase of the weir and therefore only the high crest of the weir and the fishway were functional at the time. Only the fishway (arrow) and the high crest weir are visible.

There is a sill placed between the fishway exit chamber (pool 1) and pool 2 that will only overtop when the water level reaches 438.45 m, which equates to a river flow rate of 6.91 m3/s. The fishway would, however, not be considered operational under these relatively low flow rates.

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Figure 4-6: View of the Blouputs fishway in the foreground and the Blouputs Weir from the southern bank.

The watercourse is naturally deeper toward the northern bank and therefore debris carried down by the current would be drawn away from the fishway. The southern bank of the river within this area is private property whereas the northern bank is open to the public. The decision to site the fishway along the southern banks was also to inhibit freedom of access to the public to avoid harvesting of fish within the fishway during peak migration times. This has also been cited as a problem that has an impact on fishways within South Africa (Fouché, 2009; Fouché & Heath, 2013). The decision behind running the fishway channel parallel to the weir rather than the more traditional orientation of being perpendicular to the weir was mainly due to accommodating local topographical features. The fishway channel running parallel to the weir also meant that, if the weir overtops during flood events, it would overflow into the top few buckets first. This would mean that a degree of functionality of the fishway would still be retained. Orientating the fishway channel perpendicular to the weir would mean that flood events that overtop the fishway infrastructure would render the fishway completely ineffective.

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Figure 4-7: A top view of the design specification of the fishway implemented at Blouputs (provided by DWS, Hydrological Services, Pretoria).

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Figure 4-8: A side view of the design specification of the fishway implemented at Blouputs (provided by DWS, Hydrological Services, Pretoria).

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Figure 4-9: Three-dimensional figure of the fishway at Blouputs (not to scale) (three-dimensional modelling developed by Ansara Architects).

4.5.2. Fishway specifications

The fishway at Blouputs was based on a simplified version of the vertical slot type, and can be considered a hybrid design between a vertical slot and pool and weir fishway. Favourable characteristics of the vertical slot design include that it remains functional over a wide range of flow rates, particularly as flow volumes increase. A disadvantage of the standard vertical slot design is that it requires a critical minimum flow volume in order to function, reaching optimal functionality only when submerged conditions are reached (submerged flow conditions are reached when the water level in the lower pool equals 0.667% of the upper pool level). Laboratory experimentation where design variances were tested showed that the placement of a sill fitted at the base of each slot opening enhanced the functionality of the vertical slot design at relatively lower flows (flow volumes considered to only allow sub critical hydraulic conditions within the

193 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT channel) (see Chapter 2). The design incorporated this concept by placing a sill measuring 600 mm into the bottom of each slot opening, which maintained a minimum water depth throughout the fishway channel of 600 mm. It was also postulated that this would allow for persistence of pool volume so fish could remain within the channel under very low flow conditions.

The great variability in flow of the river meant that, for the fishway to be considered feasible, the fishway needed to be designed to operate at full functionality only over a certain period of time, which coincides with peak migratory times of the fish species community identified from the river reach. This period also, however, coincides with flood seasons, where the interaction with floating debris around and within the fishway infrastructure would be inevitable. This could be in the form of tree trunks and branches that would hit the fishway with considerable force when carried by the currents generated under flood conditions. Structural integrity was one of the primary concerns, and a reason for the decision to make all of the fishway walls and internal structures 500 mm wide. Debris that blocks the intake of the fishway, even for a short period over the peak migratory times, could have profound impacts to the ecological functionality of the fishway. Indeed, the soiling of a fishway with debris has been identified as a maintenance concern with most fishways (Coax & Welcomme, 1998; Bok et al., 2007) and therefore the fishway exit was designed to reduce the debris intake by reducing the flow velocity of the water into the fishway at the exit point. The intake of the fishway is positioned perpendicular to the water flow and therefore most of the floating debris will merely be deflected away from the inflow.

The fishway exit (inflow) is 900 mm wide, whereas all the proceeding slots measure 300 mm wide, which reduces the flow velocity of the water at a given discharge rate. The level of the exit is higher than that of the low crest weir by 150 mm, but lower than the high crest weir by 150 mm, meaning that there is a minimum flow depth required over the weir before water flows through the fishway. This goes against present conventional thinking, which dictates that the flow through the fishway should be prioritised before the weir overtops so that the fishway can function over a longer period of time. Floating debris and the consequential clogging of the fishway with debris, as mentioned above, is a major maintenance issue that effects the functionality of a fishway. By not prioritising the flow through the fishway means that debris will merely flow over the weir and the potential for this debris entering into the fishway will be reduced. The intake to the first chamber is also designed to be lower than the 194 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT second chamber by 450 mm, which further reduces the water velocity into the fishway, which decreases the chances of debris being actively drawn into the fishway. The reduced chances of debris entering into the fishway would allow for greater hydraulic functionality and overall lower maintenance requirements. The fishway therefore only begins to operate once the water level over the low crest weir exceeds 150 mm. The fishway is made up of 17 consecutive pools, with three bend points. The first four of the fishway pools at the exit (top) run parallel within the watercourse after which there is a 90° bend away from the watercourse (parallel to the weir). This bend point (Pool 5) incorporates a larger pool than the previous ones. After a further five pools the fishway turns back on itself, and the fishway is directed back toward the watercourse, with the bend point including a pool that incorporates a double-volume resting pool (Pool 11). The incorporation of a double-volume pool serves various functions. Firstly, it creates a practical means to direct the fishway channel back on itself, which is necessary to bring the channel back toward the watercourse. Secondly, the larger pool acts as a turbulence dissipater. Turbulence levels build up within a fishway channel from pool to pool, with a consequential decrease in submergence ratios occurring as the water flows through the channel. By providing a double-volume pool, the turbulence levels have a chance to dissipate and the submergence ratios are effectively reset. This is the reason why it is not recommended that a vertical slot fishway incorporate more than nine consecutive pools without the provision of a larger volume settling pool. This settling pool then has the further function of providing fish a quiet resting pool where they can recover from swimming efforts. The entrance (bottom) of the fishway (pool 17) is also a larger volume pool and is located at the base of the weir where a water deflection wall directs water from further along the weir base toward the fishway entrance to increase the attraction flows to the fish (Figure 4-10).

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Fishway entrance Deflection wall to increase the attraction flows at the fishway entrance

Figure 4-10: The entrance of the fishway showing the deflection wall that directs overflow water toward the entrance to increase attraction flows toward the entrance to help fish to locate it.

The internal dimensions of each pool are 1800 mm (length) x 1500 mm (width), with a dividing wall thickness of 500 mm between pools, giving each pool and effective length of 2300 mm. The slope of the fishway is 1:11, with a 200 mm drop between pools. Experimentation of a scale model vertical slot fishway indicated that performance of the fishway could be improved by placing a sill at the bottom of each slot opening (from Chapter 2), and therefore the most noteworthy deviation from the traditional and standard vertical slot design is the placement of the sill in each slot opening. The sill is measures 600 mm high and functions to create a pooling effect of the water within each pool that maintains a minimum pool depth of 600 mm. This modification allowed for greater functionality at low flow rates, as indicated by experimental hydraulic and biological testing. Because of this, the fishway would remain functional over a greater period as optimal submerged flow conditions would not necessarily be required for proper functionality of the fishway. This means that the fishway would operate under relatively lower discharge rates. The upper surface of the sill is sloped at 45º toward the downstream side (Figure 4-11). Sloping the upper surface of the sill was done in order to reduce the chances of breakaway between the flowing water and the baffle surface, which would otherwise create an air cavity and increase the degree of difficulty for the fish to get through the slot openings.

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Figure 4-11: The vertical slot between two successive pools showing the sloped upper surface of the sill.

The fishway was designed to allow for a compromise between ease of design, practical construction, and ecological functionality. No baffles (current deflectors) were placed within the pools either (shown in Figure 4-12), which further deviates from the traditional vertical slot design (as shown in Figure 4-13). Baffles within the pools act as current deflectors to dissipate the velocity of the water as it flows from the slot opening into a pool. The more that the water velocity entering into the pool is dispersed within the pool, the more the turbulence levels can be dissipated. It has been found, however, that these internal baffles created lateral currents that enhanced breakaway of the flowing water from the vertical walls as the water flows through the slots. This breakaway of the water meant a constriction of the actual width (narrower than the actual slow opening), which effectively increased the water velocity as it flowed through the slots.

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Figure 4-12: View of the Blouputs fishway showing the upper and lower levels of pools.

Figure 4-13: View of the larger resting pool that incorporates the second turning point of the fishway.

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4.5.3. Fishway hydraulics

The height of the water level over the low crest weir was measured during the time of each survey. The level of the water flowing into the fishway (H1) could be extrapolated from this because all of the relative heights of the infrastructure were known. From H1, the discharge, differences in water levels between the pools, water velocities through the slots and the resulting turbulence levels in each pool of the fishway were calculated. The equations used to calculate these variables are given in Chapter 2.

River flow volumes at the time of sampling were requested directly from DWS Hydrological Services for the Blouputs Weir as the routine flow measurements were not yet operational. Flows for survey 1 (February 2014), survey 2 (April 2014) and survey 3 (September 2014) were 35.89 m3/s, 101.79 m3/s and 20.674 m3/s, respectively. The data are provided as the height of the water level as it flows over the low crest weir. By utilising hydraulic calculations (see Chapter 2), and by knowing the levels of the fishway in relation to the low crest and high crest weirs, the discharge rates through the fishway can be calculated, and in turn, the exact water velocities through the slots and the respective turbulence levels within each pool as well. The hydraulic conditions within the fishway during at the time of the surveys are presented in Table 4-4 and Figure 4-14.

Table 4-4: Hydraulic conditions within the fishway at the sampling times.

Fishway hydraulic details Low River crest Change in Survey Date flow level height Vs Pv 3 H1 (m) H2 (m) Q (m3/s) (m) (m /s) between (m/s) (watts/m3) pools 1 26/2/14 0.406 35.89 0.256 0.056 0.0671 200mm 1.294 64.5 2 25/4/14 0.681 101.79 0.531 0.331 0.1611 (remains a 1.864 113.5 3 11/9/14 0.379 31.05 0.229 0.029 0.0582 constant) 1.224 58.0

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Submerged flow conditions 2

1 3

Figure 4-14: Hydraulic characteristics of the fishway at Blouputs, showing hydraulic conditions during survey periods and indicating the discharge volume where submerged flow conditions occur. The labels correspond to hydraulic conditions at the survey times (Table 4-4), where Qw=flow volume in m3/s (left axis), Vslot=flow velocity through the slot of each pool of the fishway in m/s (left axis); Vol=pool volume in m3 (left axis) and Pvw=turbulence levels within each pool in watts/m3 (right axis). An indication of the ecological functionality of the fishway is provided as the red/green arrow, showing that the fishway gains functionality as the discharge increases.

4.6. MONITORING OF THE FISHWAY

4.6.1. Fishway survey orientation

The fishway pools were numbered from the top (water inflow/exit) through to the bottom (water outflow/entrance) in numerical order (Figure 4-15). There are 17 pools in total, with the inflow chamber (fishway exit) labelled as Pool 1, and the last pool (fishway entrance) labelled as Pool 17. The lower level pools (Pools 12 to Pool 17) had water depths shallow enough to practically allow for comprehensive electro-fishing and therefore three pools were selected within this row, namely Pool 17 (entrance), Pool 15, Pool 13 and Pool 11 (the larger resting pool where the fishway channel turns

200 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT back on itself). The upper level (Pools 5 to 11) were surveyed using cast netting due to excessive water depth. This technique was not regarded as being comprehensive and therefore every pool was sampled in an effort to gain maximum potential results. The exit to the fishway and pools 1 to 4 were inaccessible due to secure metal grid covers.

Figure 4-15: Diagrammatic representation of the fishway at Blouputs Weir showing pool numbering (three-dimensional modelling developed by Ansara Architects).

4.6.2. Sampling methodologies

The lower pools (Pools 12 to 17) were surveyed using electro-fishing, whilst a cast net was utilised within the upper pools (Pools 5 to 11) due to the water depth within these upper pools being too deep to allow for standard electro-fishing techniques. Five minutes were spent electro-fishing within each pool using a 1000 Watt 220 Volt AC generator (Engel) and standard electro-shocker device. This duration was deemed adequate to comprehensively sample each pool due to their relative small size (1.5 m x 1.8 m). The entrances and exits of the pools that were surveyed were closed off with framed nets to prevent fish from escaping. The deeper upper pools were sampled using a cast net. This method could not be regarded as a comprehensive collection technique due to the currents within the pools that did not allow the net to settle evenly.

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It did allow for an indication, however, of what individuals and species were present. Captured fish were identified and measured (to the nearest 5 mm total length (TL)) during each sampling effort to enable generalised size-class grouping (adults, juveniles, etc.) before they were released into river upstream of the weir.

It should be noted that this survey was limited to assessing the ability of the fish to ascend the fishway and was not able to determine what proportion of the overall fish population was utilising the fishway. It was also not able to determine how successful fish were in locating the entrance of the fishway and therefore only general observations were indicated in this regard. Surveying of the fishway was also limited to three survey periods and no long term monitoring has yet been undertaken.

4.7. FISH ASSEMBLAGES IN THE RIVER REACH

The historical and expected fish diversity in the Orange River at the site was taken from the DWS FROC reference site: D8ORAN-BLOUP, located at S28° 30’ 40.1”; E20° 10’ 29.4” (Kleynhans et al., 2007) and these data were verified through sampling surveys undertaken within the river reach as part of this study. Fish surveys were also undertaken at Onseepkans and Orange Falls, both sites located downstream of Blouputs, six months prior to the fishway monitoring. The fish community structures downstream of Blouputs Weir were also surveyed at the time of the monitoring of the fishway. All surveys utilised standard and accepted sampling techniques, namely electro-fishing and cast netting. No formal analysis of the fish communities was undertaken, as the aim of the fish survey was to gain an understanding of the fish community structures occurring below the weir as well as these species that presumably would utilise the fishway for upstream passage.

The results of the survey for fish from the river directly below the Blouputs Weir are presented in Table 4-5. From these results it can be seen that there was a combination of adult and juvenile size classes for most species, with a species diversity of nine having been collected from the river. The expectation of what species should be encountered within the fishway can then be made from these results.

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Table 4-5: The fish species sampled during the time of the fishway survey, numbers of individuals, size classes and habitat type from the area immediately downstream of Blouputs Weir.

Size class Number of Habitat type Scientific Name (TL in Adults Juveniles individuals mm) SD FD SS FS Mesobola brevianalis 16 25-50 14 2 X X Barbus trimaculatus 9 45-60 9 0 X X X X Barbus hospes 6 40-55 6 0 X X X Barbus paludinosus 4 40-55 4 0 X X Labeobarbus aeneus 6 85-220 2 4 X X Labeo capensis 27 90-300 19 8 X X Clarias gariepinus 2 220-250 0 2 X X Pseudocrenilabrus philander 3 50-70 3 0 X X Tilapia sparrmanii 7 45-85 5 2 X X SD= Slow deep; FD= Fast deep; SS= Slow shallow; FS= Fast shallow (Kleynhans, 2007).

4.8. ASSESSMENT OF FISHWAY FUNCTIONALITY

For the purposes of presenting the data for the surveys, the fishway was split into two levels of pools. The division between the two levels was the larger (double size) resting pool at the turning point (pool 11), which was considered to be part of the lower level of pools. The last four pools (including the exit) (pools 1 to 4) of the fishway were inaccessible due to metal grids placed over the tops for safety and security reasons and therefore surveying within these pools was impossible, but design specifications of these last four pools indicate that they experience the same hydraulic characteristics as pools 5 to 10. For this reason, the fish that were collected within the upper level of pools (pools 5 to 10) were considered capable of successfully negotiating the full length of the fishway. This was deemed adequate as the hydraulics are repetitious from one pool to the next and having successfully already negotiated pools 17 to 11 (the fishway entrance to the larger resting pool) and then committing to further negotiating the remaining pools means that hydraulic conditions were not outside of their swimming capabilities of these species and individuals. This also meant that no bottle-necking occurred as a result of design elements that induced difficult hydraulic conditions.

Survey methods within the upper level of pools was limited to cast-netting due to the inaccessibly-deep water levels of these upper pools that made conventional electro- fishing techniques unpractical. This method was not thought to be a comprehensive sampling technique and the results are therefore considered to be an underestimate of the actual numbers of fish. The turbulence levels within the pools did not allow for symmetrical settling of the net and therefore individuals especially that were in the corners of the pool were presumably not captured. Smaller individuals of smaller

203 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT species (e.g. M. brevianalis and Barbus spp.) were also presumably able to escape through the net. This was not considered a limitation to the survey as the individuals sampled within the lower level of pools (where electro-fishing was employed) were also all shown to be within adult and sub-adult size classes, with no juveniles being noted.

4.8.1. Survey 1

Survey 1 was undertaken during February 2014 where 90 individuals representing nine species were collected within the fishway Table 4-6). Labeo capensis, B. hospes and M. brevianalis dominated the species abundance within the fishway making up 27%, 22% and 21% of the total numbers of individuals, respectively (Figure 4-16). According to Bok et al. (2007), only L. aeneus and L. kimberleyensis should be capable of negotiating drops between pools of up to 200 mm and this height difference should be a limiting factor to most other species. Noteworthy results following the first of the surveys at Blouputs fishway are that M. brevianalis, B. trimaculatus, B. hospes, B. paludinosus, L. capensis, T. sparrmanii and Clarias gariepinus (Sharptooth catfish) were all successful in negotiating the fishway. This refutes the previous notion that these species could not negotiate drops between pools larger than 150 mm (Bok et al., 2007), but successful negotiation of the fishway by these species indicate that they can overcome these drops. It was only P. philander that was relatively unsuccessful under these hydraulic conditions as it was only found within the lower level of pools (up to pool 11). Although not present within the upper level of pools and therefore excluded from the group of individuals regarded as having successfully negotiated the fishway, this species was able to negotiate similar hydraulic conditions between pools 17 and 11. Therefore, having not been sampled within the upper level pools is not regarded as being indicative of an inability to negotiate the hydraulic conditions presented by the fishway. The proportions of individuals of species sampled in the lower level of pools in relation to those sampled within the upper level of pools are presented in Figure 4-17.

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Table 4-6: Results of Survey 1 (26 February 2014) at the Blouputs fishway.

Pool 1 (Exit) (These pools were HYDRAULIC CONDITIONS: Pool 2 inaccessible due to Drop between pools: 200 mm Pool 3 secured metal grid Water velocity through slot: 1.294 m/s covers) Pool 4 Turbulence within pools: 64.5 watts/m3 Pool 5 Pool 6 Pool 7 Pool 8 Pool 9 Pool 10 Pool 11 Species (No.) Size Species Size Species Size range Species Size Species Size range Species Size range Species Size range range* (No.) range (No.) (No.) range (No.) (No.) (No.) LCAP(6) 275-305 TSPA(3) 45-55 (1xJuv) BAEN(2) 165-215 MBRE(2) 45-50 LCAP(2) 205-220 TSPA(2) 20-45 (1xJuv) MBRE(7) 60-65 0 - BHOS(5) 45-65 LCAP(3) 160-200 BHOS(5) 50-65 LCAP(1) 115 BHOS(2) 60-70 BPAU(1) 45 BTRI(3) 60-80 CGAR(1) 295 BAEN(2) 115-210 Pool 17 (Entrance) Pool 16 Pool 15 Pool 14 Pool 13 Pool 12 LCAP(9) 195-245 PPHI(4) 70-85 Species (No.) Size Species Size Species Size range Species Size Species Size range Species Size range BPAU(3) 55-75 range (No.) range (No.) (No.) range (No.) (No.) CGAR(1) 285 LCAP(1) 90 (1xJuv) TSPA(1) (1xJuv) 35 BAEN(1) 210 LCAP(2) (1xJuv) 95-160 TSPA(1) 55 Not Not sampled - - MBRE(7) 40-55 Not sampled - BAEN(1) 190 BHOS(4) 40-65 sampled BHOS(4) 40-60 MBRE(3) 40-55 CGAR(1) 175 * Size range provided as total length (TL) to the nearest 5 mm. Juv=Juvenile

Figure 4-17: The proportion of the individuals of the fish species Figure 4-16: The proportion of fish species collected within sampled during February 2014 within the fishway that were in the fishway during February 2014. the upper level of pools in relation to those surveyed within the lower level of pools.

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Although not definitive, this is a potential indication of the measure of success of the various species surveyed within the fishway. From this, B. trimaculatus showed the highest degree of success, with 100% of the individuals being located within the upper level of pool, followed by T. sparrmanii with 70% and L. capensis, with 50% of the individuals successfully reaching the upper level of pools. Tilapia sparrmanii is regarded as one of the weaker-swimming species within the system and therefore 70% of the individual reaching the upper level of pools is a promising indication that the remaining species (which are thought to have superior swimming abilities) can also successfully negotiate the fishway channel under these hydraulic conditions. This is reiterated by the surveying of juvenile T. sparrmanii in pool 7 and pool 9.

4.8.2. Survey 2

Survey 2 was undertaken during April 2014 where 97 individuals representing 10 species were collected within the fishway (Table 4-7). Labeo capensis, M. brevianalis and B. hospes again dominated the species abundance within the fishway making up 19%, 21% and 18% of the total numbers of individuals, respectively (Figure 4-18). A noteworthy result from this survey was the inclusion of an additional species sampled within the fishway, namely A. sclateri. This species was collected from pool 5 (the upper most pool surveyed) showing that two individuals were successfully able to negotiate the fishway under these hydraulic conditions (Figure 4-19). Bok et al. (2007) noted this species only able to negotiate drops between pools of up to 120 mm, but successful negotiation through the fishway meant that these individuals were able to overcome drops of 200 mm. It was noted that no juvenile fish were surveyed within the fishway. Utilising the numbers of species and individuals surveyed within the upper levels of pools as an indication of the successful passage of those species, again T. sparrmanii showed the greatest proportion of success, with 63% of the overall surveyed population being surveyed within the upper level of pool. Sixty percent of the Labeo capensis individuals were surveyed within the upper level of pools. Again, with T. sparrmanii being regarded as one of the weaker-swimming species within the system, the successful passage of this species can be regarded as indicative that the remaining species could also successfully negotiate the channel under these hydraulic conditions.

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4.8.3. Survey 3

The complete results of the fishway survey are presented in Table 4-8, which indicates species, total numbers, an indication of the size classes, and from which pools the fish were sampled. Figure 4-20 presents the proportions of fish species that made up the community of species sampled. It can be seen that L. capensis, B. hospes and T. sparrmanii were the only three species occupying the fishway at the time of the survey and all three species occurred in low numbers. Survey 3 resulted in only three species of fish, namely L. capensis, B. hospes and T. sparrmanii sampled within the fishway, and all were sampled within the lower level of pools (Figure 4-21).

The overall flow within the river was considered low and observations at the fishway at the time of the survey indicated that attraction flows at the entrance of the fishway were not sufficient to attract fish to the entrance of the fishway. The presence of these individuals within the fishway is regarded as purely fortuitous. No juvenile fish were surveyed within the fishway. Attraction flow to the fishway at low flow rates is regarded as a limitation to the functionality of the fishway. It should, however, be borne in mind that the fishway was not designed to cater for fish migrations under these low flow conditions as it is assumed that the fish communities within the system have a lesser requirement for longitudinal connectivity during this period as no active migrations occur. This is also a scenario where the economics of the construction of the fishway were weighed up against overall ecological functionality. These results are therefore not thought to be an accurate reflection of the overall intended functionality of the fishway.

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Table 4-7: Results of Survey 2 (25 April 2014) at the Blouputs fishway.

Pool 1 (Exit) (These pools were HYDRAULIC CONDITIONS: Pool 2 inaccessible due to Drop between pools: 200 mm Pool 3 secured metal grid Water velocity through slot: 1.864 m/s covers) Pool 4 Turbulence within pools: 113.5 watts/m3 Pool 5 Pool 6 Pool 7 Pool 8 Pool 9 Pool 10 Pool 11 Species Size range* Species Size range Species Size range Species Size range Species Size range Species Size range Species Size range (No.) (No.) (No.) (No.) (No.) (No.) (No.) TSPA(1) 45 LCAP(5) 250-300 LCAP(3) 175-225 LCAP(3) 280-325 TSPA(3) 60-65 MBRE(5) 55-65 BAEN(1) 315 BAEN(3) 210-225 MBRE(1) 55 0 0 CGAR(1) 235 BTRI(3) 55-65 CGAR(1) 300 ASCL(1) 135 TSPA(1) 55 PPHI(1) 55 PPHI(1) 55 Pool 17 (Entrance) Pool 16 Pool 15 Pool 14 Pool 13 Pool 12 LCAP(4) 300-325 BAEN(3) 295-315 Species Size range Species Size range Species Size range Species Size range Species Size range Species Size range MBRE(9) 50-65 (No.) (No.) (No.) (No.) (No.) (No.) BHOS(12) 60-70 TSPA(3) 65-75 ASCL(2) 130-135 LCAP(1) 295 LCAP(2) 230-265 PPHI(3) 40-55 BAEN(2) 235-300 BAEN(1) 325 TSPA(1) 65 MBRE(3) 45-55 BHOS(3) 50-65 PPHI(3) 50-55 BHOS(2) 55-60 MBRE(2) 45-55 PPHI(1) 55 PPHI(1) 45 BTRI(4) 55-75 CGAR(1) 320 * Size range provided as Total length (TL) to the nearest 5 mm.

Figure 4-19: The proportion of individuals of the fish species sampled during April 2014 within the fishway Figure 4-18: The proportion of fish species collected within the that were in the upper level of pools in relation to those fishway during April 2014. surveyed within the lower level of pools.

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Table 4-8: Results of Survey 3 (11 September 2014) at the Blouputs fishway.

Pool 1 (Exit) (These pools were HYDRAULIC CONDITIONS: Pool 2 inaccessible due to Drop between pools: 200 mm Pool 3 secured metal grid Water velocity through slot: 1.224 m/s covers) Pool 4 Turbulence within pools: 58.0 watts/m3 Pool 5 Pool 6 Pool 7 Pool 8 Pool 9 Pool 10 Pool 11 Species Size range* Species Size range Species Size range Species Size range Species Size range Species Size range Species Size range (No.) (No.) (No.) (No.) (No.) (No.) (No.) 0 0 0 0 0 0 0 0 0 0 0 0 Pool 17 (Entrance) Pool 16 Pool 15 Pool 14 Pool 13 Pool 12 Species Size range Species Size range Species Size range Species Size range Species Size range Species Size range LCAP(3) 290-315 (No.) (No.) (No.) (No.) (No.) (No.) TSPA(2) 60-65 0 0 0 0 BHOS(3) 55-65 * Size range provided as Total length (TL) to the nearest 5 mm.

Figure 4-21: The proportion of individuals of the fish species sampled during September 2014 within the Figure 4-20: The proportion of fish species sampled within the fishway that were in the upper level of pools in relation to fishway during September 2014. those surveyed within the lower level of pools.

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4.8.4. General observations of fishway functionality

The efficiency of the fishway was considered by examining the species and the morphometrics of those species that had reached the upper level of pools. Given the repetitious hydraulic parameters from one pool to the next, it is assumed that the presence of fish within the upper level of pools means that those individuals were able to successfully negotiate the fishway in entirety. It should be noted that it was not possible to sample all of the fish within each pool and that a small percentage of individuals eluded capture. This was especially true for the upper level of pools where water depth did not allow for electro-fishing and so only cast netting was employed as a collection technique. The intensity and technique of the sampling effort was considered sufficient though to collect a representative sample of the fish moving through the fishway.

One of the reasons why pool and weir fishway designs tend to lose functionality at low flows is that there is not enough water depth flowing over the weir that allows deep- bodied (compressiform) fish species to swim over (Bok et al., 2007; pers. obs.). This means that, under very low flow conditions, the fishway tends only to cater for species that can jump over the weirs within the fishway. The standard vertical slot design (with no sills) creates a continuous flow through the slot, which allows fish to navigate within the water column. This allows the vertical slot to cater for bottom-dwelling as well as top-dwelling species without creating the need for otherwise bottom-dwellers to jump. It was feared that placing a sill at the base of each slot opening within a vertical slot fishway would seemingly induce the conditions where bottom-dwelling species would be forced to the surface to cross between pools, which would reduce the functionality of the fishway. It should be noted that the vertical slot is 300 mm wide, which effectively concentrates the water through a relatively narrow area, creating a deeper volume for compressiform fish to utilise. The relatively deeper volume as the water flows over the weir and through the slot also means that enough cover is provided to bottom-dwelling species to swim between pools. The results from the fishway monitoring show A. sclateri (a bottom-dwelling species) as well as T. sparrmanii (a compressiform species) both successfully negotiating the channel under moderate flow conditions (Table 4-7). This is a positive sign regarding the overall functionality of the fishway and the success of the design modifications.

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Attraction flows is cited as one of the most prominent reasons for overall lack of functionality amongst fishways (Katopodis, 1992; Rajaratnam et al., 1992; Mallen- Cooper, 1996; Coax & Welcomme, 1998; Bok et al., 2007). It is well known that migrating fish will utilise the mainstream currents of the watercourse for navigation purposes, with the majority of species migrating within the peripheral zones of the mainstream currents to conserve swimming energy (Bok et al., 2007). It is earlier noted that the fishway at Blouputs is associated with the high crest weir. The main channel of the watercourse flows over the low crest weir, which is on the opposite bank of the river to the fishway. A strong current is also directed over a canoe ramp. This means that the main channel of the watercourse and the strongest flows and currents are not located near the fishway. Many of the fish seeking upstream migrations will try to traverse the weir within this area and may not find the entrance to the fishway, which is located at the periphery of an area of relatively low flows. An analysis of the flow rates of the river and the proportions of how much water flows over the low crest weir as opposed to the high crest weir was undertaken. The results showed that the higher the overall flow rates of the river, the smaller the ratio of flow over the low crest weir versus the flow over the high crest weir. This is presented in Figure 4-22.

It can be seen that as the overall river flow rate increases, the smaller the ratio between the volumes flowing over the high crest weir and the low crest weirs become. The difference in levels between the high crest and low crest is 300 mm. Water only begins to flow over the high crest weir as the river flow rate exceeds 14.87 m3/s. At lower flow rates the water is channelled only over the low crest weir (100% of the flow), but as the flow rate increases, the flow is increasingly dispersed along the entire width of the watercourse and the dominance of the flow volume over the low crest weir is lowered. This means that the dominance of the attraction flows at the low crest weir and the canoe ramp becomes less as the overall river flow rate increases. From this, the fishway will gain functionality as the flow rate in the river increases.

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Figure 4-22: Flow rate percentage ratio (left axis) between the high crest and low crest weir as the overall river flow rate increases (flow volume read off the right axis).

The results from survey 3 show the impacts of reduced attraction flows on fishway functionality. Visual observations taken at the time of the survey saw occurrences of jumping into the low crest weir, trying to traverse the weir. The time of the survey was not within an active migratory period and therefore these were sporadic occurrences. It did show, however, that individuals were attempting upstream migrations, and given that only three fish were collected within the fishway at the time, it could be concluded that the fish were not able to locate the entrance to the fishway. This is attributed to the lack of attraction flows at the time of the survey.

4.8.5. Data comparisons to similar studies

Fouché & Heath (2013) reported on extensive field monitoring and evaluations of a fishway located at the Xikundu Weir on the Luvuvhu River. The design of the Xikundu fishway is based on a notched pool and weir design, whereas the Blouputs fishway is based on the vertical slot design (with various modifications as mentioned previously). Although differing in basic design, the sills that were constructed in the base of the open slots in the Blouputs fishway makes for some similar hydraulic characteristics and therefore useful comparisons in functionality can be drawn. A comparison of some key design features is presented in Table 4-9Table 4-. Construction of the Xikundu was

212 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT completed in 2003 (Fouché & Heath, 2013), whereas Blouputs fishway was completed in late 2013 (pers. obs.). Therefore the design of Blouputs fishway allowed for the incorporation of “lessons learnt” from monitoring of previously-constructed fishways, analysis of potential shortcomings and degree of functionality.

Table 4-9: Comparisons of some key design features between Xikundu and Blouputs fishways.

Design feature Xikundu fishway Blouputs fishway Basic design Notched pool and weir Vertical slot Slope 1:10 1:11 Pool dimensions 1800 x 2400 mm 1800 x 1500 mm Height of sills between 600 mm 600 mm pools Width of slot 500 mm 300 mm Offset patterning (each successive slot opening Straight (aligned Baffle orientation is located opposite to the previous one) patterning) Number of pools 23 17 Resting pools at turning No Yes points

After extensive surveys, Fouché & Heath (2013) report that Xikundu fishway can be considered to be only partially functional due to the relatively small number of fish observed to have made routine use of the fishway. The limiting factor was assumed to be the turbulence within the pools, although the turbulence levels were reported to not have exceeded 70 watts/m3. This is below the limits recommended by Bok et al. (2007), of 150 watts/m3 for smaller fish species and 200 watts/m3 for larger fish species. It is also far below the turbulence levels that fish were able to negotiate within the experimental vertical slot fishway channel that was tested as part of this thesis (Chapter 2 and Chapter 3), which were shown to be as high as 620 watts/m3. Another hydraulic parameter considered limiting to successful fish passage is the water velocity through the slot (Blouputs) or flowing over the notch (Xikundu). Depending on the flow volumes of the river at the time of the surveys, reported water velocities were reported as between 1.224 m/s and 1.864 m/s, and 0.600 m/s and 1.815 m/s for Blouputs and Xikundu fishways, respectively. Initial surveys of the Blouputs fishway indicate that a relatively good diversity of fish species and size class range utilise the fishway. Relatively low numbers were observed during the times of the surveys, however. This was thought to be largely due to the timing of the surveys not coinciding with active migratory periods and therefore those individuals surveyed within the fishway were thought to be undertaking passive migrations, which are done on a far lesser scale. Another key feature that determines functionality of the fishway is the locality of the entrance as well as the associated attraction flows associated with the entrance. Xikundu fishway does not receive supplementary attraction flows and the entrance is 213 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT located in a relatively hydraulically quiet area. Blouputs fishway does make provision for supplementary attraction flows and the fishway entrance is located at the base of the weir, which makes it easier for fish to locate. From these preliminary findings, the vertical slot design at Blouputs is considered to be more ecologically functional than the notched pools and weir design at Xikundu, with the locality of the entrance and associated attraction flows being the factors considered to be the main factors leading to the limitation of functionality.

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4.9. CONCLUSIONS & LESSONS LEARNT

An analysis of the hydraulic characteristics of the Blouputs fishway was undertaken to determine how it would function hydraulically over a wide variety of flow conditions. The gauging structure is a standard calibrated structure and therefore flow volumes at the time of sampling are readily calculated. As the dimensions of the intake to the fishway (the fishway exit) are also known, the discharge rate through the fishway can also be readily calculated. As the discharge rate through the fishway can be calculated, all the associated internal hydraulic parameters of the fishway (difference in water levels between two successive pools, the velocity of the water through the slots, and the resulting turbulence levels within each pool) can also be calculated. Therefore, at the time of a survey, the hydraulic parameters are easily obtainable, and this information can be coupled to the biological components of the fishway. This was successfully undertaken during the evaluation of the functionality of this fishway within this chapter. Preliminary findings of the ecological functionality of the fishway at Blouputs indicate that this design, and the associated orientation of the exit, locality of the entrance and associated attraction flows, will enhance longitudinal connectivity of the river system at this site.

It is recommended that routine monitoring of this fishway be undertaken that incorporate a variety of hydraulic conditions. Monitoring should also include peak migratory periods when fish would be actively seeking upstream passage across the instream barrier. More favourable survey conditions (peak migratory periods and relatively higher flows) would allow for more comprehensive data to be gained that would improve the confidence in the data.

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4.10. REFERENCES

Benade, C. (1988). Episodic flood events in the Orange River System - an ecological perspective. Proceedings of Conference Floods in Perspective, Paper (3.6). Organizing Committee, Floods in Perspective - C.104, CSIR, Pretoria, South Africa. pp. 1-16. Benade, C. (1993). Studies on fish populations in the regulated Orange River system within the borders of the Cape Province. Unpublished M.Sc. Thesis, University of the Orange Free State, Bloemfontein, South Africa. p. 185. Benade, C., Seaman, M.T. and de Vries, C.P. (1995). Fishways in the Orange River system: Neusberg Weir fishway, Marksdrift Weir fishway and Douglas Weir fishway. In: Bok, A.H. (ed.). Proceedings of the fishway criteria workshop, D’Nyala Nature Reserve, Northern Province 2-5 May 1995. Water Research Commission and the Department of Water Affairs and Forestry, Pretoria, South Africa. Benade, B. (2003). The ecological importance and sensitivity of the Lower Orange River confluence. Lower Orange River management Study. Appendix 4. Draft Report. Task 8.3. Unpublished Report for Ninham Shad. Cape Town South Africa. Bok, A., Kotze, P., Heath, R. and Rossouw, J. (2007). Guidelines for the planning, design and operation of fishways in South Africa. WRC Report No. TT 287/07. Water Research Commission, Pretoria, South Africa. Chutter, F.M. (1973). An ecological account of the past and future of South African rivers. Newsletter of the Limnological Society of Southern Africa, 21: 22–34. Coax, I.G. and Welcomme, R.L. (1998). Rehabilitation of rivers for fish. European Inland Fisheries Advisory Commission of the United Nations Food and Agricultural Organization. London Fishing News Books, Blackwell Science. Oxford. p. 260. Dallas, H.F. (2007). River Health Programme: South African Scoring System (SASS) data interpretation guidelines. Institute of National Resource, Department of Water Affairs and Forestry, Pretoria, South Africa. DWAF (Department of Water Affairs and Forestry). (2002). Lower Orange Water management Area (LOWMA): Water Resources Situation Assessment. Report No. P14000/00/0101. Prepared by V3 Consulting Engineers. Department of Water Affairs, Pretoria, South Africa.

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DWA (Department of Water Affairs). (2012). Hydrological Services – data, dams, floods and flows. Department of Water Affairs, Pretoria, South Africa. Accessed September 2012 at URL: https//www.dwa.gov.za/hydrology. DWA (Department of Water Affairs). (2013). Development of reconciliation strategies for large bulk water supply systems Orange River: Surface water hydrology and system analysis report. Report No. P RSA D000/00/18312/7. Prepared by WRP Consulting Engineers Aurecon, Golder Associates Africa, and Zitholele Consulting. Department of Water Affairs, Pretoria, South Africa. Department of Information. (1971). Taming a River Giant. Dag Breek (H & G) Johannesburg, South Africa. Earle, A., Malzbender, D., Turton, A. and Manzungu, E. (2005). A Preliminary basin Profile of the Orange/Senqu River. INWENT Capacity Development Programme in cooperation with the African Water Issues Research Unit, CIPS, University of Pretoria, in support to the SADC Water Division and ORASECOM. p. 40. Fouché, P.S.O. (2009). Aspects of the ecology and biology of the Lowveld largescale yellowfish (Labeobarbus marequensis, Smith, 1843) in the Luvuvhu River, Limpopo River System, South Africa. Unpublished Ph.D. Thesis. University of Limpopo, Polokwane, South Africa. Fouché, P.S.O. and Heath, R.G. (2013). Functionality evaluations of the Xikundu Fishway, Luvuvhu River, South Africa. African Journal of Aquatic Science, 38 (suppl.): 69-84.

Golder Associates Africa. (2008). Fish species specifications for fish ladders associated with the proposed construction of 2 DWAF gauging weirs in the Orange River. Report No. 11589-6085-2. Golder Associates Africa, Johannesburg, South Africa. Jubb, R.A. and Farquarson, F.L. (1965). The fresh water fishes of the Orange River drainage basin. South African Journal of Science, 61: 118-125. Jubb, R.A. (1967). Freshwater Fishes of Southern Africa. A.A. Balkema, Cape Town, South Africa. p. 248. Katopodis C. (1992). Introduction to fishway design. Unpublished working document. Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, Canada. p. 62. Kleynhans, C.J. (2007). River ecoclassification: manual for ecostatus determination (Version 2). Module D: Volume 1 Fish Response Assessment Index (FRAI). WRC Report No. TT330/08. Water Research Commission, Pretoria, South Africa. Kleynhans, C.J., Louw, M.D. and Moolman, J. (2007). Reference frequency of occurrence of fish species in South Africa. WRC Report No. TT331/08. Department of water Affairs and Forestry (Resource Quality Services) and the Water Research Commission, Pretoria, South Africa. 217 | P a g e CHAPTER 4: CASE STUDIES & LESSONS LEARNT

Kriel, J.P. (1972). The role of the Hendrik Verwoerd Dam in the Orange River Project. The Civil Engineer in South Africa, 14(2): 51-61. Mallen-Cooper, M. (1996). Fishways and freshwater fish migration in south-eastern Australia. Unpublished Ph.D. Thesis. University of Technology, Sydney, Australia. p. 377. Mucina, L. and Rutherford, M.C. (2006). The Vegetation of South Africa, Lesotho and Swaziland, Strelitzia 19. South African National Biodiversity Institute, Pretoria, South Africa. Rajaratnam, N., Katopodis, C. and Solanki, S. (1992). New designs for vertical slot fishways. Canadian Journal of Civil Engineering, 19: 402-414. Ramollo, P.P. (2010). A review of the freshwater ecosystems of the Northern Cape Province. Report No. 58. Northern Cape Department of Environment and Nature Conservation, Kimberley, South Africa. Ramollo, P.P. (2011). Freshwater Fish Abundance and Distribution in the Orange River, South Africa. Journal of Fisheries International, 6(1): 13-17. Scott, L.E.P., Skelton, P.H., Booth, A.J., Verheust, L., Harris, R. and Dooley, J. (2006). Atlas of Southern African Freshwater Fishes, Smithiana, Monograph 2. The South African Institute for Aquatic Biodiversity, Grahamstown, South Africa. p. 303. Skelton, P.H. (2001). A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa. p. 395. Skelton, P.H. and Cambray, J.A. (1981). The freshwater fishes of the middle and lower Orange River. Koedoe, 24: 51-66. Tomasson, T. (1983). The biology and management considerations of abundant large cyprinids in Lake le Roux, Orange River, South Africa. Unpublished Ph.D. Thesis. Rhodes University, Grahamstown, South Africa. Tomasson, T. and Allanson, B.R. (1983). Effects of hydraulic manipulations on fish stocks. In: Allanson, B.R. and Jackson, P.B.N. (eds.). Limnology and fisheries potential of lake le Roux. South African National Scientific Programmes Report No. 77. Cooperative Scientific Programmes CSIR, Pretoria, South Africa. pp. 122-131. Tooth, S. and McCarthy, T.S. (2004). Anabranching in mixed bedrock-alluvial rivers: The example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa. Geomorphology, 57: 235-262. Wellington, J.H. (1933). The middle course of the Orange River. South African Geographical Journal, 16: 58-68. Wellington, J.H. (1958). The evolution of the Orange River basin: some outstanding problems. South African Geographical Journal, 40: 3-30. 218 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

DETERMINING THE BIOLOGICAL REQUIREMENTS OF SELECTED IMPORTANT

MIGRATORY FISH SPECIES TO AID IN THE DESIGN OF FISHWAYS IN SOUTH

AFRICA

CHAPTER 5: General Conclusions and Recommendations

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5.1. CONCLUSIONS

The main research question of this thesis and therefore the central theme was:

A further research question is also included:

The design of one generic fishway to suit the needs of all species has been met with limited success, with early studies indicating that it is neither feasible nor ecologically sound (Schwalme et al., 1985). It has been suggested by these authors that a combination of various fishway designs would be necessary to cater for the migration needs of all species within a given riverine system. Using a combination of standard fishway designs and concepts has been met with success at many sites throughout South Africa. Where site and river hydraulic conditions allow for it, combinations of pre-barrage pool and weir designs, to gain height before the placement of a standard vertical slot fishway, has shown to be successful. Combining a vertical slot fishway with a sloping weir that provides a wet roughened surface also has been shown to be successful, especially with coastal fishways. Exploration of designing a “double vertical slot” fishway was undertaken as part of this study in an effort to establish a generic fishway model that could cater for a wider diversity of fish species and size classes. A summary of this study (Rossouw et al., 2007) is provided in Chapter 2, where a scale model was tested at the DWS Hydrometric Laboratory in Pretoria, South Africa. Although this design was considered theoretically feasible, it was not considered

220 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS practical at the full scale due to it being too intricate to construct. It was also thought to not be able to withstand the vigour of floodwaters and associated floating debris, and therefore this concept has since been abandoned. What this design concept did achieve, however, is to induce progressive and innovative thinking to develop better- functioning fishways, and laid the foundation for a more progressive interdisciplinary cooperation between engineers and biologists. The ultimate aim of the experimentation was to assist in the planning, designing and construction of economical, yet effective, fishway channels. An ecologically sound yet cost effective fishway would allow for a higher number of fishways to be constructed within river systems throughout the country where budget constraints are regarded as a major inhibitory factor to fishway construction. If implemented, this will subsequently enhance the overall conservation of all fish species throughout the country.

Habitat fragmentation is regarded as one of the most profound impacting features responsible for the decline of fish numbers and diversity worldwide. Fishways have been shown to effectively ameliorate these impacts. Functionality of fishways has grown over the years with a greater understanding of hydraulic principles and extrapolation of these principles to develop effective fishway designs. Together with a growing understanding of how fish are able to interact with these hydraulic variables, it is believed that fishways can provide a successful means to mitigate habitat fragmentation brought about through the construction of migratory barriers along river systems and that this will ultimately enhance the conservation of fish diversity and numbers worldwide. The implementation of fishways to enhance migratory freedom within rivers throughout South Africa is a growing trend. As each river system is different, each supporting a different species community structure that has varying migratory requirements and limitations to what hydraulic conditions they can accommodate, further research is required to refine the design of fishways aimed at specific localities. This study has shown that a vertical slot, with design modifications that have actually simplified the design and construction process, is able to effectively allow freedom of passage across migratory barriers to a wide diversity of fish species.

In conclusion, mitigating the impacts of instream migratory barriers for maintaining longitudinal connectivity of a river system with the specific aim of preserving the overall productivity and vigour of a fish community can only be partially successful through the provision of fishways. Deteriorating water quality is a major perpetual driver of ecological transformation of river systems that is leading to lowered health and vigour 221 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS of fish communities. When talking of fish being primed at the onset of the summer cycle to undertake en masse spawning migrations, it needs to be considered that only healthy individuals within a community would breed to full potential. Poor water quality that leads to organ deterioration and parasite infestations within the fish would lower the fecundity and, ultimately, reduce the overall vigour of the population. Habitat degradation and transformation is another major driver of ecological transformation. Fish (and other migratory aquatic biota) undertake migrations to exploit alternative habitats, with suitable spawning beds perhaps being the most well-known. If the ultimate destination of the migrating fish (in this case, the spawning beds) are degraded and rendered unsuitable, then the provision of fishways to promote access to these areas is considered futile. Making provision for fishways at migratory barriers is therefore only one focal area of consideration within an integrated and holistic approach to aquatic resource conservation.

This study undertook to test the viability of implementing a vertical slot fishway at relatively steeper gradients using a scale model. This was done by testing the success rates of various fish species under a series of gradients and flow conditions, under both field and controlled laboratory conditions. The specific focus was on determining the upper limits of the hydraulic parameters that could be overcome by a diversity of fish species when negotiating a fishway channel. The experiments utilised two different communities of fish, namely from the Sabie River (Lowveld region) and Vaal River (Highveld region) systems. The study aimed to provide a better understanding of the hydraulic parameters to aid in the design specifications of fishways that would be applicable to various communities of fish species. The target of the study was to ultimately increase the ecological functionality and performance of fishways within South Africa.

Chapter 1 introduced the concept of fishways, various designs and the international trends of design implementation through the ages. Fishways in the South African context and the development of fishway implementation and design was also explored through literature surveys, personal communications with professionals that were responsible for design of the fishways and follow up surveys. Through a survey of international fishway literature and trends in fishway designs, it was concluded that South Africa remains an emerging authority on the subject, and does not offer the advancements in design, monitoring and implementation of fishways as those located throughout Australasia, America and Europe. This is largely been due to lack of 222 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS expertise, limited funding and a general lack motivation to drive the concept due to a lack of understanding of the importance of the concepts in holistic river conservation. There is, however, a changing general trend toward greater awareness of the importance of fishways and the overall health of an aquatic system. This is from both the biological and engineering sectors. In an attempt to create a database of the fishways throughout South Africa, it was found that information and data are limited. It was difficult to verify localities and the status of functionality of the fishways. Many fishways are located on private property, making access for verification of design type, degree of functionality or even their existence difficult. Many fishways were also constructed by private individuals, with no official records or specialist studies having been undertaken. Many references to fishways were based on a fleeting mention by third parties, which also hampered verification. A list of fishways known throughout South Africa, their locality, design, and notes on functionality has been provided, but with the limitations of unequivocal verification.

The experiments where a group of fish were exposed to varying gradients and flow conditions of the vertical slot scale fishway model under controlled conditions within the laboratory (Chapter 2) showed that the particular design of fishway was capable of passing a community of fish species of varying size classes at a gradient at steep as 1:3 with relatively good success. Three gradients of the channel were tested, namely 1:3, 1:4 and 1:5 at various discharge rates. Although fish were able to successfully negotiate the channel at the steeper gradient of 1:3, the overall functionality was improved when the gradient was lowered toward 1:5. This was common for the vast majority of the test species used for the experiments. Flow rate (discharge) was also found to be important in the functionality of the fishway channel. Fishway channels tend toward optimal hydraulic conditions when discharge rates satisfy submerged flow conditions. It is thought that under these conditions that the greatest proportion of fish would be able to successfully negotiate the channel. From the laboratory experiments it was shown that, at the moderate channel gradient of 1:5, a large proportion of the test population were able to successfully negotiate the channel as flow rates reached as little as 25% of the quantity required to satisfy submerged flow conditions if a sill was placed within the bottom of the slot that ensured a minimum water volume within each pool. There was little increase in success rates throughout all the species of fish utilised for the testing with further increases in flow rate. This concept becomes applicable when designing a fishway according to the natural hydrological regimes of a river system. Due to budgetary constraints and practicality of design and construction, most fishways are designed to function optimally only for a set period during the 223 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS season. This period coincides with the times that the fish populations are in greatest need for freedom of movement (e.g. spawning periods). The fact that a vertical slot fishway can be considered successful at as little 25% of the quantity required for submerged flow conditions means that the fishway would function over an extended period and not limited to only a small portion of the season. Most developers and engineers shied away from projects where the provision of mitigation measures was shown to be more costly than the project itself, regardless of the ecological benefits. As providing mitigation to abate the impacts to river fragmentation is statutory under South African environmental legislation, inhibitory costs of a fishway have often led to a compromise in overall functionality of the fishway to allow for a more economically viable development, and most often it is the period of functionality that is compromised on. Seasonal variation, common to the vast majority of river systems throughout southern Africa, means that river systems are subject to a large variation in seasonal flow volumes, often ranging from extremes of zero flows through to flood conditions. In such cases, the usual decision support scenario is to identify key obligatory migratory species within the system in question (normally those species that undertake seasonal migrations for breeding purposes or to complete a stage of their life cycle) and the maximum functionality of the fishway is guaranteed only for these key periods. The remainder of the time, the functionality of the development infrastructure takes precedence, which is often the case under low flow conditions.

Although an integral part of designing and testing the efficiency of a fishway channel, laboratory experimentation was found to have limitations. This is because it relies on inducing a forced response swimming behaviour rather than inducing a voluntary swimming response. It was seen that a forced swimming response was notably less vigorous than swimming behaviours under natural conditions. The swimming responses of the various individuals were found to be erratic throughout all phases of the experimental procedures. Even though experiments were repeatedly done, a relatively high standard deviation within the experimental data was noted and no explanation could be offered as to why individual fish successfully negotiated passage during one experiment and then were reluctant to negotiate the channel under the same flow conditions during a repeat of the same experiment. This aspect has been identified as a limitation in other laboratory-based studies (Bunt, 2001; Peake, 2004). This is attributed to be a consequence of the fish being housed within an artificial system that are not subject to natural migratory cues that they would otherwise be exposed to within a natural river system. If the data provided by these laboratory experiments are extrapolated to provide the hydraulic parameters for a fishway design 224 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS on a given river system, it is thought that the fish within the natural system would have little difficulty in successfully negotiating the fishway. The data gathered through these laboratory experiments have already shown that the test species are capable of negotiating more difficult hydraulic conditions than previously thought. Although fish within natural river systems that are exposed to natural migratory cues have been shown to exhibit higher swimming vigour, it is recommended that these defining parameters be utilised as the upper limit when designing for the hydraulic limits imposed by a fishway. This would allow for a level of safeguarding against imposing hydraulic conditions that are indeed limiting to passing fish. Remaining within these conservative parameters, when designing a fishway for a barrier on a river system is thought prudent and will provide for an ecologically sound and functional fishway channel.

The vertical slot fishway test scale model used for the laboratory experiments described in Chapter 2 was transported to various localities at rivers within South Africa to test the viability of the channel under field conditions, which are described in Chapter 3. Where opportunity provided for placing the channel directly within the watercourse at the base of a migratory barrier during periods of active migrations of the fish, it was found that various species were able to negotiate gradients as steep as 1:3.15. It was found, however, that a channel gradient of 1:5 allowed for the greatest number of the widest diversity of species to pass the barrier indicating that a fishway of a similar design and dimension should not be implemented at a gradient greater than 1:5. Those species that were successful in negotiating the experimental fishway channel at these steeper gradients generally represented the stronger-swimming species of the river systems. For broad ecological functionality, a fishway needs to be designed to cater for the weakest-swimming species within a given system that includes a diversity of fish species (Pon, 2008). Therefore the inclusion of resting pools in all fishways, excepting the relatively short ones, should be considered mandatory to allow the best advantage to the weaker-swimming species of the system. Field experimentation (Chapter 3) did reiterate the findings of the laboratory experiments (Chapter 2), and was able to successfully increase the knowledge base of the migratory needs and limitations of a greater diversity of fish species within South Africa.

The findings of the field-based experiments reiterated the shortfalls of trying to gain repeatable results from induced behavioural responses from a test population, as identified from the results gained from Chapter 2. Based on the findings of the 225 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS laboratory testing and the field testing of the experimental vertical slot fishway channel, the vast majority of fish species utilised for the experiments were shown to successfully negotiate the channel in acceptable numbers at a channel gradient of 1:5. It is recommended, however, that a conservative approach be adopted and that a channel gradient of 1:10 be regarded as the upper limit of the gradient of a vertical slot fishway.

From observations taken during the field experimentation, as well as general observations taken during field surveys, it is assumed that the key environmental cue to induce active migrations of the fish communities within the river is increased flow throughout the system as this was the major environmental change observed. Increased flow volume increases habitat availability by opening up side channels, so there is a greater opportunity for fish to seek favourable hydraulic conditions and many instream obstacles (natural or artificial) that inhibit migrations at low flow are drowned out if the river flow rate increases sufficiently. Therefore, physically, the habitat presents greater opportunity for colonisation with increased flow volumes. There are associated environmental factors coupled to the rainfall event that are presumably synergistic in inducing migration behaviour. Rainwater and the associated runoff surface water that enters the system will influence the water quality, temperature and the increased turbulence will mobilise sediments within the system that will increase turbidity levels. Surface water runoff also transports sediments to the watercourse, which would also increase the turbidity of the system. It is postulated that this also contributes to the success of migrational movements of fish. Many of the fish species that undertake active migrations are vulnerable to predation and leaving the refuge of cover to undertake the migrations exposes individuals to predators. Increased turbidity within the system increases natural cover, adding a degree of safety to those individuals, which adds to the ultimate success of migrational activities. In a summer rainfall region, rainfall periods coincide with increased photoperiod, and increasing ambient temperature that increase water temperatures. Fish are poikilothermic organisms, with their body temperature being largely governed by the surrounding water temperatures. Metabolic rate of these organisms increases with an increase in body temperature (Schmidt-Nielsen, 1998) and this is coupled to an increase in activity levels. An increase in temperature and intensity of sunlight coupled to the onset of the summer cycle increases the overall productivity of a river system (Davies & Day, 1998). This increases the nutrient availability for fish communities, which improves the physical condition of the fish. This enhanced conditioning of the fish would be in preparation for breeding, and increased flows within the river is then considered to trigger the active migration behaviour of the fish that are in good physical condition. 226 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

This is a complex interplay of environmental, physical and biological factors that are difficult to simulate under laboratory conditions.

Favourable circumstances during the testing period of the scale fishway meant that the accumulation of knowledge gained throughout the project allowed for the input into the design and implementation of a full-scale fishway (Chapter 4). The Department of Water and Sanitation (DWS) was in the process of designing a flow-gauging weir on the Orange River at Blouputs, located downstream of Augrabies Falls in the Northern Cape Province. This provided the opportunity to implement the knowledge gained from the project to design a fishway to mitigate the impacts of establishing an instream migratory barrier within the system at the site. This fishway was monitored on three separate occasions, under different hydraulic condition, in order to determine if it could be considered ecologically functional. Results gained during the monitoring were regarded as limited due to the monitoring periods not coinciding with active migratory periods. The results did indicate, however, that both juvenile and adult fish of a diversity of fish species ranging from weaker-swimming species to stronger-swimming species were able to successfully negotiate the fishway. The process of design and implementation of this fishway is also considered a successful and progressive association between design engineers and biologists.

5.2. IMPLEMENTATION OF FISHWAYS TO MITIGATE CURRENT AND EMERGING MAJOR

THREATS TO NATURAL FISH PASSAGE IN SOUTH AFRICAN RIVERS

5.2.1. Hydropower developments

Hydropower schemes are becoming an increasingly popular means of alternate renewable electricity generation from both the private and public sectors. The vast majority of the hydropower schemes owned by government or by ESKOM (the current national electricity supplier throughout South Africa) are constructed within the dam walls of large impoundments (e.g. Vanderkloof Dam, Gariep Dam, Sterkfontein Dam), whereas the hydropower schemes belonging to the private sector are mostly run-of- river developments. Run-of-river hydropower developments make use of a natural steep gradient or natural feature along a watercourse that offers a large head difference over a relatively short distance. This type of development does not require the construction of substantial impoundment structures to create the head difference. These types of schemes are typically cheaper to construct. Where these 227 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS developments cannot take advantage of natural topographical features (e.g. waterfalls), they require the construction of instream barriers (impoundments) to provide sufficient head difference that will provide sufficient kinetic energy to drive the turbines. These impounding structures can be anything from two metres up to 40 m in height (pers. obs.). Hydropower schemes are relatively expensive to develop, which means that developers seek the maximum head difference in order to deliver the greatest possible amount of kinetic energy from the flowing water to make the development economically viable. This means that the maximum allowable height of the required barrier is also sought, and the higher the barrier, the more difficult and expensive it is to mitigate the impacts to migratory barrier formation. Hydropower schemes function on the basis that the greater volume of water that can be passed through the electricity-generating turbines, the greater the potential for generation capacity. The developers of hydropower schemes would therefore opt for the greater proportion of river flow volume to service the scheme rather than being allowed to maintain ecosystem functionality (to satisfy ecological flow requirements). Under high flow or flood conditions, this aspect is largely inconsequential as ecological flow requirements are generally satisfied during these periods. It is under lower flow conditions that management of the scheme becomes pertinent. Current environmental legislation requires that provision for a minimal base flow within rivers be maintained for ecological maintenance (ecological flow requirements) to the effect that ecological maintenance, including providing adequate flows through fishways to maintain functionality, takes precedence over servicing of the hydropower scheme. This often means that hydropower schemes shut down at lower flows, which has obvious socio-economic impacts. Improving the overall performance of fishways will aid in balancing the flow volume demands, as a fishway that requires relatively lower flow volumes to function optimally will be obviously beneficial to developments. The results of this study did aid in improving the functionality of fishways at lower flow rates.

5.2.2. Flow-gauging weirs

Flow-gauging weirs also constitute a large proportion of the migratory barriers along river systems throughout the country. The overall accuracy of flow measurement is an important component of these structures and therefore external influence or interferences by diverting partial flows through a fishway was frowned upon. With a greater understanding of flow dynamics of fishways, and the influence on fishway functionality, the functionality of these flow-gauging structures would not be compromised, as a corrective factor could always be implemented when calculating

228 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS flows. To date, it has been considered best practice to prioritise flow through the fishway within seasonal river systems, meaning that the fishway would be supplied with water before any water crests the weir. It was found, however, that this very often has led to debris being drawn into the fishway, which compromised its functionality. More recently, by allowing the water to crest the weir first and reducing the draw-in of water into the fishway, the influx of debris can be reduced, which effectively lowers the need for routine maintenance. This is thought to be effective on regulated perennial rivers. Non-perennial rivers that incorporate fishways should ensure that the first flows of surface water be prioritised through the fishway. Debris deflectors can be used to divert debris that would otherwise be drawn into the fishway, especially as debris load is high with the onset of surface flows within these rivers. Fish will, however, utilise the onset of the surface flows to quickly exploit the expanding available habitat, and also would utilise these river types for seasonal breeding. To have these channels open to longitudinal migrations from the onset of the first surface water flows would mean that fish would have the maximum opportunity to utilise this habitat whose availability limited to times of seasonality. It is therefore recommended that, under these conditions that debris deflectors be used and that a balance be reached between regular maintenance of the fishway and ecological functionality from the onset of the first flows of the river. Another recommendation in terms of hydraulic functionality of fishways coupled to seasonality is that a fishway should be constructed to not only be able to withstand river flood conditions, it should be designed to allow for seasonal flooding under exceptionally high flow conditions. Flood conditions carry a large debris load that travels with a high kinetic energy. Large debris, such as large tree trunks and branches, could damage the fishway infrastructure if not constructed to withstand these impacts. Very often this debris gets caught up in the fishway, which would impact the hydraulic functionality of the fishway. Routine maintenance of fishways is very often neglected and so the only way that this debris could be removed from a fishway is for the entire system to overtop. This is also true to floating aquatic vegetation. It is not uncommon for the exotic water hyacinth (Eichhornia crassipes) to grow abundantly within a fishway, effectively rendering it ineffective. Flooding of the fishway by overtopping would remove this, together with other floating debris. Flooding of a vertical slot fish can be avoided by constructing the walls high enough so that the slot opening can accommodate the rise in water levels under flood conditions. It is known, however, that fish tend to take refuge under flood conditions with very limited movement taking place, resuming migratory movements as the flood waters recede. The added expenditure of constructing a very deep fishway would therefore be regarded as being redundant. As mentioned, it is also regarded as beneficial for the maintenance of a fishway to allow overtopping during flood conditions. 229 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

5.3. RECOMMENDATIONS AND FACTORS TO CONSIDER FOR OPTIMAL FISHWAY

DESIGN

5.3.1. Economic considerations that influence design

Government funded projects where river barriers were to be constructed (e.g. gauging weirs) tend to allocate proportionately larger budgets to the provision of fishways, which allows for greater flexibility in designing fishways with greater functionality. Where it is established that a fishway is not feasible (e.g. high dam walls such as the recently completed De Hoop Dam on the Olifants River), the developers can be granted an exemption from providing for a fishway through authorisation of DWS and DEA (Department of Environmental Affairs). It is given, however, that where a fishway is deemed feasible, that is has to be provided for. This means that an important factor to be considered in designing a fishway is the overall costs of the construction and operations of a fishway. Factors that influence the overall cost of a fishway include the overall practicality of the design, implementation and construction and, primarily, ecological functionality during key periods of migrational activity of aquatic species (both fish and aquatic macro-invertebrates). By implication, the shorter a fishway is required to be, the more economical it would be to construct. This would, however, necessitate a relatively steeper gradient to overcome a migratory barrier of a given height. It therefore needed to be ascertained whether relatively steeper fishway channels (with their associated hydraulic parameters of water velocities, turbulence levels and height differences between successive pools) could still mitigate successful passage of an acceptable proportion of a fish population across an instream barrier within a given system without expending excessive energy reserves. Chapter 2 looked at exposing a community of fish species from the Vaal River system to a vertical slot scale model at relatively steeper gradients under varying hydraulic conditions, under controlled laboratory conditions. In doing so it was found that an acceptable proportion of individuals from all of the fish species utilised for the testing were able to successfully negotiate the vertical slot channel at a gradient of 1:5, with many being able to successfully negotiate the channel at a gradient of 1:3. These results indicate that a vertical slot channel at a gradient of 1:5 would successfully allow passage of the vast majority of individuals of all the species that are present within the Vaal River system. It should be noted, however, that the experimental fishway channel was relatively short, and therefore no resting areas were necessary, nor provided for. The relatively short channel allowed fish to negotiate the channel without the need for a

230 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS resting area and it was assumed that the fish did not suffer undue fatigue in negotiating the entire length of the channel.

5.3.2. Biological considerations that influence design

Migratory fish and invertebrate species, e.g. eels (Anguilla spp.) and freshwater prawns (Macrobrachium spp.) that occur in the Sabie River were not considered in this study. It is postulated that a boulder/rock substrate within a low-gradient (1:10) vertical slot fishway would allow for successful passage of these taxa. Eels usually utilise their climbing ability to ascend barriers rather than swimming abilities (Stuart & Mallen- Cooper, 1999; Bok et al., 2007) and therefore roughened wet surfaces along the peripheral zones of the watercourses provides better opportunity for passage. The upstream migrations of Anguilla spp. within coastal rivers along the east coast of southern Africa are undertaken during juvenile life stages (Skelton, 2001) and therefore have a relatively weak swimming ability. It is assumed that physical and hydraulic conditions that would cater for juvenile eels would also enable successful passage of invertebrate species that also require upstream passage across barriers. The standard vertical slot does not cater for these specific conditions as the slot openings between successive pools is a vertical surface, and provision for wetted surfaces or areas of gradual decline is made. Placing a rocky or pebble substrate within the bottom of the channel will enhance passage of these taxa through the pools, but passage through the slot openings where water velocity is at its maximum within the fishway would remain a limiting factor. Combining fishway types under these special circumstances e.g. a sloping weir and vertical slot as a fishway has been suggested. Careful consideration has to be made, however, for the cyclic hydraulic variation of the river system and how this affects the hydraulic functionality of the fishway. The time period of ideal hydraulic functionality then has to coincide with the seasonality of the migrations of the target species.

5.3.3. Design guidelines and considerations

Prior to designing a formal fishway structure, it needs to be established that a fishway is in fact necessary at the site. Bok et al. (2007) outlined the fishway necessity protocol, which is a useful tool to evaluate whether a fishway is required at a site. Reasons such as close proximity to a natural migratory barrier (e.g. waterfall), or potentially opening up of the watercourse to undesirable alien species, lack of suitable habitat upstream, etc. The following recommendations for fishway design are based 231 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS on the pretence that it has been established that a fishway is in fact necessary at a particular barrier and that it is both technically and economically viable to incorporate a fishway into the design of the barrier structure. Bok et al. (2007) also recommend that the accommodation of a natural bypass channel be explored as a first resort, and that a formal structure only be considered if a natural bypass channel cannot be accommodated. A natural bypass channel that simulates the natural river conditions and that has a substrate that simulates the river itself is thought to remain the most versatile and successful means of passing fish across a barrier and therefore it is reiterated here that this option should be initially explored. It has been found, however, that site conditions or the requirements of the barrier structure very often do not allow this option and therefore a formal fishway structure has largely become standard practice in ameliorating the impacts of migratory barrier formation.

5.3.3.1. Length of channel

The height of the barrier to be overcome needs to be taken into consideration when determining the design of fishway as well as the length of that fishway channel. Technical parameters of the design of the instream barrier infrastructure and local site conditions (natural rock substrates, rock ramps, natural geological features that could be utilised and/or incorporated into the fishway design) also have to be taken into consideration. It is recommended that the difference in water level between pools not exceed 0.2 m. If the pools are generally 2 m long, then it can be calculated that for every 0.2 m gained in height, a channel of 2 m is required (i.e. a barrier of 5 m in height would require 25 pools, which equates to a fishway channel of 50 m in length.

5.3.3.2. Resting areas

It has been suggested that resting pools be incorporated into the design of the vertical slot fishway to aid in allowing fish to recuperate from the physical exertion of negotiating difficult turbulence and velocity levels as well as to provide an overnight resting area for diurnal species that are undertaking upstream migrations. It has been further suggested that such species would retreat from the fishway to overnight in quieter waters to attempt upstream passage during daylight hours. Extensive field surveys undertaken by White et al. (2011) of a vertical slot fishway of 39 successive pools that incorporated two substantially larger resting pools indicated that fish showed no preference to overnighting in these resting pools. Further studies by Laine (1990) indicated that the migration process of fish through the fishway can actually be

232 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS interrupted by the provision of such resting pools, making the provision thereof counter- productive. It was concluded in that study that it may be advantageous to some species to limit the range of hydraulic parameters within a fishway by providing repetitious flow patterns, and that providing a standard vertical slot fishway with extensive resting pools substantially increases the design and construction costs and also “overly-complicates” the design, making for an arduous construction process. From those studies it could be seen that the cost-benefit ratio of providing resting pools was not considered viable and there seemed to be no justification in including resting pools within a fishway channel.

It was found, however, during the present study that standard practice for channelled fishway designs (vertical slot, pool and weir, etc.) is to incorporate a turning point in order to site the entrance of the fishway where it can be provided within the most optimal attraction flows. This is a turbulent area that is usually at the base of the barrier structure. This means that the fishway channel has to turn back on itself (i.e. have a turning point) in order for the entrance to be sited at the base of the barrier structure. The turning point has to incorporate a pool that is of a different dimension to the proceeding and preceding pools as the localities of the inflow and outflow have to be orientated differently to the rest of the pools. Normally, the inflow and the outflow would be located on opposite ends of the pool, but within the turning point pool, this orientation has to accommodate the angle of the turn. The turbulence levels within each pool of a vertical slot fishway channel, especially at steeper gradients of greater than 1:10, also has a carry-over effect of turbulence from the previous pool as not all of the turbulence is dissipated within the previous pool. This carry-over effect of the turbulence gains momentum as the water flows through the fishway and the flowing water is subject to an increasing resistance to flow, with the effect that each successive pool gets progressively deeper. This means that the channel eventually overtops if the sides of the vertical slot channel are not constructed deep enough to accommodate this. Constructing a larger pool roughly after every nine to ten pools effectively dissipates the carry-over turbulence, effectively negating this effect. The provision of larger resting pools therefore provide a three-fold function to the fishway: 1) provide a resting area for fish that are negotiating passage through the fishway channel; 2) provide a turning point for a channel that has to consider the siting of the entrance of the fishway to exploit attraction flows; and 3) dissipates latent turbulence levels carried over from previous pools. Making provision for larger resting pools approximately every eight to ten pools therefore remains a recommendation in fishway channels that are longer than eight to ten pools in length. This perspective is reiterated by Pon 233 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

(2008), who considered the inclusion of resting pools in all fishways, excepting the relatively short ones, as mandatory.

5.3.3.3. Setting maximum hydraulic parameters

It should be noted that the experimental channel was relatively short and the design parameters meant that an overall height difference of only 0.8 m at a slope of 1:5 (20%) could be accomplished, with eight slots over a channel length of 4.8 m. The fish were therefore required to negotiate the hydraulic conditions within the experimental channel for only a short period of time. Migratory barriers that require fishways are considerably higher than this and therefore will be exposed to the hydraulic conditions for a longer period of time (often requiring 20 to 25 pools). It is therefore prudent when designing a fishway that the maximum hydraulic parameters stay well within the capabilities of the weakest swimming species in order to prevent excessive fatigue and energy expenditure, and that a channel gradient of 1:10 be regarded as the upper limit of the gradient of a vertical slot fishway.

Turbulence levels within the pools that were successfully negotiated by the vast majority of test individuals ranged between 80 watts/m3 and 620 watts/m3. This wide range suggests that perhaps the level of turbulence is not necessarily a main limiting factor to fish utilising the fishway. This is because the calculation of turbulence within a pool is based on the overall theoretical average. In reality, this is not the case as the pool experiences high levels of turbulence in some areas and low levels of turbulence within others, depending on position within the pool and fish are able to avoid these areas of high turbulence levels. Limiting factors would be the critical points that fish would have to overcome in order to negotiate the channel. These include the velocity of the water as it flows between successive pools, which is a function of the change in water levels between successive pools and therefore a maximum drop between pools is recommended (see Table 5-1).

Table 5-1: Proposed design specifications and limitations for vertical slot fishways.

Inland vertical slot fishway Aspect Limit Recommended Maximum (steepest) gradient 1:10 1:10 Slot width 0.15 m 0.30 m Maximum drop between pools 0.20 m 0.15-0.20 m Maximum turbulence levels within each pool 500 watts/m3 <300 watts/m3 Maximum water velocity through slot 2.0 m/s <1.7-1.9 m/s

234 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

5.3.3.4. Fishway channel dimensions

The experimental vertical slot fishway channel was considered a small-scale model, aimed at allowing passage of only relatively small fish. The general recommendations of the size of a vertical slot fishway is that the pool length should be three times the length of the largest expected individual to use the fishway (Bok et al., 2007). The experimental channel had pool lengths of 500 mm, meaning that the largest fish that it could theoretically cater for should not exceed 167 mm TL. Both the laboratory and field testing showed that individuals as big as 330 mm TL could repeatedly successfully negotiate the fishway. It is not recommended that a fishway as small as the experimental design be utilised unless the target species and individuals are limited to small body sizes. The limitation of the size of the channel is also recommended to avoid overcrowding of the channel during peak migratory periods, which would place undue stress on the individual fish trying to negotiate passage. This would effectively bottle-neck the migration and be detrimental to the breeding potential of the species. It is recommended that a vertical slot fishway have pools that measure at least 1 m in length to be regarded as being ecologically sound.

5.3.3.5. Submerged flow conditions

The hydraulic characteristics of a vertical slot fishway channel are thought to function optimally only under submerged flow conditions. This implies that the most optimal hydraulic conditions for passing of fish are only met once submerged flow conditions are provided through adequate discharge rates. The results from the laboratory experimentation, however, showed that a large proportion of the test population was successfully negotiating the fishway channel under discharge values as little as 24.9% of the volume required to maintain submerged conditions (a fishway channel was considered ecologically successful when test conditions allowed for 80% passing of the test population during this study). This means that a vertical slot fishway based on the design proportions used for the laboratory trials could be considered ecologically functional over a much larger range of flow conditions than previously thought. This is relevant when designing fishways for rivers that experience a high variance in flow volumes, such as the vast majority of rivers throughout South Africa and could be utilised as a means to reduce the overall costs of a fishway, or when calculating how

235 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS much water is required to maintain a fishway. This is relevant to developments such as flow gauging or hydropower schemes.

5.3.3.6. Minimum flow depth

Further results indicated that a minimum flow depth is required to allow fish free passage through a vertical slot channel. Although some individuals of various species were able to negotiate the channel partially under conditions where super critical flow hydraulic conditions predominated, the low percentage of the test population to successfully negotiate the channel means that the channel under these hydraulic conditions cannot be considered functional.

5.3.3.7. Channel substrate

It was postulated that placing a pebble substrate on the floor for the channel would provide altered hydraulic conditions that provide greater opportunity for small-bodied species to negotiate the fishway by providing a greater degree of sheltered flows, counter currents and resting places. It was found that the pebbles used (with an average diameter of 80-100 mm) were too large for the channel dimensions and the discharge rates that could be generated by the laboratory pumps as the water merely flowed through the interstitial spaces. This hampered movement of fish through the channel. It is thought that placement of pebbles of this size would be beneficial only to enhancing the mobility of aquatic macro invertebrates through the channel and should be utilised only where a relatively deep fishway channel could be maintained with a relatively high discharge rate. Functionality could be further enhanced through embedding the lower half of the pebbles into the concrete of the lower surface of the channel, which would largely reduce the interstitial spaces whilst still inducing vertical counter currents and hydraulically sheltered areas. The focus of this study was on fishways that cater predominantly for inland fish species. The consideration of pebble substrates and the maintenance of greater water columns within each pool would be aimed at coastal fishways, where migration of aquatic macro invertebrates and juvenile eel species are important to maintain, together with a large diversity of fish species and size classes. This implies that a large range of swimming abilities has to be catered for. Fishways aimed at catering for inland species do not have to accommodate the specialised designs that are required for passing juvenile eels and aquatic macro invertebrates and therefore inland fishways tend to be simpler in design and more economical in construction.

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5.3.3.8. Placement of the fishway entrance

One of the most pertinent design features that cannot be over emphasised is the importance of the fishway entrance and the associated attraction flows. No matter how hydraulically functional a fishway is, it cannot be regarded as ecologically functional if fish cannot find the entrance to the fishway to attempt upstream passage. The orientation and design of the barrier should be studied to determine where fish would most likely congregate. This is normally in the vicinity of the base of the weir where plunging flow occurs. It is also normally where the greatest portion of flow is directed, or along the periphery of these areas. The fishway entrance should ideally be placed near to this area. If the design specification or site characteristics do not allow for this, the supplementary flow should be supplied to the area near the entrance of the fishway to add to the attraction flows.

5.3.3.9. Dealing with floating debris, siltation and management of the fishway

Other important points to consider during the design process of a fishway is debris accumulation, functionality over periods regarded as optimal migratory periods, regulation of the river, flooding events to scour sediments (recommended), robustness to withstand floodwaters and transported debris. Access for monitoring and maintenance is also considered important, together with security to stop vandalism and exploitation of the large volumes and density of fish that normally accumulate at a fishway. This all requires that a person or organisation take ownership of the fishway to ensure that the abovementioned factors are carried out. Monitoring is considered important as fishway design throughout South Africa can still be regarded as being within early refinement stage and therefore data on functionality is important. Important is accuracy of construction so that pools and repetitious, which would ensure uniform and predictable hydraulics. This allows for future repeatability of the structure, as well as monitoring and studies to be conducted for future developments of fishway design.

Aspects such as silt loads of the river, and a means to scour out silt deposition within the fishway would also have to be considered in fishways where pebble substrates are utilised. This type of modification, which would be considered cumbersome and relatively costly to construct, would be limited to coastal systems (where silt loads of rivers are at their highest), or where specific conservation aims and objectives are to be fulfilled. 237 | P a g e CHAPTER 5: GENERAL CONCLUSIONS & RECOMMENDATIONS

5.3.3.10. Modifications to standard vertical slot fishway

The final design of the fishway incorporated into Blouputs Weir on the Orange River is resulting fishway was designed as a modified version of a vertical slot-type fishway, with a gradient of 1:10 and a 200 mm change in water levels between successive pools. Modifications included the fitment of sills within each slot opening, which assured a minimum volume within each pool, with a minimum depth of 600 mm, which allowed for greater functionality of the fishway under flow conditions that were too low to satisfy submerged flow conditions. A further modification included the removal of all internal baffles orientated parallel to the slope of the channel typical of a standard vertical slot and the centralisation of the slots within the dividing walls between successive pools within the channel. The upper edge of the sills was also sloped toward the downstream side in order to limit the degree of breakaway (that would otherwise induce an air cavity) on the downstream edge. This fishway was monitored for functionality on three occasions, representing three variations in seasonality and three different flow rates. Further monitoring is recommended, but preliminary results indicated that this fishway design caters sufficiently for the species during pertinent periods (peak migratory periods) within the system and therefore the modifications to the standard design allowed for a fishway that retained ecological functionality yet successfully reduced the cost of construction. The modifications of the design of the fishway successfully reduced the overall cost of the construction, as well as the time required for the construction period. This design could therefore be regarded as successful in achieving the goals of producing a better cost-benefit ratio for fishways. It should be noted that this fishway type was aimed at an inland, relatively regulated river, with a fish species community that are all regarded as relatively strong swimmers. The aim of designing this fishway was not to provide a generic design for all rivers throughout South Africa, and so this design does not claim to offer that.

The addition of horizontal grooves along the side walls throughout the fishway pools and slot opening at various heights from the channel floor was an addition to the design of the vertical slot fishway at Blouputs (Chapter 4: Case studies) was an attempt to improve passability of invertebrates. Horizontal grooves were placed within the side walls of the pools just downstream of the slot openings. The functionality of this modification, although seemingly sound in theory, could not be verified during the field surveys.

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5.4. REFERENCES

Bok, A., Kotze, P., Heath, R. and Rossouw, J. (2007). Guidelines for the planning, design and operation of fishways in South Africa. WRC Report No. TT 287/07. Water Research Commission, Pretoria, South Africa. Bunt, C.M. (2001). Fishways entrance modification enhance attraction. Fisheries Management and Ecology, 8: 95-105. Davies, B. and Day, J. (1998). Vanishing waters. University of Cape Town Press, Cape Town, South Africa. p 487. Laine, A. (1990). The effects of a fishway model hydraulics on the ascent of vendace, whitefish and brown trout in Inari, northern Finland. Aqua Fennica, 20: 191-198. Peake, S. (2004). An evaluation of the use of critical swimming speed for determination of culvert water velocity criteria for smallmouth bass. Transactions of the American Fisheries Society, 133: 1472–1479. Pon, L.B. 2008. The role of fish physiology, behaviour, and water discharge on the attraction and passage of adult sockeye salmon (Onchorhynchus nerka) at the Seton River Dam Fishway, British Columbia. Unpublished M.Sc. Thesis, University of British Columbia, Canada. Schmidt-Nielsen, K. (1998). Animal physiology: adaption and environment, 5th edn. Cambridge University Press, Cambridge, United Kingdom. Schwalme, K., Mackay, W.C., and Lindner, D. (1985). Suitability of vertical slot and Denil fishways for passing North-temperate non-salmonid fish. Canadian Journal of Fisheries and Aquatic Science, 42: 1815-1822. Skelton, P. (2001). A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa. Stuart, I. G. and Mallen-Cooper, M. (1999). An assessment of the effectiveness of a vertical-slot fishway for non-salmonid fish at a tidal barrier on a large tropical/subtropical river. Regulated Rivers: Research and Management, 15 (6): 575-590. Rossouw, J., Kotze, P., Bok, A., Heath, R.A. and Ross, M. (2007). Twin-channel vertical-slot fishway designs and tests. WRC Report No. KV 197/07. Water Research Commission, Pretoria, South Africa. White, L.J., Harris, J.H. and Keller, R.J. (2011). Movement of three non-salmonid fish species through a low-gradient vertical- slot fishway. River Research and Application, 27: 499–510.

239 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SOUTH AFRICA, KNOWLEDGE BASE AND ASSESSMENT OF

FUNCTIONALITY (UPDATED FROM BOK et al., 2007).

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Monitored since June 2004 by Pool and Weir design University of Venda WMA: 2 Xikundu Weir; Limpopo System, incorporating a standard Twenty of a possible 28 species Fouché & S 22º 43’ 36” 2003, DWS (gauging & Not functioning optimally Luvuvhu River horizontal weir with were able to locate and enter the Heath, 2013 E 30º 47’ 44” diversion weir) staggered notches fishway; entrance to the fishway is well placed and accessible Limpopo/ WMA: 2 APH007 Single pool and huge Luvuvhu River given in Bok S 23º 03’ 18” DWS (gauging & drop, not designed as a ND, Non-functional ND Latinyande et al., 2007 E 30º 14’ 42“ diversion weir) fishway tributary Limpopo/ Private WMA: 2 given in Bok Luvuvhu River (Marimane Weir Pool and weir Reported to be functional Dr. P. Fouche; Mr. M. Angliss Locality unknown et al., 2007 Nzhelele river reserve) Pool & slot with Limpopo/ WMA: 2 Rabali staggered notches Non-functional but new and University of Venda in September given in Bok Luvuvhu River S 22º 52,824” DWS (gauging & (vertical slot type) with operational (Afrikon) 2004 et al., 2007 Nzhelele River E 30º 06,619” diversion weir) downstream slope Limpopo/ WMA: 2 Private Weir given in Bok Luvuvhu River S 22º20’55” (Popallin Pool and weir Functional None (irrigation) et al., 2007 Nwanedi River E 30º35’41“ Ranch) Waterpoort WMA: 5 Limpopo system; 2001, (A7H001); given in Bok S 22º 45’ 30” Vertical slots Not working no water ND Sand River DWAS gauging weir, et al., 2007 E 29º 36’ 51” crump WMA: 2 DWS (after given in Bok Olifants S 24º 03’ 32” Mamba Pre-barrage Monitoring difficult none 2000) et al., 2007 E 31º 14’ 14“ WMA: 2 Twin slot fish ladder and pers. comm. Olifants River, 2008/2009, Balule S 24º 03’ 23.5” Pre-barrage (pool & ND ND Wessels, KNP DWS (B7H026) E 31º 43’ 15“ weir) 2014

240 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Requires removal of sediment: not effective, Concrete Pool & weir baffle design needs to be with staggered notches Silwervis Dam changed (large height diff Limited data, but observations have Olifants system; with no downstream WMA: 2 (B9H002); 7 m >30cm between pools and confirmed design problems Olifants River slope given in Bok S 23º 12’57.7” 1982, KNP high spillway shape of notch between 1995 no fish found in pool and weir tributary, High flow becomes et al., 2007 E 31º 13’11.3“ wall pools) Natural fishway: 93 (13 species) Shingwedzi River natural fishway better  Requires regular clearing of from natural fishway. used by upstream debris to function migrating fish  Large height between pools  Natural fishway preferred Functional/successful, Pool & weir with effective, looks well staggered notches 37m maintained, some minor Excellent data, 18 species plus Olifants system; Kanniedood long; steep fishway changes needed most large numbers of small fish (<50 WMA: 2 Olifants River Dam; cement gradient of 12.7 to 14.2; effective low and medium mm) used fishway given in Bok S 23º 08’12.7” 1992, KNP tributary, wall; 7 m high large pools sluice gate flow 1992-1995: 3178 comprising 18 et al., 2007 E 31º 27’16.3“ Shingwedzi River (B9H003) at fishway exit (upper  Requires regular clearing of species (incl 2 eel) wide size range pool notch) can control debris during high flows 18 of the possible 22 flow  Difficulty finding entrance during floods Original -Natural, using bedrock on river bank Pioneer (consisting of notch in (Mopani) Dam Limited monitoring data; internal spillway wall and series Olifants system; 1976; (9m), concrete report available WMA: 2 of natural pools and Functional, effective, some Groot Letaba upgraded buttress; 12.5 Natural/old fishway: 252 (13 given in Bok S 23º 31’32.6” overflows in gently modifications needed River tributary; after 1995, m species) large and small species et al., 2007 E 31º 23’57.3“ sloping bedrock) plus1) Debris blocking slots Tsende River KNP B8H019 13 of the possible 21 formal pool & weir Tsende River No monitoring on new fishway adjacent to natural with at KNP staggered notches constructed 1995 WMA: 2 Mingerhout Olifants system; Pool & weir with Appears functional, given in Bok S 23º 45’38.3” KNP weir; concrete; ND Letaba River staggered notches; particularly for large fish et al., 2007 E 31º 29’57.6“ 1 to 2 m high WMA: 2 Black Heron Olifants system; Pool & weir plus natural Being rebuilt after 2000 Barrages and berms required for given in Bok S 23º 42’08.9” 2002, DWS (B8H034); Letaba River rock channel floods small fish but utilised by yellowfish et al., 2007 E 31º 12’59.9“ gauging weir

241 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Pre-barrage pool & weir (with submerged Functional; effective, some Engelhard orifices) Excellent data collected; internal modifications needed, Dam; cement 25m sloping channel report 1990, 1994 (source serious flood damage in WMA: 2 wall; 13 m divided into 3 parallel unknown) pers. comm. Olifants system; 1971 KNP February 2000 S 23º 50’21.5” high; 6m high chambers connected by 1262 fish 21 species Wessels, Letaba River DWS 2008 Location of entrance E 31º 38’26.3“ dam submerged orifices All migratory species (adults and 2014 1) Fishway entrance difficult to (B8H018) giving effective, length sub-adults), 19 of the possible 21 find especially at medium 68m species and high flows Oldest functional fishway in SA Functional; needs some Some data after 1993 (by section Piet Grobler modifications; repair ranger) WMA: 4 Olifants system; 1990’s Dam; 165 m Pool & weir, staggered needed, as serious flood 1995 –fish present in pools in lower given in Bok S 24º 13’51.6” Timbavati River KNP long crest; 8 m notches damage in February 2000 part of fishway et al., 2007 E 31º 38’02.4“ high (B7H020) 1) Accumulation of debris a 99 fish comprising 8 species problem 8 of the possible 20 WMA: 4 Oxford weir Olifants system; 1999 Sluicing flumes (no given in Bok S 24º 11’02” (B7H007) ND ND Olifants River DWS separate fishway) et al., 2007 E 30º 49’26“ gauging weir Pool and slot on left given in Bok bank operates from 300 Olifants system; et al., 2007; S 25º .57’879 ℓ/s. Attraction flow Wilge River at 2005 DWS Xusterstroom ND ND pers. Comm. E 29º 12’747“ required. At high flow all Waterval Wessels water should pass 2014 through fishway Fish populations and species distribution distributed well above and below Kanniedood Dam after Kanniedood Dam S 23º 08’ 39.7” Kanniedood Notched pool and weir KNP Functional development of fishway. Olivier, 2003 Shingwedzi River E 31º 27’ 46.7“ Dam on left bank Implication that fishway is functioning well to pass target species. Kalkheuwel – WMA: 3 Crocodile River Crocodile Combined pre-barrage given in Bok S 25º 48’ 33.7” 2004 DWS ND ND at Pelindaba River at slot and pool et al., 2007 E 27º 55’ 36.1“ Pelindaba Nonyane given in Bok Inkomati Unknown locality KOBWA Near natural Monitoring difficult none fishway et al., 2007 Two fishways coupled to Mac-Mac high and low notches of Inkomati system; WMA: 5 Gauging weir, 2002 weir. Baffle blocks on DWS reports that it is given in Bok Sabie River; S 25° 01’ 51.7” crump design ND DWS downstream face high functional et al., 2007 Sabani tributary E 31º 01' 39.8" (EMMET) tail-waters due to rocks X3H023 and sill 242 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Pre-barrages: sluicing flume (large canal with sloping sides) plus Low flows through by-pass WMA: 5 Kruger gate crump weir (no separate channels, high flows direct Inkomati system; given in Bok S 24º 58’10.3” 2002 DWS (X3H021); fishway). A series of pre- by-pass. Steps possibly too ND Sabie River et al., 2007 E 31º 30’55.1“ gauging weir barrages and bi-channel high. Maintenance visits to fishway to make a new rectify. pool and barrages to raise tail water. Inkomati system; WMA: 5 Sloping baffles with pool Functional, human given in Bok Not DWS Hoxani Dr F. Roux Sabie River Unknown locality and weir predation an issue et al., 2007 RAUEcon monitoring. Some data; 17 migratory species of 23 (total individuals 879) in old fishway; no data on rock-ramp Rock-ramp: old: semi- Old fishway partially fishway most abundant fish: WMA: 5 Lower Sabie natural, cement on functional; new rock-ramp Glossogobius giuris pers. comm. Inkomati system; October S 25º 07’21.1” Road-bridge natural rock, has been fishway appears effective Barbus paludinosus (Deacon, Sabie River 2001 KNP E 31º 55’27.5“ causeway replaced by new large1) Location of entrance could Micralestes acutidens 2007) rock ramp fishway be improved Tilapia rendalli Others: Chiloglanis paratus, Labeo ruddi (at night) 22 of the possible 24 species Lower Sabie weir gauging WMA: 5 September Pool and weir, wide Inkomati system; weir (X3H015) given in Bok S 25º 08’58.3” 2001 notch, forward sloping Newly completed; ND ND Sabie River Sabie River at et al., 2007 E 31º 56’26.4“ DWS baffle on west bank Lower Sabie rest camp Pool & slot, wide, Not yet functional – ND. forward sloping baffle; Operates only at high flow. WMA: 5 Ten Bosch also tail-water pool; Inkomati system; Mid-2001 Pool and slot operates at given in Bok S 25º 21’48.4” gauging weir baffles on downstream ND Crocodile River DWAS 4.5 m3/s. Will be rectified et al., 2007 E 31º 57’23.1“ (X2H016) face. Pre-barrages on for low flow to satisfy low crest and pool and Mozambique requirements slot on left bank WMA: 5 Riverside Pool, weir/vertical slot Inkomati system; Mid-2001 given in Bok S 25º 24’06.6” gauging weir combination on south Newly finished; ND ND Crocodile River DWAS et al., 2007 E 31º 36’22.9“ (X2H046) bank

243 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Natural type/pool & notched weir on south WMA: 5 Leopard Appears functional, prone Inkomati system; 1995 bank, plus 4 pool & given in Bok S 25º 26’ 27.9” Creek; 1-2 m to debris blockage (water No hard data; appears to work Crocodile River Private notched weir type et al., 2007 E 31º 31’ 46.5“ high weir hyacinth) fishways along the length of the weir Pool & weir, forward sloping baffle, rock pool WMA: 5 Komatiepoort with 2 slots. Left bank given in Bok Inkomati system S 25º 26’10” DWS (X2H036); pool and vertical slot. ND Dr F. Roux confirms working et al., 2007 E 31º58’56“ gauging weir Right bank a series of pre-barrages for higher flows WMA: 5 Hoogenoeg 1 partly functional. Other Only B. marequensis (Dr. J. Inkomati system S 26º 02’07” 1995 DWAF (X1H001) Pool and weir AfriDev, 2005 broken Engelbrecht) E 30º 59’51“ gauging weir Lebombo Pool and weir, alternate WMA: 5 gauging weir, Functional. Well-designed, Inkomati system; notches with forward- S 25º 26’47.9” KOBWA horizontal good condition, should be Dr F. Roux AfriDev, 2005 Komati River sloping baffle, very E 31º 57’21.2“ crump height effective. Functional gentle channel slope ca 1.2 m Functional. Well-designed, M’weti weir, Pool and weir, alternate good condition, but WMA: 5 Inkomati system; horizontal weir notches with forward- entrance located far S 25º 27’04.4” KRIB Dr F. Roux AfriDev, 2005 Komati River crest height sloping baffle, gentle downstream away from E 31º 57’06.2“ 4.68 m channel slope base of weir. Small modification required. Pool and weir, very Dysfunctional. Badly Walda weir, WMA: 5 steep slope of about 1:3, designed, much too steep, Inkomati system; horizontal weir S 25º 43’30.5” KRIB not folded back with not effective most of the Not possible to monitor AfriDev, 2005 Komati River crest height cf E 31º 46’50.8“ entrance about 20 m time (possibly for small fish 7.5 m downstream of weir wall at very low flows?) WMA: 6 Pongola System; 1990’s Nduma Game No data – suspect damage given in Bok S 26º 52 ’14.0” ND No data Banzi Pan KZN Wildlife Reserve and non-functional et al., 2007 E 32º 17 ’21.0“ Modified pool and weir Detailed monitoring programme Nhlabane weir with a sloping baffle: started in 2001, good data, 22 at head of variable depth and flow Well maintained, very 1998; species of fish plus macro- WMA: 6 estuary; rate; 1:10 to 1:12 slope; effective in passing of fish Nhlabane Richards crustaceans can use fishway. Mastenbroek, S 28º 38’28.2” concrete wall Fishway with 98 pools and macro-invertebrates; System Bay Successful passage of fish over a 2003 E 32º 16’09.7“ of 6.25 m ht arranged in a folded- tripping of crest gates on Minerals size range of at least 10 to 310 mm with crest staircase type design weir problematic TL caters well for small and juvenile gates giving a total length of specimens 47 m

244 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Fish chutes and baffles. The crest of the crump weir is 9 m wide and consists of a 3 m wide flat central section with 3 Dr P. m wide fishways with Wessels Combined Lake Mzingazi, Richards Bay, concrete beams (weirs) given in Bok (DWS), crump gauging ND Fish and crab species Mzingazi River uMhlathuze and pools on either side et al., 2007 assisted by weir/fishway of the central section. Dr A. Bok The construction of the crump gauging weir/fishway is the first of its kind constructed in South Africa. Mzingazi Basic sloping channel (1 Functions well and appears WMA: 6 saltwater m wide) through wall Moloi (2012); effective (Dec 2001) but Reported to be working well for Mzingazi River S 28º 46’28.1” 2000 RBM barrier; round side weir; Weerts et al. only for short period over movement of all target species E 32º 04’18.1“ cement weir, operational at high tide (2014) tidal cycle ca. 1.8 m only Badly designed, too steep, needs major modification Tugula River Wakkerstroom WMA: 7 1) Discontinuity of top and System; Thaka 1977 Local Fishway Pool & weir with notches Some data from 1995 - Barbus given in Bok S27º20’21.56” bottom sections River Eastern Municipality (Martins Dam); (modified) anoplus (1 of the possible 3) et al., 2007 E30º09’26.79“ 2) Height from river to first Transvaal 6 m height trough too large 3) Steep slope WMA: 7 Tugela System; Mearns Weir ND. Ramp for eels, 2m ND considered as non- given in Bok S 29º14 ’48 ” 1980s DWS ND Mooi River Diversion Weir high weir functional et al., 2007 E 29º 58’ 12“ Causeway on WMA: 12 access road at Variable depth pool & Gentle slope, good design given in Bok Hluleka S 31º 49’27” 2002 head of weir plus separate ND and should be effective et al., 2007 E 29º 18’05“ estuary; ca 1 eel/prawn ramp m ND, considered non- functional. Eel-ramps WMA: 12 Ramps for eels on both Umtata Weir; poorly-designed, operated given in Bok Mtata River S 31º 33.163” 2002 DWS sides of downstream ND gauging weir over limited range of flows, et al., 2007 E 28º 44.762“ face of weir weir totally submerged during high floods Cwebe water WMA: 12 Variable depth pool and supply Gentle slope, good design given in Bok Mbanyana River S 32º 12’14.2” 2002 weir plus separate ND scheme; 0.5 m thus should be effective et al., 2007 E 28º 52’40.7“ eel/prawn ramp high wall

245 | P a g e APPENDIX A: LIST OF KNOWN FISHWAYS THROUGHOUT SA

Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Variable depth pool and DWESA water WMA: 12 weir plus separate ND gentle slope, good supply given in Bok Nqabara River S 32º 15’35.2” 2003 DWS eel/prawn ramp; fishway design thus should be ND scheme: ca. et al., 2007 E 28º 46’31.4“ projects 16 m into effective 1.2 m upstream pool Series of parallel canals Fort Harden; Non-functional; rapid flow on downstream face at Initial observations show small fish WMA: 12 lower Great over weir crest a problem. given in Bok Great Kei 1989; DWS 90º to river flow can only use lower section of Unknown locality Kei; crump Will place new fishway in et al., 2007 connected by escape fishway gauging weir near future routes Pool and weir (variable Functional but requires Haga-Haga WMA: 12 depth baffle); slope 1:5, removal of debris and No detailed monitoring, but small 1995; Great weir; concrete given in Bok Haga-Haga River S 32º 45’ 13.2” 80 mm head between maintenance required, fish appear to use fishway Kei DM wall; 3.4 m et al., 2007 E 28º 14’ 52.3“ pools (300 x 450 x 280 serious erosion of river successfully high mm) bank below weir Abbotsford Some monitoring data: effective for causeway; small fish from >20 mm, pipe under 1.4m high Pool and weir (with causeway may be a potential Baffles drowned-out at situated within submerged orifices at barrier higher flows and thus not the tidal limit entrance leading to Designed for fry and juvenile Nahoon River suitable for climbers, needs WMA: 12 1990; near top of submerged pipe passing catadromous fish Mzimvubu to extension into low tide level given in Bok S 32º 57’ 52.5” Buffalo City Nahoon through weir) (variable 1991-1992: 5374 fish Keiskamma of estuary; dark tunnel at et al., 2007 E 27º 54’ 55.1“ Municipality estuary depth baffle); slope 1:6; Mondactylus falciformis WMA exit; operate over limited Nahoon River 90 mm head between Myxus capensis flow range; pools too small at Abbotsford pools (500 x 500 x 200 Mugil cephalus for large fish R3H008 weir mm) 5m long Glossogobius callidus under the De Anguilla sp. (unsuccessful) Wall bridge 4 of the possible 9 Poor design and badly sited No data – but considered priority – far from main flow over Gauging weir barrier with significant impact on WMA: 12 Cement tower with sharp-crested weir – needs Keiskamma (R1H015); at catadromous species S 33º 11’08.0” 2003 DWS submerged orifice on re-design, non-functional in Lewis (2006) River tidal limit of Myxus capensis and Mugil E 27º 23’28.1“ downstream side present state. Will replace estuary cephalus in tail-water tool below with sloping baffle fishway weir in near future WMA: Irregular series of pools Not considered fully Only C. carpio, T. sparrmanii and L. Goosebay pers. obs. Vaal River S 26º44’18” DWS with surface slots closed functional due to large capensis sampled in fishway by weir (C2H140) Ross E 27º35’30“ at the top. drops between pools RAUECON Functional but flooded (pending upgrade) pers. comm. WMA 2008, DWS; Klipplaatdrift sampled 6 of the possible 9 species Middle Vaal Pre-barrage pool and Fishway since upgraded Wessels, S 27º 23’ 22” Upgraded Gauging Weir sampled (old fishway); System weir, concrete (2012) to a series of pre- 2014; Ross & E 26º 27’ 50“ 2012 (C2H061) No data for new fishway. barrages located in the Ross (2009) centre of the watercourse.

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Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Pool & Weir; Functional, but built to be Marksdrift slope 1:10 effective at medium and WMA: 14 Weir Concrete lower flows only (smaller Orange River S 29º 09’43.3” (D3H008) Situated near the centre species of fish). High flow Observations, no hard data System main E 23º 41’45.4“ Benade et 1989 DWS gauging and of the river bed on a completely inundated and 0 of the liable 8 channel Orange River at al., 1995 water transfer; natural rock outcrop largely non-functional. (upper Orange) Marksdrift 4.2m height leading to the lowest1) Fish can negotiate weir

low notch notch of this gauging itself at med and high flow weir 2) Cannot find entrance Non-functional. Much too steep, completely non- functional as fishway, impassable Douglas Weir Hastily and badly designed. Pool & weir; slope 1:2 Observations – serious design Orange River (C9R003); Extremely high turbulence WMA: 14 (very steep), high (over faults, no fish movement possible of System main 1989 gauging and and velocities unsuitable for Benade et S 29º 02’36” 6m) barrier fish falling back & washed out of channel (Lower DWS diversion; 6.29 fish migration al., 1995 E 23º 50’13“ Reinforced concrete fishway after first few pools Vaal) m height of all  Slope of 1:2 much too 0 of the liable 8 notches steep  Pools to small  Step height too high  Wrong position of fishway (right bank) Limited data from 1994/1995; more monitoring required Vertical slot; slope 1:10, L. aeneus left of centre of river L. capensis Neusberg weir channel Benade et Functional, appears C. gariepinus (D7H014); First time vertical slot al., 1995 effective in passing both B. trimaculatus Orange River WMA: 14 Lower gauging and concept used in SA. 1994 DWS large and small fish; but Size<:50mm->500mm length System main Orange WMA diversion weir; Large and well- Reinforced locating entrance a problem breeding and feeding migrations channel (Middle S 28º 46’28.8” 7.4 m constructed Small concrete Fish may have difficulty 4 of the possible 8 are liable Orange) E 20º 43’20.7“ Orange River fishway included in the finding entrance especially L. capensis dominate numbers, but at Kakamas flow director wall at the during high flows L. aeneus, B. trimaculatus, T. South left low flow notch to sparrmanii, C. gariepinus, B. pers. obs. provide access for fish paludinosus and P. philander Ross moving upstream sampled in fishway over 5 surveys.

WMA: 14 Lower Zeekoebaardt pers. comm. Orange WMA (D7H008) Pre-barrage pool and Orange 2008, DWS ND ND Wessels, S 29º 01’49” Boegoeberg weir 2014 E 22º 11’10“ Dam

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Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height WMA: 14 Lower pers. comm. Orange WMA Pre-barrage pool and Orange 2008, DWS Sendelingsdrift ND ND Wessels, S28° 04’ 33.0” weir 2014 E16° 53’ 54.2” L. capensis, L. aeneus, B. WMA: 14 Lower pers. comm. Appears to function trimaculatus, B. hospes, A. sclateri, Orange WMA Blouputs Wessels, Orange 2012, DWS Pool & slot (preliminary findings of 3 C. carpio, C. gariepinus, P. S28° 30’ 48.2” D8H014 2014; and surveys philander, T. sparrmanii, M. E20° 11’ 11.6” this study brevianalis 1995; lower section passes larger fish Hermanskraal Pool and weir Pool & weir:1993 high flow: 508 diversion weir; (downstream section) (3sp) Great Fish River WMA: 15 (Q9H001) plus pipe unusual 3 C. gariepinus (spawning) Fish to S 33º 08’25.4” Low traction flows could be Deacon et 1991, DWS Great Fish sections, pool & weir, Barbus aeneus Tsitsikamma E 26º 36’19.7“S improved al., (1995) River@Fort large resting pool, Cyprinus carpio WMA “ Brown fishway tunnel passing Anguilla sp Peninsula; 6 m through weir wall 1994 low river flow no data 8 viable species to use, actually used by 4 Good data recorded in unpublished Pool and Weir set report in 1995: 887 in fishway and diagonally across face of Good condition; used 1011 in trap at exit (4sp) weir. Modified, crudely successfully by small fish at Myxus capensis Kowie Ebb built variable depth low flows, needs design Mugil cephalus(>20 to <260mm) and flow weir baffle pool and weir; modifications Mondactylus falciformis and road slope ca. 1:6, 18m Finding entrance Glossogobius callidus Bok & causeway; length  Wrong location of entrance Anguilla sp elvers- unsuccessful WMA: 15 1993 Port Cambray, concrete, ca. 60cm wide, 50cm deep  Variable size of pools Velocities 0.9-1.8m/s Kowie River S 33º 32’39.0” Alfred 1995, 2003; 3m high and 50cm long Built for Lewis (2006): Myxus capensis and E 26º 46’52.3“ Municipality  Fish washed out of fishway Bok et al., constructed at small <100mm Mugil cephalus  Pools too small for large 2004 the tidal limit catadromous fish to fish/ (***experimental testing done by of Kowie migrate as larvae and Successfully facilitates the Lewis, 2006 with vertical slot and estuary juvenile from estuary to migration of estuarine fish sloping baffle) freshwater reaches of under optimal flow 4 of the 9 liable Kowie River conditions Complete to all fish except eels during low and medium flows, partial barrier during high floods. 2002 Natural rock ramp/pool WMA: 15 Bulmers Drift Eastern & weir type for small Appears a bit steep, does not given in Bok Swartkops River S 33º 45’09.0” causeway, ca. No sampling to date Cape catadromous fish and operate at extremely low flows et al., 2007 E 25º 20’31.3“ 1.5 m DRPW climbers

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Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Geelhoutboskl Gamtoos system; Pool and weir (variable WMA: 15 oof weir; Weir damaged in 1994; Initially functional, seen to pass given in Bok Geelhoutbos 1990 DEAT depth baffle) for small Unknown locality concrete weir; leaking badly, needs repair small fish, little data et al., 2007 River (100 mm) fish 1 m high Non-functional. Wrong WMA: 15 Gauging weir Kouga River@ Pool & weir (no pool design; Bass at site in main given in Bok S 33º 47’31” 1990 DWS (L8H005), No data; observations at low flow Stuurmanskraal depth) channel, therefore fishway et al., 2007 E 24º 01’58“ crump design not required Channel with flat v- Rooiwal Non-functional. Tower may WMA: 15 shaped baffles and Groot River gauging weir function at high tail-water given in Bok S 34º 01’55.8” 1998 DWAF tower fishway with No data (East) (K8H006) pool levels. DWAF will et al., 2007 E 24º 11’43.0“ entrance on downstream crump design change design side Bridge on Good condition; design gravel road to Pool and notched weirs problems as water falls in Gourits system; WMA: 16 1998 local given in Bok Gamkaberg with vertical edges & low arc, not effective at high ND to date Olifants River Unknown locality Municipality et al., 2007 reserve; ca. 2 side-walls flows. Should be effective m high at low flows WMA: 17 Farmers weir; Olifants River 1999 Pool and weir for small Functions well at low flows Some recent data (Mr D. Impson, given in Bok S 32º 33’59.5” near Citrusdal; Boskloof tributary Private fish (<200 mm) for small fish Western Cape Conservation) et al., 2007 E 19º 03’04.1“ 3.0 m Goedverwaght Berg River WMA: 19 , Piketberg; Early 2003, design Pool and weir (variable given in Bok System Platkloof S 32º 51’10” 2003 DAD Platkloof weir; problems at exit and ND passage depth) et al., 2007 River E 18º 42’05“ Dept. entrance Agriculture WMA: 19 1948 Non-functional, state of Stellenbosch Harrison, Eeste River S33º56’35.8” Provincial Pool and weir disrepair No data available weir 2m 1951 E18º50’40.7“ Admin Probably first fishway in SA Non-functional, state of disrepair (30-40 years); Tulbagh Poort channel sediments No hard data available, some Fishway Pool and weir with completely blocking descriptive reports after Berg River WMA: 19 Little Berg notches constructed on entrance to fishway; construction. Fishway designed for Harrison, System, Little S 33º 11’04” 1951 DWS River at a 4.5m diversion weir fishway entrance 30m exotic trout 1951 Berg E 19º 09’23“ Mountain View (with orifices) downstream of weir 0 of the possible 6 Diversion weir  Position of trance – no fish TMS: Barbus andrewi (G1H021); 5 m in or out  Sedimentation at entrance

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Barrier name, River system DWA WMA & Date built & Monitoring data (fish species description & Design of fishway Condition & problems References (tributary) Coordinates owner passed) height Functional, barrier in river bed to Rondevlei spillway affects upstream migration. while suitable for large WMA: 19 1998: City Pool and weir with strong swimmers such as Seekoeivlei- On Rondevlei given in Bok S34º04’15.07” of Cape notches, 13 cm drop trout and salmon, is wholly ND Rondevlei spillway et al., 2007 E18º30’15.80“ Town between pools unsuitable for the Rondevlei flow regime and the type of fish that would be in a position to attempt use of it. Harrison Under S33º 58’ 51.02” City of Cape Cape Town City ND 1951; Luger Liesbeek River Paradise Road ND E18º 27’ 11.71“ Town Engineer’s Department & Davies Bridge 1993 (KNP = Kruger National Park). WMA = Water Management Area; NC = not yet constructed; UC = under construction; ND = no data.

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References

AfriDev Consultants. (2005). Hydrology and System Operation. Komati Catchment Ecological Water Requirements Study. Report No. RDM X100-01-CON- COMPR2-0504. Department of Water Affairs and Forestry, Pretoria, South Africa.

Benade, C., Seaman, M.T. and De Vries, C.P. (1995). Fishways in the Orange River system: Neusberg Weir fishway, Marksdrift Weir fishway & Douglas Weir fishway. In: Bok, A. (ed.). Proceedings of the fishway criteria workshop, D’Nyala Nature Reserve, Northern Province 2-5 May 1995. Water Research Commission and the Department of Water Affairs and Forestry, Pretoria, South Africa. Bok, A.H. and Cambray, J.A. (1995). Kowie River ebb and flow fishway: monitoring of fish movement during January and February 1995. In: Bok, A. (ed.). Proceedings of the fishway criteria workshop, D’Nyala Nature Reserve, Northern Province 2-5 May 1995. Water Research Commission and the Department of Water Affairs and Forestry, Pretoria, South Africa.

Bok, A.H. and Cambray, J.A. (2003). Fish movement through a small weir-pool fishway at the tidal limit of a seasonal river in the Eastern Cape, South Africa. Pan- African Fish and Fisheries Association (PAFFA), Third International Conference, Book of Abstracts. p. 114.

Bok, A., Rossouw, J. and Rooseboom, A. (2004). Guidelines for the Planning, Design and Operation of Fishways in South Africa. WRC Report No. 1270/2/04. Water Research Commission, Pretoria, South Africa.

Deacon, N., Paterson, A., Ter Morshuizen, L. and Buxton, C.D. (1995). The movement of fish through the Hermanskraal Weir fish ladder under both high and low flow conditions. Proceedings of the fishway criteria workshop, D’Nyala Nature Reserve, Northern Province 2-5 May 1995. Water Research Commission and the Department of Water Affairs and Forestry, Pretoria, South Africa.

Fouché, P.S.O. and Heath, R.G. (2013). Functionality evaluations of the Xikundu Fishway, Luvuvhu River, South Africa. African Journal of Aquatic Science, 38 (suppl.): 69-84.

Harrison, A.C. (1951). The Tulbagh Poort fish ladder. Piscator, 18: 44-47.

Lewis, H.V. (2006). Evaluation of fishway designs for use at the Ebb and Flow region of rivers in the Eastern Cape, South Africa. Unpublished M.Sc. Thesis. Rhodes University. Grahamstown, South Africa.

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Luger, M. and Davies, B. (1993). Environmentally insensitive design and construction, the Liesbeek River walkway, Cape Town. Environmental Planning and Management, 5(1): 4-11.

Maloi, P.C. (2012). The Mzingazi gauging weir and its effects of the fish and macrocrustacean communities of Lake Mzingazi. Unpublished M.Sc. Thesis. Department of Zoology, University of Zululand, South Africa. Mastenbroek, W.K. (2003). Monitoring studies on the Richards Bay minerals variable passage-depth pool and weir fishway located in the Nlabane Estuary, KwaZulu- Natal. Unpublished Ph.D. Thesis. University of Durban, Durban, South Africa.

Olivier, L. (2003). The effectiveness and efficiency of the Kanniedood Dam fishway in the Shingwedzi River, Kruger National Park, South Africa. Unpublished M.Sc. Technologiae Thesis, Department of Nature Conservation, Technikon Pretoria, South Africa. p. 68.

Ross, M.J. and Ross, T.M. (2009). Proposed construction of a new DWAF gauging weir C2H061: Vaal River at Klipplaatdrift. Report No. ENV_Klipplaatdrift_03/09. Unpublished EnviRoss CC Report compiled for Enviroworks, Bloemfontein, South Africa.

Weerts, S.P., MacKay, C.F. and Cyrus, D.P. (2014). The potential for a fish ladder to mitigate against the loss of marine-estuarine-freshwater connectivity in a subtropical coastal lake. Water SA, 40(1): 27-38.

252 | P a g e APPENDIX B: LIST OF ABBREVIATIONS OF FISH SPECIES

APPENDIX B: – ABBREVIATIONS OF RELEVANT FISH SPECIES MENTIONED

IN THIS STUDY

The abbreviations of the fish species are based on those provided by Kleynhans (2009) and are the accepted abbreviations used by the Department of Water Affairs and Sanitation (DWS).

Species Scientific Name Common name abbreviation

Anguilla mossambica (Peters, 1852) AMOS Longfin eel Anguilla marmorata (Quoy & Gaimard, 1824) AMAR Giant mottled eel Anguilla benghalensis labiata (Peters, 1852) ALAB African mottled eel Anguilla bicolor bicolor (McClelland, 1844) ABIC Shortfin eel Austroglanis sclateri (Boulenger, 1901) ASCL Rock catfish Barbus anoplus (Weber, 1897) BANO Chubbyhead barb Barbus hospes (Bernard, 1938) BHOS Namaqua barb Barbus paludinosus (Peters, 1852) BPAU Straightfin barb Barbus radiatus (Peters, 1853) BRAD Beira barb Barbus trimaculatus (Peters, 1952) BTRI Threespot barb Barbus viviparus (Weber, 1897) BVIV Bowstripe barb Brycinus imberi (Peters, 1852) BIMB Imberi Chiloglanis anoterus (Crass, 1960) CANO Pennant-tailed suckermouth Chiloglanis paratus (Crass, 1960) CPAR Sawfin suckermouth Chiloglanis swierstrai (van der Horst, 1931) CSWI Lowveld suckermouth Clarias gariepinus(Burchell, 1822) CGAR Sharptooth catfish *Ctenopharyngodon idella (Valenciennes, 1844) CIDE Grass carp *Cyprinus carpio (Linnaeus, 1758) CCAR Common carp *Gambusia affinis )Baird & Girard, 1853) GAFF Mosquitofish Hydrocynus vittatus (Castelnau, 1861) HVIT Tigerfish Labeo capensis (A. Smith, 1841) LCAP Orange River mudfish Labeo congoro (Peters, 1852) LCON Purple labeo Labeo cylindricus (Peters, 1852) LCYL Redeye labeo Labeo molybdinus (du Plessis, 1963) LMOL Laeden labeo Labeo rosae (Steindachner, 1894) LROS Rednose labeo Labeo ruddi (Boulenger, 1907) LRUD Silver labeo Labeo umbratus (A. Smith, 1841) LUMB Moggel Vaal-Orange smallmouth Labeobarbus aeneus (Burchell, 1822) BAEN yellowfish Labeobarbus kimberleyensis (Gilchrist & Vaal-Orange largemouth BKIM Thompson, 1913) yellowfish Labeobarbus marequensis (A. Smith, 1841) BMAR Lowveld largescale yellowfish Labeobarbus polylepis (Boulenger, 1907) BOL Bushveld smallscale yellowfish Marcusenius macrolepidotus (Peters, 1852) MMAC Bulldog Mesobola brevianalis (Boulenger, 1908) MBRE River sardine Micralestes acutidens (Peters, 1852) MACU Silver robber *Micropterus salmoides (Lacepède, 1802) MSAL Largemouth bass *Micropterus dolomieu (Lacepède, 1802) MDOL Smallmouth bass Opsaridium peringueyi (Gilchrist & Thompson, OPER Southern barred minnow 1913) Oreochromis mossambicus (Peters, 1852) OMOS Mozambique tilapia Pseudocrenilabrus philander (Weber, 1897) PPHI Southern mouthbrooder Tilapia rendalli (Boulenger, 1896) TREN Redbreast tilapia Tilapia sparrmanii (A. Smith, 1840) TSPA Banded tilapia *Alien species

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