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Biology and Ecology of the Orange-Vaal Largemouth and Smallmouth Yellowfishes in the Vaal River

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Biology and Ecology of the Orange-Vaal Largemouth and Smallmouth Yellowfishes in the Vaal River Biology and Ecology of the Orange-Vaal Largemouth and Smallmouth Yellowfishes in the Vaal River Gordon O’Brien & Pierre de Villiers (editors) TT 508/11 Biology and ecology of the Orange-Vaal largemouth and smallmouth Yellowfishes in the Vaal River Report to the Water Research Commission Edited by Gordon O’Brien1 and Pierre De Villiers2&3 1Centre for Aquatic Research, Department of Zoology, University of Johannesburg 2Scientific Services, Cape Nature 3Orange-Vaal River Yellowfish Conservation and Management Association WRC Report No. TT 508/11 October 2011 Obtainable from: Water Research Commission Private Bag X03 Gezina, Pretoria 0031 SOUTH AFRICA Email: [email protected] The publication of this report emanates from the WRC consultancies titled: 1. An assessment of selected biology aspects of the two yellowfish species Labeobarbus kimberleyensis and L. aeneus from the Orange-Vaal River system, South Africa (WRC Project No. K8/678). 2. Effects of flow and temperature on spawning and recruitment of Largemouth (Labeobarbus kimberleyensis) and Smallmouth (L. aeneus) yellowfish (WRC Project No. K8/803). 3. Assessment of selected biological features associated with the breeding biology of the threatened Orange-Vaal River Largemouth yellowfish and the Orange-Vaal River Smallmouth yellowfish from the Orange-Vaal River system. (WRC Project No. K8/818). DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the view and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. ISBN 978-1-4312-0165-5 Printed in the Republic of South Africa ii TABLE OF CONTENTS 1. Executive summary ............................................................................................. 1 2. General introduction ............................................................................................ 5 3. Species identification, taxonomy and notes on evolutionary and phylogenetic development. ..................................................................................................... 10 3.1. Taxonomic history of the Vaal River yellowfishes ..................................... 10 3.1.1. Orange-Vaal smallmouth yellowfish .................................................. 10 3.1.2. Orange-Vaal largemouth yellowfish ................................................... 11 3.2. Species identification ................................................................................. 11 3.3. Notes on evolutionary and phylogenetic development .............................. 20 4. Reproductive biology and early development ................................................... 22 4.1. Introduction ................................................................................................ 22 4.2. Review of the known reproductive biology of the Vaal River yellowfishes 23 4.3. Artificial reproduction experiment .............................................................. 26 4.3.1. Introduction ........................................................................................ 26 4.3.2. Materials and methods ...................................................................... 26 4.3.3. Results: .............................................................................................. 40 4.4. Early development of yellowfishes ............................................................ 42 4.4.1. Introduction ........................................................................................ 42 4.4.2. Materials and methods ...................................................................... 44 4.4.3. Results and discussion ...................................................................... 45 Early development of the Smallmouth yellowfish ........................................... 45 Early development of the Largemouth yellowfish ........................................... 51 4.4.4. Conclusions ....................................................................................... 61 5. Age validation .................................................................................................... 63 5.1. Introduction ................................................................................................ 63 5.2. Materials and methods .............................................................................. 66 5.3. Results and discussion .............................................................................. 67 5.3.1. Larval development and hatching ...................................................... 67 5.3.2. Age validation .................................................................................... 69 5.4. Conclusions ............................................................................................... 72 6. Home ranges, habitat use, migrations and general behaviour .......................... 73 6.1. Introduction ................................................................................................ 73 6.2. Materials and methods .............................................................................. 76 6.2.1. The study area ................................................................................... 79 6.2.2. Biotelemetry monitoring methods ...................................................... 80 iii 6.2.3. Yellowfishes used in the study .......................................................... 86 6.2.4. Environmental conditions monitored ................................................. 88 6.2.5. Data analyses methods ..................................................................... 89 6.3. General behavioural biology and ecology ................................................. 91 6.3.1. Consideration of individual behavioural patterns. .............................. 92 6.3.2. Home ranges ................................................................................... 103 6.3.3. Habitat use ...................................................................................... 105 6.3.4. Coordinated migrations ................................................................... 110 Spawning migrations .................................................................................... 111 Migrations of larvae and juvenile yellowfish ................................................. 112 Seasonal migrations of adult yellowfishes .................................................... 113 6.3.5. Comments on possible territoriality behaviour of Vaal River yellowfishes. ..................................................................................................... 114 7. Aspects of the Conservation and management of Vaal River yellowfishes .... 116 7.1. Review of the socio-economic value assessment of Yellowfish in the Vaal River ........................................................................................................ 116 7.2. Review of the impact of angling on yellowfish of the Vaal River ............. 118 7.3. Simplified Regional Scale Risk Assessment of the threats Largemouth Yellowfish in the Vaal River. .................................................................... 120 7.3.1. Introduction ...................................................................................... 120 7.3.2. Materials and methods .................................................................... 121 Problem formulation ..................................................................................... 121 Study area .................................................................................................... 122 Ecological assessment endpoints ................................................................ 124 Habitat identification ..................................................................................... 124 Source and associated stressor identification .............................................. 125 Conceptual site model .................................................................................. 125 Ranking system ............................................................................................ 126 Risk characterisation .................................................................................... 128 7.3.3. Results and discussion .................................................................... 129 Sum of the relative ranks per stressor .......................................................... 129 Sum of relative ranks per habitat .................................................................. 130 Sum of relative risk per endpoint .................................................................. 131 The relative risks per risk region .................................................................. 131 Scenario assessments ................................................................................. 132 7.3.4. Conclusions ..................................................................................... 136 8. Closing remarks and recommendations .......................................................... 137 iv 8.1. Closing remarks ...................................................................................... 137 8.2. Recommendations .................................................................................. 138 9. Acknowledgements ......................................................................................... 140 10. References .....................................................................................................
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