Migration Patterns of Fishes of the Blackwood River and Relationships to Groundwater Intrusion

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Migration patterns of fishes of the Blackwood River and relationships to groundwater intrusion

Report to the Department of Water, Government of Western Australia

Stephen J. Beatty, Fiona McAleer and David L. Morgan

November 2009

Centre for Fish and Fisheries Research, Murdoch University.

Acknowledgements:

This project was jointly funded by the Department of Water Western Australia and the Australian Government under its $12.9 billion Water for the Future plan. Particular thanks are extended Adrian Goodreid, Natasha Del Borrello and Rob Donohue from the Department for their significant contributions in managing the project. Many thanks also to the Department of Water Bunbury team of Ash Ramsay, Richard Pickett, Andrew Bland and Peter Muirden for providing extensive hydrological data throughout the study. We are grateful for the field assistance that was provided by Andrew Rowland, Travis Fazeldean, Simon Visser, Mark Allen, David John, Trine Hansen, Joshua Johnston and Andrew Nunn. Photographs are by the authors except for Freshwater Cobbler by Mark Allen. The study complied with permits provided by the Murdoch University Animal Ethics Committee and the Department of Fisheries, Government of Western Australia.

SJ Beatty, FJ McAleer and DL Morgan

Centre for Fish and Fisheries Research

Murdoch University

South St Murdoch

Western Australia

Email: [email protected]

Frontispiece: Balston’s Pygmy Perch by Lyndsay Marshall

SUMMARY

The Blackwood River catchment is one of two in the Southwest Coast Drainage Division to house all eight freshwater fishes endemic to the region and is therefore of high conservation importance. However, salinisation of the upper catchment has led to substantial range reductions of freshwater species downstream to the largely forested region; where fresh groundwater intrusion by the Yarragadee and Leederville aquifers is greatest. This study represents the only long‐term and comprehensive monitoring of freshwater fish populations in the south‐west of Western Australia, and consisted of 27 monitoring events between October 2005 and September 2009; which provided information on spatial and temporal movement patterns and identified indicator species of adequate groundwater intrusion.

The overall key implication of this study is that it demonstrates, for the first time, that groundwater plays an important role in maintaining relictual fish fauna in a major river system of this region. This study identifies two species that are appropriate as indicators of river connectivity and in the setting and monitoring of Ecological Water Requirements (EWRs) for this river in light of groundwater extraction, increasing salinisation and reduced rainfall (and thus surface water run‐off and groundwater recharge) as a consequence of climate change.

The study specifically identifies Milyeannup Brook (one of two permanently flowing tributaries due to groundwater intrusion) as being of key conservation importance as it houses the only breeding population of the EPBC listed (Vulnerable) Balston’s Pygmy Perch Nannatherina balstoni, and also housed all the other freshwater fishes of the river which were shown to use the system to varying degrees. Microhabitat utilisation by this species within this system during baseflow conditions demonstrated the importance of pool habitats with the Balston’s Pygmy Perch found to only occupy the downstream <1600m of permanent habitat during March (baseflow). To maintain this baseflow population, it is crucial that this groundwater discharge is maintained in Milyeannup Brook.

In the main channel of the Blackwood River, the study found a strong relationship between the upstream movement of Freshwater Cobbler Tandanus bostocki through riffle zones and discharge during the baseflow period, i.e. March in 2006, 2007, 2008 and 2009. The species was found to undergo large localised movements in the main channel of the Blackwood River that were variable both spatially and temporally. Movements during low flow periods (i.e. highest proportional contribution by groundwater to total flow) were best explained and highly correlated with amount of discharge. It is proposed these movements are probably related to feeding rather than spawning activity as large numbers of small, immature individuals (the study found the females of the species matured at ~172 mm Total Length (TL)) were recorded moving through the riffle zones. Furthermore, by examining the reproductive biology of the species, peak spawning was shown to occur from October to December (i.e. outside the baseflow period).

Subsequent modelling of upstream movements of Freshwater Cobbler over two riffle zones during the driest month (i.e. March) determined that the level of discharge and subsequent riffle depths that would preclude upstream passage by the species were 381.5 l/sec (0.18 m depth) and 101.9 l/sec (0.05 m depth), for the riffles downstream and upstream of the major groundwater discharge zone, respectively. The significance of riffle access to sustaining the population requires further research, however, it is the largest bodied fish of the river and obviously utilises these riffle habitats in large numbers during baseflow. Therefore, if baseflow discharge maintains adequate depth on these riffle zones such that this species is able to access them, then it could be assumed smaller bodied fishes could also access or negotiate them. It

2 is therefore proposed (along with ensuring the sustainability of the Balston’s Pygmy Perch in Milyeannup Brook) that this species should become an indicator of ecological river connectivity during baseflow and be incorporated in monitoring the adequacy of determined EWRs of the river. Furthermore, in terms of an ecological trigger, the rate of future groundwater extraction from the Leederville and Yarragadee Aquifers should not exceed that which will continue to enable this species to access these riffle zones during the baseflow period or lead to a reduction in the baseflow stream length in Milyeannup Brook.

These data represent a comprehensive baseline of fish communities in arguably one of the region’s most important river systems, and highlight the value in long term monitoring of a diverse range of aspects relating to the ecology of these fishes. These findings have considerable implication for setting and monitoring Ecological Water Requirements of this and other rivers in this region; particularly in light of regional groundwater extraction pressures and reduced rainfall due to predicted climate change.

Recommendations and future research

• Localised movement patterns of the Freshwater Cobbler through riffle zones in the Blackwood River should continue to be monitored annually during baseflow (March) in order to further validate the models.

• In order to more fully understand the significance of riffle zones to the viability of this species in the Blackwood River, a tracking program (radio tracking and PIT tagging) at key riffle zones should be undertaken in order to determine fine‐scale habitat usage of this species during baseflow. Furthermore, the feeding ecology and specific spawning behaviour of the species should also be investigated.

• Following from the above recommendations, Freshwater Cobbler access to riffle zones during baseflow periods could be regarded as a key ecological trigger in monitoring the adequacy of groundwater discharge from the Yarragadee Aquifer.

• The level of groundwater extraction from the Leederville and Yarragadee Aquifers should be set to allow continued access by Freshwater Cobbler to these riffle zones during the baseflow period.

• Milyeannup Brook is the key tributary from a freshwater fish conservation perspective and ongoing biannual monitoring of its fish communities should occur. This monitoring should take place during baseflow (March) to ensure adequate groundwater maintained habitat is available to sustain the EPBC Act listed Balston’s Pygmy Perch and during the major downstream migration of its juveniles during November to monitor recruitment rates of this crucial population.

• It is recommended that future groundwater abstractions should only occur at levels that do not reduce the amount of baseflow in Milyeannup Brook from its minima of 1600 m from the Blackwood River in 2007.

• Significant decline of the Balston’s Pygmy Perch in terms of the baseflow population abundance in Milyeannup Brook (found to be restricted to <1600 m from the confluence of the Blackwood River) or its annual recruitment success should be a key trigger in determining adequate levels of groundwater discharge from the Yarragadee Aquifer.

• Both acute and gradual salinity tolerances of all species of the Blackwood River require determination in order for predictions to be made on the long term viability of these species in this

river and other secondarily salinised systems in south‐western Australia in light of predicted changes in salinity levels.

• Further genetic studies should occur on the Balston’s Pygmy Perch and Mud Minnow using greater sample sizes. Furthermore, studies are also are required for other endemic freshwater fishes of south‐western Australia in order to determine the genetic variability between populations as this information has direct management implications in terms of prioritising populations for conservation.

EXTENSION OF RESULTS

Major reports (excluding quarterly progress reports)

Beatty, S., Morgan, D., McAleer F., Koenders A. and Horwitz P. (2006). Fish and freshwater crayfish communities of the Blackwood River: migrations, ecology and the influence of surface and groundwater. Centre for Fish and Fisheries Research, Murdoch University Report to South‐ west Catchments Council and Department of Water, Western Australia. Beatty, S.J., McAleer, F.J. and Morgan, D.L. (2008). Interannual variation in fish migration patterns and habitats of the Blackwood River and its tributaries: annual progress report. Centre for Fish and Fisheries Research, Murdoch University Report to Department of Water.

Oral presentations (conferences, workshops and forums)

Beatty, S.J.*, Morgan, D.L., McAleer, F.J., Koenders, A. and Horwitz, P. (2007). Fish and freshwater crayfish communities of the Blackwood River: migrations, ecology and the influence of surface and groundwater. Oral presentation. Australian Society for Fish Biology, Annual Meeting, Canberra, A.C.T. Australia.

Beatty, S.J.*, Morgan D.L. and McAleer F. (2008). Groundwater dependent fish communities in the Blackwood River: understanding migration patterns and the influence of salinisation and river connectivity. Oral presentation. Australian Society for Limnology. Annual Conference, Mandurah, Australia.

Beatty, S.J.*, Morgan, D.L., McAleer, F.J. Fish and freshwater crayfish communities of the Blackwood River: migrations, ecology and the influence of surface and groundwater. Conservation Council of Western Australia: Scientific forum on the environmental issues surrounding the extraction from the Yarragadee Aquifer. Perth, May 2006.

Beatty, S.J.*, Morgan, D.L., McAleer, F.J. Fish and freshwater crayfish communities of the Blackwood River: migrations, ecology and the influence of surface and groundwater. Royal Society of Western Australia. Scientific forum on the environmental studies on the extraction from the Yarragadee Aquifer. Scitech, West Perth, May 2007.

Beatty, S.J.*, Morgan D.L., McAleer, F.J. Fish and crayfish communities of the Blackwood River: migrations, ecology, and influence of surface and groundwater. Western Australia Naturalists Club Lecture Series. Star Swamp Community Centre September 2007.

Beatty, S.J.*, McAleer F.J. and Morgan D.L. Overview of the relationships of fish migrations to groundwater and surface in the Blackwood River Workshop on the Ecology of fish and crayfish in the Blackwood River: relationships to groundwater and surface flows. Environmental Technology Centre, Murdoch University, Perth, September 2007. 5

Phillips N.*, Chaplin J., Morgan D. and Beatty S. The evolutionary significance of Balston’s Pygmy Perch and Mud Minnow populations in the Blackwood River. Workshop on the Ecology of fish and crayfish in the Blackwood River: relationships to groundwater and surface flows. Environmental Technology Centre, Murdoch University, Perth, September 2007.

McAleer F., Beatty S. and Morgan D. Biology of Freshwater Cobbler in the Blackwood River. Workshop on the Ecology of fish and crayfish in the Blackwood River: relationships to groundwater and surface flows. Environmental Technology Centre, Murdoch University, Perth, September 2007.

Table of Contents

SUMMARY ...... 2

EXTENSION OF RESULTS ...... 5

TABLE OF CONTENTS ...... 7

BACKGROUND ...... 8

AIMS OF THE STUDY ...... 9

MATERIALS AND METHODS ...... 10 Study sites ...... 10 Environmental variables ...... 12 Sampling for fish movements ...... 13 Relationships between fish movement and environmental variables ...... 13

Results and Discussion ...... 17 Water quality and discharge regimes ...... 17 Freshwater Cobbler ...... 30 Western Minnow ...... 41 Mud Minnow ...... 54 Balston’s Pygmy Perch ...... 57 Western Pygmy Perch ...... 62 Nightfish ...... 70 Milyeannup Brook baseflow fish habitat associations ...... 80

References ...... 91

Background

The Southwest Coast Drainage Division has the highest rate of endemism of freshwater fish of any division in Australia (Allen et al. 2002). Until relatively recently, there was little information available on the freshwater fishes in the Blackwood River (the largest by discharge in the region), with most fish related research restricted to detailing the estuarine fauna (see Lenanton 1977, Hodgkin 1978, Valesini et al. 1997). Morgan et al. (1998) provided distributional data (40 sites) on the fishes in the lower reaches of the Blackwood River and a major tributary, the Scott River, and Morgan et al. sampled sites from the upper and lower catchment. This research found that the Blackwood River catchment is one of only two to house all eight species of freshwater teleost that are endemic to south‐western Western Australia (Morgan et al. 1998, 2003). Of the fish species known from the Blackwood River catchment: four are listed on the Australian Society for Fish Biology’s List of Threatened Fishes, while one, Balston’s Pygmy Perch has recently (2006) been listed as Vulnerable under the EPBC Act 1999, and, along with the Mud Minnow is also listed as Schedule 1 by CALM under the Wildlife Conservation Act 1950.

Endemic fishes of south‐western Australia have undergone massive reductions in their overall range over the last 100 years (Morgan et al. 1998), largely as a result of modification of habitats, with salinisation of the major catchments a key threatening process. Morgan and Gill (2000) demonstrated that for the various fish habitats in the lower south‐west region that there were significant differences in the fish fauna associated with salinised systems, compared to fresh habitats. For example, salinisation throughout both most of the upper catchment and the main channel of the Blackwood River has led to a decline in the range of many of the salt‐intolerant fishes and much of the upper catchment and main channel is dominated by salt‐tolerant species (Morgan et al. 2003). This impact has undoubtedly occurred in rivers in this region as secondary salinisation (associated with wide‐scale clearance of vegetation for semi‐intensive agriculture) resulting in only ~44% of flow in the largest 30 rivers in the south‐west of Western Australia being fresh; the remainder being brackish or saline (Mayer et al. 2005). The levels and trends on stream salinity and salt loads are variable by catchment with those rivers with catchments originating in cleared, lower rainfall areas (<1000mm) generally having fresher flow in lower reaches (due to freshwater inputs from forested streams and groundwater) than in their headwaters (Mayer et al. 2005).

Potential reductions in river flow in this region may occur as a consequence of reduced rainfall, groundwater extraction and climate change. For example, average annual rainfall in the south‐west of Western Australia has declined 10% since 1970, however the non‐linearity between rainfall and stream‐ flow has contributed to a >50% reduction in average flows into public water supply dams (State Water Plan 2007). The ranges of predicted average annual rainfall declines are: by 2030 between 3‐22% and 0‐ 22% for the extreme south‐west (i.e. the location of the Blackwood River) and the remainder of the region, respectively (Suppiah et al. 2007, who summarised the best‐performing 15 models performed for the IPCC 2007 4th Assessment Report). By 2070, models predict a range of annual average rainfall decline to be between 7‐70% and 0‐70% for the extreme south‐west and the remainder of the region, respectively (Suppiah et al. 2007). This has major implications for the long‐term viability of freshwater fishes of the region and direct implications for sustainably managing surface and groundwater resources.

Ecological importance of groundwater and the Blackwood River

Groundwater has been estimated to account for between 30 and 70% of the world’s total freshwater, with surface waters such as rivers containing <0.01% (Freeze and Cherry 1979, Petts et al. 1999). Many rivers are classified as groundwater‐dependent ecosystems, and are further characterised by the degree of

8 dependency on groundwater (Boulton and Hancock 2006). Groundwater‐dependent ecosystems are complex, often support a relatively diverse fauna and may provide refugia for relictual species, however they vary in their degree of dependency on groundwater to maintain their composition and function (Hattons and Evans 1998, Power et al. 1999, Murray et al. 2003, Humphreys 2006). Localised areas of groundwater water discharge into streams creates a unique environment known as the hyporheic zone. Characteristics of this region are important in maintaining populations of aquatic species, including fish. For example, the hyporheic zone often provides a thermal refuge for aquatic species by buffering against extreme upper and lower lethal temperatures (Power et al. 1999, Hayashi and Rosenberry 2002). The hyporheic zone influences water quality by maintaining flows independent of surface runoff, supplying dissolved oxygen, maintaining stream productivity, and providing habitat and maintaining migratory routes. There are a number of specific examples that document the importance of groundwater to particular species in particular systems, however, Sear et al. (1999) considered that the nature of the importance of groundwater is difficult to determine at a regional scale, but should be assessed at a local or catchment level.

The Yarragadee Aquifer groundwater currently discharges into the Blackwood River in the reach just downstream of Layman’s Brook to just upstream of Milyeannup Brook (Figure 1). Although the Yarragadee groundwater discharge contributes only ~1% of the 940GLyr‐1 of the annual Blackwood River discharge during the dry months, groundwater from the Yarragadee and Leederville Aquifers contribute to between 30‐100% of the discharge depending on the amount of summer rainfall (Strategen 2006). This groundwater discharge effectively dilutes the salinity of the river during dry months; when the tributaries of the river contract or dry completely.

Future reduction in groundwater discharge into the main channel of the Blackwood River is predicted due to allocated water extractions from the Yarragadee Aquifer (Hyde 2006) and reduced recharge from lower rainfall expected from climate change in this region (Hughes 2003). In fact, Golder and Associates (2008) recently found a strong relationship between baseflow in the section of the Blackwood River that this study focuses on and the previous 12 months rainfall. Importantly, they found that this relationship has already changed due to rainfall reductions and extraction.

Aims of the study:

Although information existed on the distribution of fishes in the Blackwood River, no information existed on their movement patterns or habitat use and how these relate to environmental variables; particularly fresh groundwater intrusion.

The overall aim of the study was to relate patterns of fish migrations to prevailing environmental variables in the Blackwood River. Specific aims were to:

• Gather a comprehensive seasonal baseline dataset of the patterns of fish and crayfish movements in the Blackwood River to allow ongoing monitoring of potential biotic changes that may result from predicted alterations to the current hydrological regimes. • Describe the population demographics and migrations of the fish and freshwater crayfish fauna associated within the tributaries of the Blackwood River within the Yarragadee Aquifer discharge zone (i.e. Milyeannup Brook, Poison Gully and Layman Brook) and compare these to adjacent tributaries that are not fed by this aquifer (i.e. Rosa Brook and McAtee Brook). • Identify relationships between migration patterns, population demographics and the key environmental variables. 9

• Identify key indicator fish species for determination and ongoing monitoring of Ecological Water Requirements within areas of groundwater discharge in the Blackwood River and its tributaries.

Materials and Methods

Study sites

Blackwood River main channel

Site selection for determining the temporal changes in population demographics and migrations of the fish and crayfish fauna in the Blackwood River main channel was based on their differing proximities to the major zone of groundwater discharge and to the discharge measurement sites as designated by the Department of Water. For example, in 2005/2006 the fish fauna found within two sites in the Blackwood River main channel that is subjected to the major discharge of ground water (from the Yarragadee or Leederville Aquifers) was compared to two sites upstream of this discharge. In 2007/2008 this was modified to three sites subjected to discharge of groundwater, from either the Yarragadee or Leederville Aquifers, and one site directly upstream of the discharge.

The two sites within the main channel in 2005/2006 that receive groundwater input were immediately downstream of the mouth of Milyeannup Brook (referred to as Milyeannup Pool) (34.0909oS, 115.5661oE) and just upstream of the mouth Rosa Brook (referred to as Denny Road) (34.1081oS, 115.4505oE). Additionally, Gingilup (34.10445oS, 115.51947oE), which is gauged by the Department of Water, was included. The two upstream sites were Jalbarragup Road crossing (34.0421oS, 115.6025oE) and Quigup (33.9736oS, 115.7008oE) in 2005/2006. In 2007/2008 monitoring ceased at Quigup in favour of a compilation of three sites in close proximity; namely Darradup during March 2007, Jalbarragup Road Crossing (as above) from March to November 2007 and Orchid Place in March and April 2008 (see Figure 1).

Sampling was conducted in October, November and December 2005; February, March, June, August and September 2006; March, May, June, August, September, October, November and December 2007 and March and April 2008. Sampling is scheduled to continue until mid 2010.

Blackwood River tributaries

A number of tributaries were similarly monitored for comparison of the aquatic fauna with both each other and the main channel. These include Milyeannup Brook, Poison Gully, Layman Brook, Rosa Brook, McAtee Brook and St Johns Brook. Milyeannup Brook and Poison Gully are directly maintained in dry months (summer/early autumn) by groundwater discharge from the Yarragadee Aquifer. Layman Brook receives groundwater discharge from the Yarragadee Aquifer during winter and spring but not summer; when it ceases to flow and usually dries. The temporal changes in the population demographics and migrations of the fish and crayfish fauna within these tributaries were compared with two adjacent tributaries that flow seasonally, i.e. Rosa Brook and McAtee Brook which are within the Leederville Aquifer discharge zone. In addition, St Johns Brook, which is situated within the Leederville Aquifer discharge zone, was seasonally sampled in June and November 2007 and June 2008.

Seine/electrofishing tributary sites

Tributary fyke net sites

Main channel sites

Quigup

McAtee Bk

Rosa Brook Layman Bk Jalbarragup

Denny Rd Milyeannup Pool Gingalup

Milyeannup Brook Poison Gully

Figure 1 Sampling sites in the main channel and tributaries of the Blackwood River.

Environmental variables

Water quality monitoring

The climatic regime of Bridgetown (the nearest centre where long‐term data was available) for the study period were obtained for the Australian Bureau of Meteorology. These patterns in rainfall and temperature were compared to long term data to provide indications of variability or consistency of the climate during the sampling period with that typically observed for this region. The prevailing rainfall has particular implications for influencing surface flow regimes of the study sites.

On each sampling occasion at each site, the temperature, conductivity, pH, and dissolved oxygen were measured in the middle of the water column at three locations and a mean (± 1 SE) determined. In additional, temperature data loggers (TinytagTM) were placed in situ in the sampling sites and logged water temperature every three hours. Temperature loggers were downloaded every three months.

Discharge, baseflow riffle profiles and stage‐height relationships

Monthly discharge rates in the Blackwood River during the study period were obtained from the Department of Water, Government of Western Australia gauging stations at Darradup, Gingilup and Hutt Pool (Figure 1). Monthly discharges at the sampling sites were estimated from: the Darradup gauging station for the Jalbarragup site, Gingalup gauging station for the Gingalup site, and those for the riffle sites at Milyeannup and Denny Road from a combination of the instantaneous cross‐sectional discharge‐depth profiles taken during baseflow months in 2007, 2008 and 2009 (as part of the cross‐section profiles, see below), and by interpolating discharges from the other adjacent gauging stations for the remaining sampling months. Instantaneous discharges on each sampling occasion were taken in the following tributaries: McAtee Brook (just upstream of the Yarragadee Aquifer Discharge Zone (YADZ), Milyeannup Brook and Poison Gully (within the YADZ and directly receive Yarragadee discharge), Layman’s Brook (within the YADZ but does not receive discharge from the aquifer) and Rosa Brook downstream of the YADZ.

Three baseflow cross‐sectional profiles were taken across the riffle zones at Milyeannup and Denny Rd in March and May in 2007, and March and April in 2008; coinciding with sampling of base‐flow fish movements at those riffles. The relationships between Water Stage Levels (WSL) and discharge over these riffles were then plotted and a number of models fitted in order to select that which provided the best overall descriptions of the relationships between the variables (i.e. usually both the highest coefficient of determination and significance value).

Using the relationships between discharge and mean upstream movement of Freshwater Cobbler over four consecutive baseflow periods (i.e. March 2006, 2007, 2008 and 2009) at Denny Road and Milyeannup Pool, the discharge and stage heights at each riffle, and the depths across the profiles at different stage heights, estimates of the minimum discharge and riffle zone depths for upstream Freshwater Cobbler movement were determined (see below Relationship between baseflow hydrology and riffle usage).

Sampling for fish movements

A number of techniques were employed to examine the fish fauna of the main channel and tributary sites in the Blackwood River. Each method is outlined below, i.e. the use of fyke nets (11.2 m in width, including two 5 m wings and a 1.2 m wide mouth fishing to a depth of 0.8 m, 5 m long pocket with two funnels all comprised of 2 mm woven mesh); seine nets (5, 10 and 15 m nets comprised of 2 mm woven mesh and a 26 m seine net consisting of two 9 m wings of 6 mm woven mesh and an 8 m bunt of 3 mm mesh); 240 and 12 v electrofishers; and crayfish traps during 2005/2006. During the 2007/2008/2009 sampling concentrated on emerging trends in migration patterns and utilised fyke nets.

Blackwood River main channel

Species migrations

At the main channel sites (see Figure 1), fyke nets were used to determine temporal trends in species migrations. Fyke nets were set facing upstream, to determine downstream movements of fish, and facing downstream, to determine upstream movements of fish. Each fyke net was set for a period of 72 hours and sampled every 24 hours.

Each fish captured was identified, a sub‐sample measured (total length (TL) for fish and orbital carapace length (OCL) for crayfish) to the nearest 1 mm and where possible sexed and released. A subsample of Freshwater Cobbler were retained for analyses of biological indices such as gonadal development and aging as this species was identified as a key indicator species (see Results).

The mean number of each species captured on each occasion was adjusted to account for total number of each species migrating through a section of the river. The total numbers referred to here on in are the actual numbers captured, while the migration figures reflect the adjusted data to show the approximate numbers of fish actually migrating and to thus allow for comparisons between the various riverine reaches.

Blackwood River tributaries

On each sampling occasion (during stream flow), fyke nets were set over 72h in Milyeannup Brook (two sites). Additionally, Layman Brook, Rosa Brook, McAtee Brook and Poison Gully (Figure 1). At each site, one net was set facing upstream, to capture fish that were moving downstream, while another was set facing downstream (to capture fish moving upstream) and each was checked every 24 hours. As with the main channel site captures, the percent coverage of each set was determined and the catches later adjusted to 100% of the stream width.

The shallow, diffuse nature of Poison Gully required smaller fyke nets. These were used elsewhere, but still consisted of 2mm woven mesh. The same methodology i.e. three, 24h sets was utilised with these modified fykes. Fish species were identified, with a large sub‐sample measured for total length (mm TL) before being released. Those not measured were identified and counted to determine total numbers and immediately released. A small sub‐sample of native species was retained for biological investigation into the gonadal development (up to ~30 per month) and for genetic analysis (see Phillips et al. (2007) for Nannatherina balstoni and Galaxiella munda).

Relationships between fish movement and environmental variables

Regression analysis was undertaken for a number key species in the tributaries, and for the Freshwater Cobbler in the main channel (the species identified as an appropriate indicator of river connectivity due to 13 the apparent relationship to baseflow discharge by Beatty et al. (2006)). Freshwater Cobbler movement pattern analysis was also refined via specific sampling of key riffle zones during baseflow and also undertaking complementary hydrological data including cross‐sectional profiles and discharges at those monitoring sites (courtesy of the Department of Water, Bunbury). This was aimed at estimating the flow requirements to maintain migratory ability through key riffle zones during base‐flows.

Tributaries

Overall analysis

The fishes included in analyses were those where adequate migration data were recorded (i.e. utilised the most number of tributaries). These species included the Western Minnow, Western Pygmy Perch and Nightfish. The relationships between the upstream and downstream movement of the above species during the major flow and breeding periods (i.e. the period that all four tributaries were flowing, August to December) and the prevailing environmental variables in Milyeannup Brook, Rosa Brook, McAtee Brook, and Layman’s Brook were determined (see Beatty et al. (2006) for details of the specific statistical analyses).

Milyeannup Brook baseflow monitoring

Finer scale monitoring of fish and crayfish populations and environmental variables along Milyeannup Brook was undertaken at those sites previously examined during baseflow conditions in 2006 (see Beatty et al. 2006 for the location of the sites in Milyeannup Brook). Sampling took place in March 2007 and 2008 and involved examination of fish and crayfish distributions within habitat types at key sites, and also the measurement of hydrological characteristics within those broad habitat types present (i.e. pool and/or riffles) at each of those sites. This aimed to determine preliminary habitat preferences of each species during baseflow conditions in Milyeannup Brook.

On each sampling occasion at Mil 3 (just upstream of Brockman Hwy), Mil 4, Mil 5, and Mil 6 (limit of surface water in both 2007 and 2008), fish and freshwater crayfish densities were determined in up to three habitat types (pool and riffles where present) at each site using double pass electrofishing with each habitat sectioned off using stop nets. All fish were identified and measured to the nearest 1mm TL (fish) or OCL (crayfish) and a density determined by measuring the area of the habitat between the stop nets. Densities of each species within each habitat in baseflow conditions in 2007 and 2008 were graphically compared.

Depth profiles were taken across three cross‐sections and along one longitudinal‐section on each occasion. Mean and maximum depths of both section type in each habitat and also each habitat overall was determined and displayed graphically. The instantaneous discharge at each site (where flow was evident) was determined on both occasions via measuring channel width, depths and flows rates (using a hand‐held flow meter). Mean water temperature, conductivity, pH, dissolved oxygen, and turbidity were also determined for each site.

In order to determine whether relationships existed between the depth of baseflow habitats in Milyeannup Brook and the density of species occupying those habitats, preliminary linear regression analysis was conducted between these variables and scatter‐plots generated.

Main Channel

Freshwater Cobbler movements and environmental variables: 2005‐2008

The association between the strength of upstream and downstream Freshwater Cobbler movements and the above key environmental variables were examined. For overall sampling time analysis, all sampling occasions at all sites were included in stepwise regression analysis to determine which of the environmental variables best explained the variation in upstream or downstream Freshwater Cobbler movements in the Blackwood River main channel.

The mean upstream and downstream movements of Freshwater Cobbler in the main channel were determined for the period of lowest flow (i.e. December‐April) and their relationship to environmental variables during those periods analysed. Correlation analysis and stepwise multiple regression models were developed to determine which single or combinations of environmental variables during the major movement period best explained the most variation in upstream and downstream migrations of Freshwater Cobbler. For both of the above analyses, Shapiro‐Wilk statistical tests for normality were undertaken for each variable and all data were subsequently log‐10 transformed prior to analysis. Bi‐variate correlations between each environmental variable were calculated (Pearson’s correlation coefficient) prior to each stepwise regression analysis to initially examine possible associations between environmental variables. In the subsequent stepwise regression analyses, levels of co‐linearity between independent variables were investigated via determining condition indexes and eigenvalues. Mean velocity was consistently highly correlated with discharge and was therefore excluded from the analyses to avoid problems with co‐linearity. The more conservative, adjusted co‐efficient of determination (r2) were examined in each model as the adjusted values closely reflect the goodness of fit of the model (SPSS, 2005).

Relationship between baseflow hydrology and riffle usage

The above analyses revealed that discharge appeared to by a key variable in influencing upstream Freshwater Cobbler movement during the seasons of lowest flow (i.e. summer and early autumn, see Results); the relationship between upstream movement of Freshwater Cobbler over the two riffle zones and hydrology during baseflow was therefore determined. The month with the consistently lowest discharge (i.e. March, see Results) was chosen for this analysis in order to provide minimum flow and depth requirements.

The relationship between mean upstream movements of Freshwater Cobbler and discharge at two riffle zones in March 2006, 2007, 2008 and an additional sample in 2009 were determined using regression analysis. Mean upstream movement during each March period was plotted against discharge at those times and a number of models were tested with the highest co‐efficient of determination fitted. These models were then rearranged to determine the theoretical discharge level at which zero movement would occur; implying the minimum baseflow required for access to the riffles during baseflow.

Using the zero‐movement discharge estimates on each riffle and the WSL and cross‐sectional profiles, the minimum depth across each riffle that the Freshwater Cobbler movement would hypothetically cease was determined. This was achieved by first using the non‐linear relationships of WSL and discharge at each riffle to determine the stage heights at those zero‐movement discharges. These zero‐movement stage heights were then plotted on the three cross‐sections of each riffle zone to determine the maximum depths (deepest passage) that would be present at those minimum discharges. The shallowest maximum cross‐ sectional depth was inferred to represent the depth at which Freshwater Cobbler would cease to be able to move upstream over these riffle sections in the Blackwood River. 15

Mark‐recapture of Freshwater Cobbler

In order to investigate whether movements of this species through riffle zones are localised or associated with larger distances, a total of 437 were tagged between October and December 2005 using individually numbered t‐bar tags at each main channel site. One each subsequent sampling occasion, site of recapture was recorded for each individual.

Reproductive biology

The spawning period and length at first maturity of Freshwater Cobbler were determined in order to provide evidence of whether movements may be linked to spawning behaviour. The temporal trend in the reproductive biology of T. bostocki was determined by retaining monthly samples of females (pooled between sites). These fish were euthanased in an ice slurry, weighed to the nearest 0.01g, their gonads removed, and also weighed to the nearest 0.01g. The monthly gonadosomatic indices (GSI) of mature and immature individuals of both sexes were determined using the equation:

GSI=100(W1/W2)

Where W1 is the wet weight of the gonad and W2 is the wet somatic weight. Ovaries and testes were assigned on macroscopic appearance using the seven stages adapted from Laevastu 1965, namely: I virgin (immature), II maturing virgin/recovering, III developing, IV developed, V mature (gravid), VI ripe (spawning) and VII spent. The lengths at first maturity of female T. bostocki were determined by fitting a logistic equation to the percentage contribution made, during the spawning period, by immature and mature fish in each 10 mm length increment.

The logistic equation used to predict length at which females commenced maturation was:

1 P = 1+ exp[]− ln(19)(L − L50 ) /(L95 − L50 )

Where P = the proportion mature, L = fork length in mm, L50 and L95 are lengths in mm at which 50 and 95% of female fish reach sexual maturity, respectively, and ln is the natural logarithm. Females were classified as mature during stages III to VI because they had the potential to spawn, were spawning or had spawned.

Results and Discussion

Water quality and discharge regimes

Examination of the climatic conditions in the Blackwood River study area (Figure 1), it is evident that the 2005‐2006 sampling period was typified by above average spring 2005 to summer 2006 rainfall with a delayed onset of major winter rainfall in 2006. During the same period in 2006‐2007, the reverse occurred with a well below average spring and early summer rainfall followed by variable rainfall in later summer and autumn 2007 (Figure 2). The very low late spring and summer rainfall in the 2007‐2008 period was also notable.

The greater discharge during base flow conditions in the main channel sites in early 2006 (i.e. March, see Figures 3‐6) compared to those experienced in 2007 and 2008 were probably the result of the above average rainfall between October 2005 and January 2006. This also corresponded with much stronger movement of Freshwater Cobbler during the baseflow conditions in 2006 compared with the subsequent two years (see section on Relationship between Freshwater Cobbler and baseflow discharge).

The water temperature traces from the data loggers between 2005 and 2008 clearly indicate that most are highly associated with ambient air temperatures (Figure 8). However, along with the instantaneous water temperatures at the times of sampling in the tributaries (Figure 7), demonstrated that Milyeannup Brook maintained a less variable and lower temperature than the other tributaries (Figures 7 and 8). This is attributed to the input of the Yarragadee Aquifer groundwater that results in the buffering of the water temperature against air temperature fluctuations. That is, this system maintains cooler water temperatures during the baseflow period and is warmer during the winter period (see also section on Milyeannup Brook Baseflow Monitoring). Poison Gully, although also maintaining permanency due to aquifer discharge, does not display this buffering effect; probably due to the streams morphology in that it is a wider, shallower and more diffuse stream line which would increase the influence of air temperature.

Main channel water temperatures upstream and downstream of the major aquifer discharge zone (i.e. Denny Road and Milyeannup Pool, Figures 7 and 8) did not differ during baseflow period as may have been expected. This was probably due to the effect of external heating of the cooler aquifer water as it flows downstream offsetting the lower temperature of the aquifer water.

Conductivities in the tributary sites show that Milyeannup Brook and Poison Gully generally remained fresher than the other tributaries in baseflow conditions (see also section on Milyeannup Brook Baseflow Monitoring) (Figure 9). Those tributaries that cease to flow and pool during baseflow (i.e. St John’s Brook, Rosa Brook and McAtee Brook) showed elevated salinities during baseflow due to evapoconcentration of salt without fresh groundwater input; however, all remain fresh throughout the year. Although Rosa Brook dries and exhibits elevated salinities at the Denny Road sampling site, further upstream at the confluence of Rosa Brook and Mowen Road permanent flowing water is located. It is recommended that the Mowen Road site is sampled and compared to the Denny Road site as the permanent flow, and presumably lower salinity, provides an important habitat for the Mud Minnow (Morgan et al. 2003, 2004).

Seine/electrofishing tributary sites

Tributary fyke net sites

Main channel sites

Quigup

McAtee Bk

Rosa Brook Layman Bk Jalbarragup

Denny Rd Milyeannup Pool

Gingalup Milyeannup Brook Poison Gully

Figure 1 Sampling sites in the main channel and tributaries of the Blackwood River.

Monthly rainfall during study 200 Long term monthly rainfall (1887-2008)

150

100 Rainfall (mm) Rainfall

Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr 2005 2006 2007 2008

Month

Mean monthly maximum during study period Long term mean monthly maximum 32

26 C) o

Temperature ( Temperature 20

14 Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr 2005 2006 2007 2008 Month

Figure 2 Mean monthly rainfall (top) and maximum air temperatures (bottom) during the initial period of the study and long term averages (from Bridgetown). Data from Australian Bureau of Meteorology.

1.0 Lower Blackwood River

609-1362 Gingilup 0.9 Hut Pool Layman Brook Poison Confl 0.8 Sues Bridge 0.7 Milyeannup Confl ) 0.6

0.5 Flow (m3/s 0.4 Observed Salinity Flow (Mar2003) Flow (Mar2004) 0.3 Flow (Feb2005) Flow (Mar2006) "Limits 0.2 LBF (Mar2006) LBF (Mar2003) LBF (Mar2004) 0.1 LBF (Feb2005) flow (Feb 2007) 2008 Darradup 0.0 40 50 60 70 80 90 100 110 120 Dist from Molloy Is. (km)

Figure 3 Consecutive annual baseflow longitudinal discharge traces in the main channel of the Blackwood River in March. N.B. the relatively high baseflow discharge in March 2006 compared to 2007 and 2008. (Figure from Department of Water, Bunbury).

Total Monthly flows Blackwood River main channel

Nannup 058 140000 Darradup 025 Gingilup 041 120000 Hut 019

L 100000

80000

60000

Monthly flow M flow Monthly 40000

20000

0 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- Jan- Mar - May - Jul- Sep- Nov - Jan- Mar - May - Jul- Sep- Nov - Jan- Mar - 06 06 06 06 06 06 07 07 07 07 07 07 08 08 Date

Figure 4 Total monthly flows at sites in the main channel of the Blackwood River during the majority of the sampling period (Figure from Department of Water, Bunbury).

Total monthly summer flows Blackwood River 4000 Nannup 058 3500 Darradup 025 Gingilup 041 3000 L Hut 019 2500

2000

1500 Monthly total flow M 1000

500

0 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- 01- Jan- Feb- Mar - Apr- May - Dec - Jan- Feb- Mar - Apr- May - Dec - Jan- Feb- Mar - Apr- May - 06 06 06 06 06 06 07 07 07 07 07 07 08 08 08 08 08 Date

Figure 5 Total monthly summer flows at sites in the main channel of the Blackwood River (Figure from the Department of Water, Bunbury).

Rosa Brook 3500 Laymans Brook McAtee Brook Milyeannup Brook - upstream 3000 Milyeannup Brook - downstream

2500 /sec) 3 2000

1500

1000

Mean dischargeMean (m 500

5 5 6 7 7 7 7 7 8 05 0 06 06 06 06 v n06 y l l07 b0 r08 ct ar06 ct ne0 e p O Ja Apr06 Jun06Ju O Jan0 Apr07 Ju Oct07 Jan08 A No Dec0 Feb06M Ma Aug Sep0 Nov06Dec06 Feb0 Mar0 May0Ju Aug07Sep07 Nov07Dec07 F Mar08

Month

Figure 6 Mean discharge at tributary sites in the main channel of the Blackwood River.

Rosa Brook Laymans Brook 24 McAtee Brook Milyeannup Brook - upstream Milyeannup Brook - downstream St John Brook 22 Poison Gully

14 Temperature (°C)

5 6 6 6 7 7 7 7 7 8 06 0 0 07 0 07 07 v0 n06 b0 r06 l c06 r r y e0 g v0 n08 b0 r08 a e a ay06 u ep06 a p u a e a Oct05 J Apr06 Jun06J Oct0 Jan0 A Jul07 Oct07 J Apr08 No Dec05 F M M Aug S Nov06De Feb07M Ma Jun A Sep No Dec07 F M

Month

Rosa Camp Gingilup 26 Milyeannup pool Jalbarragup Quigup 24

16 Temperature (°C)

5 5 6 6 6 6 6 6 6 7 7 7 7 7 8 0 0 06 06 0 06 0 0 0 0 07 0 0 n0 b r r0 y0 l0 c r07 g t07 v0 n08 b ov a e p u ct e u c o a e Oct J A Jun06J O Jan Apr Jul07 O J Apr08 N Dec05 F Ma Ma Aug Sep06 Nov0D Feb07Ma MayJune07 A Sep N Dec07 F Mar08

Month

Figure 7 Mean instantaneous water temperature at sites in the tributaries (top) and main channel (bottom) of the Blackwood River.

Milyeannup Brook - Brockman Hwy 38 Rosa Brook - Denny Rd McAtee Brook - Longbottom Rd 36 Laymans Brook - Denny Rd Blackwood River- Milyeannup Pool 34 Milyeannup Brook - Blackwood Rd Blackwood River - Denny Rd 32 Blackwood River - Jalbarragup Rd Poison Gully - Blackwood Rd 30 Bridgetown mean maximim air temperature 28 26 24 22 20 18 16 14 Water temperature (°C) 12 10 8 6

2005 06 20 11/ 06 1/ 2006 1/01/ 03/ 20 1/ 2006 1/05/ 07/ 2006 006 Month 1/ 2 1/09/ 2007 07 1/11/ 20 1/01/ 2007 007 Figure 8 Water temperatures from the data loggers (logged every 3 hours) at sites1/03/ in the Blackwood River2 and its007 tributaries. N.B. the close association of water temperatures in all 1/05/ 2 sites and maximum air temperature (in Bridgetown) and cooler water temperature during1/07/ summer in Milyeannup2007 Brook.008 1/09/ 2 008 1/11/ 2 23 1/01/ 1/03/ Rosa Brook Laymans Brook McAtee Brook Milyeannup Brook - upstream 1200 Milyeannup Brook - downstream St Johns Brook Poison Gully

1000

800

600

400 Conductivity (µS/cm)

200

5 7 t0 v06 06 0 l07 t07 08 c an06eb06 ar06 ep06 ec ar07 ay u c an08eb08 ar O J Apr06 Jun06Jul06 Oct06 Jan07 Apr07 une07J O J Apr08 Nov05Dec05 F M May06 Aug06S No D Feb07M M J Aug07Sep07 Nov07Dec07 F M Month

Rosa Camp 8000 Gingilup Milyeannup Pool Jalbarragup Quigup 7000

6000

5000

4000

Conductivity (µS/cm) 3000

2000

1000

6 6 6 6 6 6 6 7 7 7 7 7 8 8 05 06 0 0 0 07 07 07 07 07 0 08 0 v b r0 n g c0 n r r e l0 p07 v b o a u e ay0 ct07o Oct05 Jan06 Apr06 J Jul06 Oct0 Ja Ap Ju O Jan Apr N Dec05 Fe M May06 Au Sep0 Nov D Feb0Ma M Jun Aug0Se N Dec0 Fe Mar08 Month

Figure 9 Mean instantaneous conductivities at sites in the tributaries (top) and main channel (bottom) of the Blackwood River. N.B. fresher conditions at the more downstream sites (i.e. Denny Road and Gingilup) during baseflow periods.

The trends in conductivity of the main channel sites clearly show the effects of the increase groundwater input due to the Yarragadee Aquifer (see Figures 8, 9 and 10) with the Denny Road baseflow conductivity in March 2007 and 2008 ~60% fresher than those upstream of the zone. This difference is even greater than that recorded during the (relatively high discharge) baseflow conditions in 2006 when a ~40% difference was recorded. The relationship between the main channel baseflow discharge and conductivity is significantly negatively related (Figure 10). This clearly demonstrates the importance of groundwater input in reducing the salinity in the main channel of the river during baseflow period when many of the tributaries cease to flow. This has implications for the seasonal habitat usage patterns of salt‐intolerant freshwater species in the Blackwood River. For example, the fact that the Mud Minnow is not found in the main channel of the Blackwood River (Beatty et al. 2006, see also Mud Minnow section in the current report) may be due to its inability to tolerate the prevailing conditions in that habitat (particularly salinity). Phillips et al. (2007) demonstrated that the Mud Minnow populations in the various tributaries of the Blackwood River have considerable genetic variability; further supporting this theory of isolation.

The trends in PH are generally to decrease during baseflow conditions compared with high‐flow periods (Figure 11). This is probably due to the increased influence of acidic tannins from riparian vegetation and salt water during reduced water levels. Figure 12 shows that dissolved oxygen levels were highly variable between sites and seasons. Generally, dissolved oxygen levels were lower during summer period.

3.8 log (cond) = 4.73-0.52*log(disch) r2 = 0.87 p = 0.00 3.7 ) -1

3.6

3.5

3.4 log10 Conductivity (µS.cm 3.3

3.2

1.8 2.0 2.2 2.4 2.6 2.8 3.0 log10 Discharge (L/sec)

Figure 10 Relationship between the baseflow discharges (i.e. in all March samples) at all sites sampled in the main channel of the Blackwood River and the mean water conductivities at those sites.

Rosa Brook Laymans Brook McAtee Brook Milyeannup Brook - upstream 9 Milyeannup Brook - downstream St John Poison Gully

6 pH

5 6 6 6 6 6 6 6 7 7 7 7 7 8 8 0 06 0 07 07 0 08 0 c0 r0 y0 l06 g v c0 y0 e g v r e p a u ct0 o e pr a n ct0 o pr Oct05 Jan06 A Jun0 J O Jan07 A Jul07 O Jan0 A Nov05D Feb0Mar06 M Au Sep06 N D Feb0Mar07 M Ju Au Sep07 N Dec07 Feb08Ma Month

Rosa Camp Gingilup 9.0 Milyeannup pool Jalbaragup Quigup 8.5

8.0

7.5 pH 7.0

6.5

6.0

5.5

5 6 6 6 6 7 7 7 7 8 06 06 06 0 07 07 07 0 08 0 08 08 c0 b r y l0 g0 n b r l0 g0 n b r r e e ar06 u ep e ar07 u ep e a Oct05 Jan06 Ap Jun06Ju Oct06 Ja Ap Ju Oct07 Ja Ap Nov05D F M Ma A S Nov06Dec0 F M May07June07 A S Nov07Dec0 F M Month

Figure 11 Mean instantaneous pH at sites in the tributaries (top) and main channel (bottom) of the Blackwood River.

18 Rosa Brook Laymans Brook McAtee Brook Milyeannup Brook - upstream 16 Milyeannup Brook - downstream St Johns Brook Poison Gully 14

Dissolved(ppm) oxygen 6

5 6 6 6 6 6 6 6 7 7 7 7 7 8 8 0 0 0 06 0 06 0 0 07 0 r0 n l v c06 n g p v0 c07 n08 b0 r08 ov05ec eb pr0 u ep o e a ct o e a e p Oct05 Jan06 A J Ju Oct0 J Apr07 Jul07 O J A N D F Ma May0 Aug06S N D Feb07Mar07 May0June07 Au Se N D F Mar0

Month

Rosa Camp 20 Gingilup Milyeannup pool Jalbaragup 18 Quigup

Dissolved oxygen(ppm) 8

6 6 6 7 7 7 7 8 05 05 06 06 06 06 0 06 0 0 07 08 08 n y0 p06 t c r07 e07 t ct eb06 ul e a ul07 ep0 eb ar08pr0 O Ja Apr0 Jun J Oc Jan Apr0 J Oc Jan A Nov05Dec F Mar06 Ma Aug06S Nov De Feb07M MayJun Aug07S Nov07Dec07 F M

Month

Figure 12 Mean instantaneous dissolved oxygen at sites in the tributaries (top) and main channel (bottom) of the Blackwood River.

Discharge measurements at the various gauging stations along with cross‐sectional discharge and depth profiles at the Denny Road and Milyeannup riffle zones in the main channel suggested that baseflow conditions occurred during March in this section of the Blackwood River (Figures 13 and 14).

Upstream 10.5 WSL March 07 - 425 L/s Stage Discharge Realationship Rosa Camp R1 WSL May 07 - 725 L/s 10.3 WSL March 08 - 468 L/s 9.4 WSL April 08 - 742 L/s y = -0.173x2 + 0.5601x + 8.9186 9.35 10.1 9.3 9.25

9.9 t 9.2 9.15 9.7 9.1 9.05 Stage Hiegh Survey height 9.5 9 9.3 8.95 8.9 9.1 8.85 0 0.2 0.4 0.6 0.8 1 1.2 1.4 8.9 Discharge m3/s 0 5 10 15 20 25 Dis t ance ( m )

Mid-riffle

Stage Discharge Realationship Rosa Camp R2 9.7 WSL March 07 - 425L/s WSL May 07 - 725 L/s 9.3 y = -0.2088x2 + 0.5794x + 8.8538 WSL March 08 - 468 L/s 9.25 9.5 WSL April 08 - 742 L/s 9.2

t 9.15 9.3 9.1 9.05 9.1 9 Stage Hiegh 8.95 Survey HeightSurvey 8.9 8.9 8.85 8.7 8.8 0 0.2 0.4 0.6 0.8 1 1.2 1.4 8.5 Discharge m3/s 0 0.4 1 1.8 2.4 3.9 4.7 6.2 7.7 9 9.7 10.1 10.7 10.9 11.9 Distance (m)

Downstream

9.7 WSL March 07 - 425 L/s Stage Discharge Realationship Rosa Camp R3 WSL May 07 - 725 L/s 9.3 WSL March 08 - 468 L/s y = -0.4634x2 + 1.054x + 8.6249 WSL April 08 - 742 L/s 9.5 9.2 9.1

9.3 t 9 8.9 9.1 8.8 Stage Hiegh

Survey HeightSurvey 8.9 8.7 8.6 8.7 8.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 8.5 Discharge m3/s 024681012 Distance (m)

Figure 13 Cross‐sectional riffle profiles during base‐flow months in 2007 and 2008 at Denny Road in the Blackwood River (Figure from Department of Water, Bunbury).

Upstream

9.9 WSL March 07 - 137 L/s Stage Discharge Realationship Milyeannup R1 9.8 WSL May 07 - 376 L/s 9.7 WSL March 08 - 142 L/s y = -0.5944x2 + 1.0464x + 9.1305 9.7 WSL April 08 - 370 L/s 9.6

9.6 9.5

9.5 9.4

9.4 9.3

9.3 Stage Hieght 9.2 Survey Height

9.2 9.1

9.1 9 0 0.2 0.4 0.6 0.8 1 1.2 9 Discharge m3/s 0123456789 Distance (m)

Mid-riffle 10 Stage Discharge Realationship Milyeannup R2 WSL March 07 - 137 L/s 9.9 WSL May 07 - 376 L/s 9.5 WSL March 08 - 142 L/s y = -0.345x2 + 0.5993x + 9.1936 9.8 WSL April 08 - 376 L/s 9.4 9.7

9.6 9.3 9.5 Stage Hieght

Survey Height Survey 9.4 9.2

9.3

9.2 9.1 0 0.2 0.4 0.6 0.8 1 1.2 9.1 Dis char ge m 3/s 02468101214 Distance (m)

Downstream 9.8 WSL March 07 - 137 L/s Stage Discharge Realationship Milyeannup R3 9.7 WSL May 07 - 376 L/s 9.3 WSL March 08 - 142 L/s y = -0.1993x2 + 0.4386x + 9.0414 WSL April 08 - 370 L/s 9.6

9.5 9.2

9.4

9.3 Stage Hieght 9.1 Survey Height 9.2

9.1 9 0 0.2 0.4 0.6 0.8 1 1.2 9 Dis char ge m 3/s 02468101214 Distance (m)

Figure 14 Cross‐sectional riffle profiles during base‐flow months in 2007 and 2008 at riffle downstream of Milyeannup Pool in the Blackwood River.

Freshwater Cobbler

Spatial and temporal patterns in Freshwater Cobbler migration

A total of 5972 Freshwater Cobbler were captured in the main channel during the study. The movement strength generally peaked in late spring and summer with considerable differences in the temporal movement patterns existing between the sites (Figure 15). The mean upstream movement of Freshwater Cobbler in all sampling months was positively associated with the mean downstream movements during those sampling times (r2=0.32, p=0.000) (Figure 16).

Of the 437 tagged Freshwater Cobbler in the main channel of the Blackwood River, a total of 86 (19.7%) were recaptured (Table 1). Of these, 68 were recaptured once, 14 twice, five three times and two were recaptured four times (Table 1). With the exception of one fish, all were caught at the initial tag‐capture site.

Table 1: Freshwater Cobbler tagged and recaptured in main channel sites of the Blackwood River. N.B. Includes % recaptured per site and % total of all recaptures when compared to total number tagged.

SITE Number # Recaptured # Recaptured # Recaptured 3 #Recaptured 4 Tagged (%) Twice times Times (%) (%) (%)

Denny Road 215 42 8 1 (19.5) (3.7) (0.5)

Milyeannup 42 7 2 Pool (16.7) (4.76)

Jalbarragup 110 17 4 4 2 (15.5) (3.6) (3.6) (1.8)

Quigup 70 2 (2.9) TOTAL 437 68 14 5 2 (15.6) (3.0) (1.1) (0.5) (%)

Freshwater Cobbler 3000 Denny Road 2500 Downstream movement 2000 Upstream movement 1500 1000

500

1400 Gingilup 1200

1000 800 600 400 200 NOT SAMPLED 2005 0 6000

5000 Milyeannup Pool

4000

3000

2000 1000 Mean number of fish number Mean 0 1400 Jalbarragup . 1200 1000 800 600

400

200

1400 Quigup 1200

1000

800

600

400

200

0 NOT SAMPLED FROM AUGUST 2006

5 5 5 6 6 6 6 6 7 7 7 7 7 7 7 7 8 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 l 0 er er er ry ch ne st er ch ay ne st er er er er ch ri ob b b ua ar Ju gu b ar M Ju gu b ob b b ar Ap ct em em br M Au em M Au em ct em em M O ov ec Fe pt pt O ov ec N D Se Se N D

Month

Figure 15 Upstream and downstream migration of Freshwater Cobbler in the Blackwood River main channel sites.

log10 (Nup+1) = 0.87*log10(dnN+1) + 0.64 r2 = 0.32 4 p = 0.000

0 log10 frequency (mean ofupstream moving fish +1)

0.0 0.5 1.0 1.5 2.0 2.5 log10 (mean frequency of downtstream moving fish +1)

Figure 16 Relationship between the mean strength of upstream versus downstream movements of Freshwater Cobbler in the Blackwood River main channel in all sampling months. N.B. Data were log10 transformed and migration number was standardised for effort; see text for details.

Relationships between Freshwater Cobbler migration patterns and environmental variables in the Blackwood River

Correlation and stepwise multiple regression analysis revealed that the upstream (r2 = 0.50, p = 0.03) and downstream (r2 = 0.52, p = 0.026) movements of Freshwater Cobbler in all main channel sites during the period of lowest flow (i.e. December to April) were most significantly explained by mean discharge at those sites during those periods (Table 2, Figure 17).

The models that gave the highest coefficients of determination for the relationship between upstream movements of Freshwater Cobbler over the two riffle sites at baseflow (i.e. March) and levels of baseflow discharge in those months were inverse polynomials and these revealed a strong association between these variables at both the Milyeannup Pool (r2 = 0.991, p = 0.004) and Denny Road riffles (r2 = 0.817, p = 0.096) (Figure 18). Using these models, the minimum discharge that Freshwater Cobbler movement would be totally precluded at the Milyeannup Pool and Denny Road riffles are estimated to be 381.5 L/sec and 101.9 L/sec, respectively. Based on this zero‐movement discharge, analysis of the riffle cross‐sections and the discharge‐stage height relationships (Figures 13 and 14), the depth across riffles when zero movement discharge would occur is 0.18 and 0.05 m for Denny Road and Milyeannup Riffle, respectively. However, those individuals that were captured moving upstream during the March 2007, and 2008 period were much smaller than those captured during 2006; when the greatest baseflow discharge levels were recorded (Figure 19).

Table 2 Correlations between overall mean upstream and downstream movements of Freshwater Cobber in the main channel sites of the Blackwood River and prevailing environmental variables during the lowest discharge period (December to April). N.B. Data were log10 transformed, * denotes correlation is significant at the 0.05 level (2‐tailed).

Downstream Upstream Discharge Temperature Conductivity pH Dissolved O2 Downstream Pearson Correlation 1

Sig. (2‐tailed)

Upstream Pearson Correlation .566 1 Sig. (2‐tailed) .143

Discharge Pearson Correlation .767(*) .756(*) 1 Sig. (2‐tailed) .026 .030

Temperature Pearson Correlation .455 .851(**) .673 1 Sig. (2‐tailed) .257 .007 .067

Conductivity Pearson Correlation ‐.747(*) ‐.502 ‐.905(**) ‐.366 1 Sig. (2‐tailed) .033 .205 .002 .373

pH Pearson Correlation ‐.193 ‐.396 ‐.288 .073 .365 1 Sig. (2‐tailed) .648 .332 .489 .863 .373

Dissolved O2 Pearson Correlation ‐.049 .332 .530 .173 ‐.515 ‐.318 1 Sig. (2‐tailed) .909 .422 .177 .683 .191 .443

Upstream movement 3.0 log10N = 2.20*log10D - 4.15 r2 = 0.50 p = 0.03

2.5

2.0

1.5 log10 frequency mean of fish

1.0 2.4 2.6 2.8 3.0 3.2 log10 mean discharge (L/sec)

Downstream movement 2.4 log10N = 1.87*log10D - 3.80 2 2.2 r = 0.52 p = 0.026 2.0

1.8

1.6

1.4

1.2

1.0

0.8

log10 frequency mean of fish 0.6

0.4

0.2 2.42.62.83.03.2 log10 mean discharge (L/sec)

Figure 17 Relationships between the mean strength of upstream movement of Freshwater Cobbler and the mean discharge in the Blackwood River main channel. N.B. Data were log10 transformed and migration number was standardised for effort, see text for details.

3.5 log10 (N+1) = 13.591 - (27.291/log10(D)) r2 = 0.991 p = 0.004 3.0

2.5

2.0

1.5

1.0

log10(n+1) frequency of mean fish 0.5

0.0 2.0 2.1 2.2 2.3 2.4 2.5 2.6

log10 Discharge (L/sec)

2.5 log10 (N+1) = 23.748 - (61.304/log10(D)) r2 = 0.817 p = 0.096 h s fi

2.0 f

1.5 requency o f

1.0 mean mean 1) n+ (

10 0.5 og l

0.0 2.60 2.65 2.70 2.75 2.80 2.85 2.90

Log10 Discharge (L/sec)

Figure 18 Relationship between mean upstream Freshwater Cobbler movement over the Milyeannup (top) Denny Road (bottom) riffles and the mean discharge at those sites during March 2006‐2009.

Freshwater Cobbler

Downstream Migration Downstream Migration 50 50 Upstream Migration Upstream Migration 2005 May October 25 25 n=26 n=31

0 0 50 50 November June n=253 n=8 25 25

0 0 50 50 December August n=283 n=255 25 25

0 0 50 2006 50 February September n=334 n=232 25 25

0 0 50 50 March October

n=550 n=86 25 25

0 0 Number of Fish Number of 50 50 June November n=21 n=169 25 25

0 0 50 50 August December n=11 n= 185 25 25

0 0 50 50 2008 September March n=97 n=116 25 25

0 0 2007 50 March 50 April n=108 n=56

25 25

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 Total Length(mm) Total Length(mm)

Figure 19 Length‐frequency of Freshwater Cobbler, differentiated by upstream and downstream movement, in the

Blackwood River main channel. N.B. the dashed line is the length at maturity (L50) of females (172mm TL).

Reproductive biology

The mean GSI of mature females of Freshwater Cobbler increased sharply between August and October; peaking in the latter month (Figure 20). From October to December the most significant decline occurred dropping from 4.94 to 1.65 between these two months, respectively; suggesting this is the peak spawning time. The GSI of males, while having far less variability than females, also peaked in October at 0.55.

The logistic curve, fitted to the percentage contribution of Freshwater Cobbler with gonads of stages III‐VII in sequential 10 mm TL increments during the spawning period, yielded a L50 of ~172 and L95 of 226 for females i.e. lengths at which 50% and 95% of the population is sexually mature (Figure 21).

Mean Gonadosomatic Indices (+1SE)

5.5 19 Month vs Female 5.0 Month vs Male

4.5 30 4.0

3.5 18 3.0

2.5 Mean GSI 2.0 61 9 1.5 13 10 18 39 1.0 68 0.5 10 3 13 10 29 20 6 0.0 2 6 5

t r r e s e e ry ry h n u b b a a rc u July g m m u u a April J n M Au ve a October J Febr Septe No December

Month

Figure 20 Mean gonadosomatic indices (GSI) (+ 1SE) for male and female Freshwater Cobbler in the main channel of the Blackwood River.

% mature (Stage III - VII) % immature (Stage I - II)

1 5 3 3 3532 5 8 6 9 7 911 18`14 12 11 11 12 687 222 100

40 Percentage (%) 30

0 100 120 140 160 180 200 220 240 260 280 300 320 340 360 Total length (mm)

Figure 21 Mean length at first maturity for female Freshwater Cobbler in the Blackwood River.

Freshwater Cobbler: summary and implications

This study has demonstrated considerable movements of T. bostocki within the main channel of the Blackwood River. The mark‐recapture program also suggested these movements were highly localised and suggested a high degree of site (possibly on the scale of individual pools) fidelity. Strengths of movements differed markedly both spatially and temporally; however, upstream movement peaked at all sites in spring and summer. Furthermore, the degree of upstream movement during the period of lowest flow (and greatest proportional contribution of groundwater to total flow) was significantly related to volume of discharge during that period at those sites. The impetuous for these considerable localised movements through riffle zones is probably due more to feeding activities rather than spawning as feeding on this habitat type has been shown to occur with other freshwater catfishes (e.g. Pylodictis olivardis, Trautman 1981, Hatcheria macraei Barriga and Battini 2009) and this study demonstrated a wide size range (including smaller immature individuals) accessed the riffles at those times. However, for this to be confirmed, the feeding ecology of the species needs to be determined along with precise identification of its spawning habitats.

The significance of the considerable upstream movements of Freshwater Cobbler in terms of sustaining the population requires further validation (e.g. by comparing levels of recruitment, feeding and reproductive ecology of this and other populations), however, it is proposed that this relatively large‐bodied species could be an appropriate indicator of baseflow river connectivity throughout south‐western Australia given (Morgan et al.1998). The baseflow models presented here may also be used to set minimum baseflow discharges required for riffle connectivity for this species. For example, the current study suggests that upstream movement of Freshwater Cobbler during March would be prevented at ~102 L/sec (5cm depth) and 381 L/sec (19 cm depth), for the riffles upstream and downstream of the major zone of groundwater discharge, respectively. Based on these lower limits, reductions of ~33% and ~8% reductions from the relatively low March 2007 discharges recorded at Milyeannup Pool and Denny Road riffles, respectively, would prevent any upstream Freshwater Cobbler moving over these riffle zones. As the baseflow discharge rates in this section of the Blackwood River (i.e. Darradup and Gingalup gauging stations) are dependent on the rainfall from the previous 12 month period and abstraction rates (Golder and Associates 2008), the levels of abstraction rates should be set to ensure the above minimum discharge rates are exceeded to ensure riffle access is maintained for this large bodied species.

However, these preliminary minimum estimates are for zero movements and it can be seen from the length‐ frequencies of the relative few Freshwater Cobbler captured moving over these two riffles in 2007 and 2008 that the sizes were relatively small (dominated by juveniles 40‐100 mm TL) compared to the greater number that moved over them in the relatively high‐flow event in March 2006 (no fish under 100 mm TL, dominated by mature adults 180‐340 mm TL) (Figure 10). This suggests that larger, mature Freshwater Cobbler may be inhibited from upstream movement through these riffle zones at a discharge, and associated minimum depths, considerably greater than the estimates in Table 2.

The relationships between Freshwater Cobbler movements through groundwater‐maintained riffle zones demonstrated here could be further validated by ongoing monitoring of this population during baseflow and prevailing hydrology at these sites. A tracking program (using acoustic and radio‐tracking techniques) of Freshwater Cobbler at key riffle sites would also provide fine‐scale information on their habitat use and requirements. Furthermore, understanding spatial and temporal patterns of feeding and reproductive ecology would also enable a better understanding of the purpose of these movements during baseflow conditions and their significance in maintaining populations of this species in the rivers of south‐western Australia.

Western Minnow

The Western Minnow was captured at the majority of sites sampled on most occasions, with large numbers recorded in both the main channel sites and in the tributaries. This widespread distribution, being present in nearly all habitats sampled, reflects this species tolerance to a wide range of salinities; having previously been recorded in salinities up to ~24 ppt or ~two thirds the salinity of seawater (Morgan and Beatty 2004).

However, recent rapid change salinity trials on the species from the Blackwood River have revealed a LD50 (length at 50% of individuals showed severe stress that would lead to death) at ~14 ppt (Beatty et al. 2008). Furthermore, larval stages of the species may have an even lower tolerance to salinity.

There were limited movements of Western Minnow in the most upstream main channel sites (i.e. Jalbarragup and Quigup) compared to the more downstream sites(i.e. Denny Road, Gingilup and Milyeannup Pool) and the upstream movement of Western Minnow was generally strongest during winter of each year (Figure 22). The majority of these fish were large adults (>60 mm TL) that were likely to be moving as a precursor to spawning (Figure 23).

4000 3500 Denny Road 3000

2500 Downstream movement 2000 Upstream movement

1500

1000

500

4000

3500 Gingalup 3000

2500

2000

1500

1000

500

1000 Milyeannup Pool 800

600

400

200 Mean number of fishnumber Mean

1000

800 Jalbarragup

600

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* 0

250 Quigup 200

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5 05 05 6 6 6 6 06 7 7 7 7 07 7 07 07 8 8 8 8 08 08 08 9 9 09 09 0 0 0 0 0 0 0 0 0 0 0 l 0 0 0 0 0 t r er er ry h e st er h y e st er r er er h ri e st er er er h y s er be b b a rc n u b rc a n u b be b b rc p n u b b b rc a u b o u a u g a M u g o a A u g a M g ct em em br M J u em M J u em ct em em M J u em em em M u em O v c e A t A t O v c A t v c /A t o e F ep ep o e ep o e ly ep N D S S N D S N D Ju S

Month

Figure 22 Upstream and downstream movement of Western Minnow in the Blackwood River main channel.

Western Minnow

Downstream Migration 20 Downstream Migration 60 Upstream Migration Upstream Migration 50 15 May 2005 40 October 10 30 n=255 n=37 20 5 10 0 0 20 20 November June 15 15 n=2 n=58 10 10

5 5

0 0 20 20 December August 15 15 n=4 n=70 10 10

5 5

0 0 20 2006 20 February September 15 15 n=5 n=31 10 10

5 5

0 0 20 20

15 March 15 October n=17 n=36 10 10

5 5

0 0 Number of Fish of Number 60 20 50 June 15 November 40 n=193 n=77 30 10 20 5 10 0 0 60 20 50 August 15 December 40 n=177 n= 10 30 10 20 5 10 0 0 20 40 2008 March 15 September 30 n=140 n=37 10 20

5 10

0 2007 0 20 March 40 April 15 n=96 30 n=117

10 20

5 10

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 23 Length‐frequency histograms, differentiated by upstream and downstream movement, of the Western Minnow in the Blackwood River main Channel.

The migration pattern of the Western Minnow within tributaries exhibited considerable interannual variation (Figures 24‐28). Migration within the perennial Milyeannup Brook occurred at least one month each year in than in Rosa Brook (Figure 24). For example, considerable upstream movements occurred in June each year within the perennial Milyeannup Brook that were not yet occurring in Rosa Brook or McAtee at those times. In Milyeannup Brook there were considerable downstream movements in late spring and early summer (Figure 24).

Examination of length‐frequency histograms of fish caught in main channel sites compared to tributary sites again revealed that the vast majority of Western Minnows captured less than 40 mm TL were only found within the tributaries (Figures 25‐28). This, in combination with the strong upstream migration of adults prior to the known spawning period (i.e. winter/early spring) strongly suggests that breeding takes place within tributaries and that these habitats are therefore vital spawning areas for this species.

The upstream and downstream migration of the Western Minnow in the tributaries were both previously found to be positively correlated with the mean discharge from the tributaries during the major flow period (Beatty et al. 2006). With the addition of the 2007 migration period, this relationship was still evident; however, no longer significant at p < 0.05 (although upstream was significant at p < 0.1, and downstream at p = 0.12, see Figures 29, 30, Table 3).

The strength of upstream and downstream movement of the Western Minnow during this major migration period in tributaries was positively and significantly related (r2 = 0.71, p = 0.009, Figure 31). This indicates that upstream movement of Western Minnows into tributaries can be used to predict the subsequent downstream movement of the species; that is, the return of those mature individuals moving back down into the main channel of the Blackwood River and also the subsequent degree of downstream recruitment of juveniles back into the Blackwood River.

600 Rosa Brook

500 Downstream movement Upstream movement 400

300

200

100

0 NF NF NF NF

600 Layman Brook 500

400

300

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600 Milyeannup Brook

Mean number of number fishMean 500

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100

600 McAtee Brook 500

400

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5 5 5 6 6 6 6 6 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 r r r y t r t r r r r l t r r r t r e e e r h e s e h y e s e e e e h ri e s e e e h y s e b b b a rc n u b rc a n u b b b b rc p n u b b b rc a u b o u a u g a M u g o a A u g a M g t m m r J u m J u m t m m J u m m m u m c e e b M A te M A te c e e M A te e e M A te O v c e O v c v c / o e F p p o e p o e ly p N D e e N D e N D u e S S S J S Month

Figure 24 Upstream and downstream movement of Western Minnow in the tributaries.

Western Minnow

Downstream Migration Downstream Migration 15 15 Upstream Migration Upstream Migration 2005 May 10 10 October n=0 n=16 5 5 NOT FLOWING 0 0 15 15 November June 10 n=54 10 n=11

5 5

0 0 150 15 December August 100 n=310 10 n=3

50 5

0 0 2006 15 15 February September

10 n=0 10 n=4

5 5 NOT FLOWING 0 0 15 20

March 15 October 10 n=0 n=65 Number of Fish 10 5 5 NOT FLOWING 0 0 15 20 November June 15 10 n=17 n=42 10 5 5

0 0 15 30 August December 10 20 n=46 n=85

5 10

0 0 40 15 2008 March 30 September 10 n=0 n=96 20 5 10 NOT FLOWING 0 0 2007 15 March 15 April n=0 n=0 10 10

5 5 NOT FLOWING NOT FLOWING 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 25 Length‐frequency histograms, differentiated by upstream and downstream movement, of Western Minnow in Rosa Brook.

Western Minnow

Downstream Migration Downstream Migration 150 20 Upstream Migration Upstream Migration 15 May 100 2005 October n=54 10 n=339 50 5

0 0 100 20 80 November June 15 n=306 n=66 60 10 40 20 5

0 0 20 40 August 15 December 30 n=117 n=163 10 20

5 10

0 0 2006 20 20 February September 15 n=34 15 n=16

10 10

5 5

0 0 20 60 50 15 March October 40 n=13 n=236 10 30 20 5 10 0 0

Number of Fish 100 20 November 80 June 15 60 n=241 n=26 10 40 20 5 0 0 60 20 50 December August 15 40 n=162 n=103 30 10 20 5 10 0 0 40 20 2008 March 30 September 15 n=70 n=169 20 10

10 5

0 0 2007 20 March 40 April n=104 15 n=40 30

10 20

5 10

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 26 Length‐frequency histograms, differentiated by upstream and downstream movement, of Western Minnow in Milyeannup Brook.

Western Minnow

Downstream Migration Downstream Migration 20 10 Upstream Migration Upstream Migration 15 2005 8 May October 6 10 n=0 n=60 4 5 2 0 0 NOT SAMPLED 10 10 November June 8 8 n=24 n=0 6 6 4 4 2 2 0 0 10 10 August 8 December 8 n=0 n=50 6 6 4 4 2 NOT SAMPLED 2 0 0 2006 10 10 February September 8 8 n=0 n=41 6 6 4 4 2 NOT SAMPLED 2 0 0 10 10 8 March 8 October 6 n=0 6 n=43 4 4

Number of Fish of Number 2 2 NOT SAMPLED 0 0 10 10 8 June 8 November 6 n=0 6 n=3 4 4 2 2 0 0 10 10 8 August 8 December 6 n=22 6 n= 0 4 4 2 2 NOT SAMPLED 0 0 10 10 2008 March 8 September 8 6 n=0 6 n=38 4 4 2 2 NOT SAMPLED 0 0 2007 10 March 10 April 8 n=0 8 n=0 6 6 4 4 2 2 NOT SAMPLED NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 27 Length‐frequency histograms, differentiated by upstream and downstream movement, of Western Minnow in Layman Brook.

Western Minnow

Downstream Migration Downstream Migration 30 15 Upstream Migration Upstream Migration 25 2005 May 20 10 October 15 n=0 n=31 10 5 5 NOT SAMPLED 0 0 30 15 25 November June 20 n=68 10 n=31 15 10 5 5 0 0 15 15 December August 10 n=37 10 n=6

5 5

0 2006 0 15 15 February September

10 n=0 10 n=6

5 NOT SAMPLED 5

0 0 15 15 March October 10 10 n=0 n=31

5 5 NOT SAMPLED Number of Fish 0 0 15 15 June November 10 10 n=10 n=57

5 5

0 0 30 15 25 August December 20 10 n=99 n=5 15 10 5 5 0 0 30 15 2008 25 September March 10 20 n=0 n=148 15 10 5 5 NOT SAMPLED 0 2007 0 15 March 15 April n=0 n=0 10 10

5 5 NOT SAMPLED NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 28 Length‐frequency histograms, differentiated by upstream and downstream movement, of Western Minnow in McAtee Brook.

1.3 log10N = 0.24*log10D + 1.00 r2 = 0.44 1.2

1.1

1.0

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-1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

3 log10 mean discharge (M /sec)

Figure 29 Relationship between the mean strength of upstream migration of Western Minnows within the major flow period (August and December 2005/06‐2007) and the mean discharge in the four tributaries during that period. N.B. Data were log10 transformed and migration was standardised for effort, see text for details.

log10N = 0.47*log10D + 1.55 2.0 r2 = 0.50

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-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2

3 log10 mean discharge (M /sec)

Figure 30 Relationship between the mean strength of downstream migration of Western Minnows within the major flow period (August to December 2005/06‐2007) and the mean discharge in the four tributaries during that period. N.B. Data were log10 transformed and migration was standardised for effort, see text for details.

log10N = 0.54*log10O + 0.20 1.3 2 r2 = 0.71

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0.6 log10 mean frequencylog10 mean offish upstream

0.5

0.6 0.8 1.0 1.2 1.4 1.6 1.8 log10 mean frequency of fish downstream

Figure 31 Relationship between the mean upstream and downstream migration of Western Minnows in the four tributaries within the major flow period (August to December 2005/06‐2007) N.B. Data were log10 transformed and migration was standardised for effort, see text for details.

Table 3 Correlations between upstream and downstream movement of Western Minnows in the tributaries of the Blackwood River and prevailing environmental variables during the major migration period. N.B. Data were log10 transformed, * denotes correlation is significant at the 0.05 level ** at 0.01 level (2‐ tailed).

Log Log Downstream Log NTU temperature conductivity Log pH Log O2 Log discharge movement

Log conductivity Pearson Correlation .560

Sig. (2‐tailed) .149

Log pH Pearson Correlation .127 ‐.311

Sig. (2‐tailed) .764 .453

Log O2 Pearson Correlation .022 .301 ‐.580

Sig. (2‐tailed) .958 .469 .132

Log discharge Pearson Correlation .140 .731 .022 ‐.174

Sig. (2‐tailed) .765 .062 .963 .709

Log NTU Pearson Correlation .292 .951(*) ‐.311 ‐.033 .999(*)

Sig. (2‐tailed) .708 .049 .689 .967 .023

Log downstream Pearson Correlation ‐.251 .453 ‐.419 .017 .708 .465 movement

Sig. (2‐tailed) .549 .260 .301 .968 .075 .535

Log upstream Pearson Correlation ‐.345 .220 ‐.265 ‐.016 .666 .045 .841(**) movement

Sig. (2‐tailed) .402 .601 .527 .971 .102 .955 .009

* Correlation is significant at the 0.05 level (2‐tailed).

** Correlation is significant at the 0.01 level (2‐tailed).

Mud Minnow

The Mud minnow was captured in relatively low numbers and was only captured in tributary sites (Figure 32). In the current study, it was recorded in Poison Gully, Milyeannup Brook, Rosa Brook and McAtee Brook. It is also known from Rosa Brook and Red Gully (Morgan and Beatty 2005). Phillips et al. (2007) found evidence that there are considerable genetic differences between these tributaries suggesting that the populations do not readily mix. They also found that Red Gully had the greatest genetic diversity of any population examined. The current study lends support to those findings and the salinity tolerance and habitat preferences of the species require determination to elucidate the mechanism by which the main channel of the Blackwood River is preventing mixing of those populations.

This species is known to have a one year lifecycle (Pen et al. 1991) and in the case of Rosa Brook, the breeding period is between August and October (Morgan et al. 2004). While the overall numbers of Mud Minnows captured was low, a large downstream migration of recently metamorphosed juvenile Mud Minnows occurred in Milyeannup Brook during October and November 2005 and again in October 2007 suggesting this to be an important breeding habitat for the species (Figures 32 and 33).

30 Rosa Brook

25 Downstream movement 20 Upstream movement

30 Layman Brook 25

350 345 Milyeannup Brook 340 335

Mean number of fish number Mean 330 325 320 315 310 305 300

30 McAtee Brook

Month

Figure 32 Upstream and downstream movement of Mud Minnow in the tributaries.

Mud Minnow

Downstream Migration Downstream Migration 20 20 Upstream Migration Upstream Migration 15 2005 15 October May 10 10 n=15 n=0 5 5

0 0 20 20 November June 15 n=18 15 n=0 10 10

5 5

0 0 20 20 December August 15 15 n=0 n=1 10 10

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0 0 20 2006 20 February September 15 n=3 15 n=1

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0 0 Number of Fish Number of 20 20 November 15 June 15 n=0 n=0 10 10

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0 0 20 20 December 15 August 15 n=1 n=0 10 10

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0 0 20 20 2008 15 September 15 March n=0 n=0 10 10

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0 0 20 2007 20 March April 15 15 n=0 n=0 10 10

5 5

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 33 Length‐frequency histograms, differentiated by upstream and downstream movement, of Mud Minnow in Milyeannup Brook.

Balston’s Pygmy Perch

Balston’s Pygmy Perch is listed as Vulnerable under the EPBC Act and listed as Schedule 1 at State level (Wildlife Conservation Act, 1950) (Morgan 2009). This study has demonstrated that Milyeannup Brook is the only breeding habitat for this species in the Blackwood River catchment; probably due to the consistency of suitable available habitat facilitated by the permanency of flow due to groundwater discharge in this system. Much of the upper catchment of the Blackwood River is now unsuitable for this endangered species due to secondary salinisation. Acute salinity trials revealed that this species has an acute tolerance of ~8 ppt; compared with ~14 ppt for Western Minnow and Western Pygmy Perch (Beatty et al. 2008). Although there are areas upstream of the current study area that have salinities less than 8ppt, the tolerance of earlier life history stages of all of these species (i.e. larvae) is as yet unknown and would probably be lower than the acute tolerance of the adults (Beatty et al. 2008).

This species was captured on 25 sampling months in Milyeannup Brook. The large downstream movement of juveniles annually only in Milyeannup Brook (Figures 34 and 35) demonstrates this tributary as the breeding habitat for the species. During 2007 and 2008 larger numbers were captured in the main channel than in the previous year. This highlights the importance of the long‐term sampling that has been undertaken in this study as it allows quantification of interannual variations in migration patterns. The vast majority of these fish were captured in the zone of Yarragadee Aquifer intrusion into the main channel (i.e. Milyeannup Pool (below the mouth of Milyeannup Brook) and Gingilup) and analysis of the population structure confirms these individuals correspond to the age cohorts moving from Milyeannup Brook into the main channel at those times (Figures 36 and 37). These data show that Balston’s Pygmy species utilises the main channel within the major groundwater intrusion zone downstream from Milyeannup Brook.

100 Rosa Brook

80 Downstream movement Upstream movement

100 Layman Brook

10000 Milyeannup Brook

8000 Mean numberMean of fish

6000

4000

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Figure 34 Upstream and downstream movement of Balston’s Pygmy Perch in the tributaries.

20 20 150 15 2005 15 May 100 October n=3 10 10 2008 n=5 50 June 5 5 n=0 0 0 0 120 120 100 100 November June 100 80 August 80 n=270 80 n=83 n=24 60 60 60 40 40 40 20 20 20 0 0 0 60 120 60 August 50 December 100 50 September 40 n=132 80 n=171 40 n=20 30 60 30 20 40 20 10 20 10 0 0 0 20 2006 60 November February 20 September 50 15 n=7 15 n=8 40 n=158 10 10 30 20 5 5 10 0 0 0 20 20 60 50 15 March 15 October December 40 n=18 n=0 n=144 10 10 30 20 5 5 10 0 0 0

Number ofFish 20 60 100 50 November 80 15 June 2009 40 March n=5 n=114 60 10 30 40 n=71 20 5 20 10 0 0 0 60 20 60 50 December 50 August 15 May 40 40 n=123 n=33 n=20 30 10 30 20 20 5 10 10 0 0 0 20 20 2008 60 March 50 July/August September 15 15 40 n=17 n=41 n=169 10 10 30 20 5 5 10 0 0 0 2007 September 60 20 March 20 April 50 n=47 n=4 15 n=18 15 40 30 10 10 20 5 5 10 0 0 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4 5 5 6 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 0 51 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4 5 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4 5 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length (mm)

Figure 35 Length‐frequencies of Balston’s Pygmy Perch, differentiated by upstream and downstream movement, in Milyeannup Brook between October 2005 and September 2009.

Balston's Pygmy Perch

100 Denny Road

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Month

Figure 36 Upstream and downstream migration of Balston’s Pygmy Perch in the Blackwood River main channel.

Downstream Migration 20 20 20 Upstream Migration 15 2005 15 May 15 2008 October n=4 June 10 10 10 n=0 n=0 5 5 5

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0 0 0 2006 40 20 20 February September November 15 30 n=0 15 n=0 n=119 20 10 10 10 5 5 0 0 0 20 20 20 December 15 March 15 October 15 n=0 n=0 n=2 10 10 10

5 5 5 Number of fish 0 0 0 20 20 20 November 2009 15 June 15 15 March n=0 n=22 10 10 10 n=4

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0 0 0 20 20 20 December May 15 August 15 15 n=2 n=5 n=0 10 10 10

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10 10 10

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0 0 0 0 5 0 5 0 5 0 5 0 5 0 5 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 0 51015202530354045505560657075808590950 0 1 1 2 2 3 3 4 4 5 5 6 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4 5 5 6 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4 5 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length (mm)

Figure 37 Length‐frequencies of Balston’s Pygmy Perch, differentiated by upstream and downstream movement, in the Blackwood River main channel between October 2005 and September 2009.

Western Pygmy Perch

Western Pygmy Perch was recorded in the majority of sampling occasions moving within Rosa Brook, Milyeannup Brook and McAtee Brook and was absent from Layman Brook (Figure 38). The species was also recorded moving in the main channel of the Blackwood River at the more downstream sites in spring and early summer in 2007 and 2008 (Figure 39). This movement activity in tributary sites peaked in late winter and early spring which corresponds to its breeding period and the greatest movement was recorded in spring 2008. Migration strength was greatest within Rosa Brook; which appeared to support the largest population of Western Pygmy Perch of any system. The majority of movement within the main channel was in a downstream direction, however, upstream movement was recorded during the period of low flow in summer 2008/2009. In contrast to other tributaries, within the perennial Milyeannup Brook, there continued to be upstream and downstream migrations throughout summer and early autumn; facilitated by the continuation of flows in this system resulting from direct groundwater discharge (Figure 38).

As was found with the Western Minnow, mean upstream and downstream movement of this species during the major migratory periods was significantly (p = 0.032) positively related (Figure 40).

From the length‐frequency distributions in Rosa, McAtee and Milyeannup Brooks, the species clearly breeds in these systems as evidenced by downstream movements of juveniles in these tributaries but not the main channel (Figures 41‐44). Salinity trials (Beatty et al. 2008) found that the adults of the species are

as tolerant as Western Minnow to sudden changes in salinity (LD50 = ~14ppt). The continued presence of the species in the main channel confirms that environmental conditions (particularly salinity) in this section of the river continue to be within its tolerance levels and enables it utilise this habitat; however, it breeds within the tributary habitats.

500 Rosa Brook 450

400 Downstream movement 350 Upstream movement 300 250 200 150 100 50 0 NF NF

250 Layman Brook 200

150

100

500 Mean Mean ofnumber fish 450 Milyeannup Brook 400 350 300 250 200 150 100 50 0

250 McAtee Brook

200

150

100

5 5 5 6 6 6 6 6 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 r r r y t r t r r r r l t r r r t r e e e r h e s e h y e s e e e e h ri e s e e e h y s e b b b a rc n u b rc a n u b b b b rc p n u b b b rc a u b o u a u g a M u g o a A u g a M g t m m r J u m J u m t m m J u m m m u m c e e b M A te M A te c e e M A te e e M A te O v c e p p O v c p v c / p o F e e e o ly e N De No De N De u S S S J S Month

Figure 38 Upstream and downstream migration of Western Pygmy Perch in the tributaries.

600 Denny Road 500

400 Downstream movement Upstream movement 300

200

100

400

350 Gingalup

300

250

200

150

100

300

250 Milyeannup Pool

200

150

100

50 Mean numberMean of fish 0 300 Jalbarragup 250

200

150

100

300 Quigup

250

200

150

100

9 5 05 05 6 6 6 6 06 7 7 7 7 07 7 07 07 8 8 8 8 08 08 08 9 9 0 09 0 0 0 0 0 0 0 0 0 0 0 l 0 0 0 0 0 t r er er ry h e st er h y e st er r er er h ri e st er er er h y s er be b b a rc n u b rc a n u b be b b rc p n u b b b rc a u b o ru a Ju g a M Ju g o a A Ju g a M g ct em em b M u em M u em ct em em M u em em em M u em O v c e A t A t O v c A t v c /A t o e F ep ep o e ep o e ly ep N D S S N D S N D Ju S Month

Figure 39 Upstream and downstream migration of Western Pygmy Perch in the Blackwood River main channel.

log10Up = 1.21*log10Dn - 0.48 r2 = 0.63 2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0 log10 mean frequencylog10 mean of fishupstream

-1.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 log10 mean frequency of fish downstream

Figure 40 Relationship between the mean upstream and downstream migration of Western Pygmy Perch in the four tributaries within the major flow period. N.B. Data were log10 transformed and migration was standardised for effort, see text for details.

Western Pygmy Perch

Downstream Migration Downstream Migration 10 10 Upstream Migration Upstream Migration 8 2005 8 6 October 6 May 4 n=19 4 n=0 2 2 NOT SAMPLED 0 0 10 15 8 November June n=18 n=27 6 10 4 5 2

0 0 70 10 60 December 8 August 50 n=196 n=9 40 6 30 4 20 10 2 0 0 10 2006 10 February 8 8 September n=0 n=20 6 6 4 4 2 2 NOT SAMPLED 0 0 10 30 8 March 25 October 20 6 n=0 15 n=84 4 10 2 5 0 NOT SAMPLED 0

Number of Fish 70 30 60 June 25 November 50 20 40 n=138 n=84 15 30 20 10 10 5 0 0 15 30 August 25 December 10 20 n=27 n=122 15 5 10 5 0 0 10 10 2008 8 September 8 March 6 n=23 6 n=0 4 4 2 2 0 0 NOT SAMPLED 10 2007 10 March April 8 8 n=0 n=0 6 6 4 4 2 NOT SAMPLED 2 NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Total Length(mm)1 1 1 1 1 1 1 Total Length(mm)

Figure 41 Length‐frequency histograms, differentiated by upstream and downstream movement, of Western Pygmy Perch in Rosa Brook.

Western Pygmy Perch

Downstream Migration Downstream Migration 10 10 Upstream Migration Upstream Migration 8 2005 8 6 October 6 May 4 n=11 4 n=6 2 2 0 0 10 10 November 8 8 June n=6 n=9 6 6 4 4 2 2 0 0 15 10 December 8 August 10 n=29 n=1 6

5 4 2 0 0 10 2006 10 February September 8 8 n=13 n=2 6 6 4 4 2 2 0 0 15 10 March 8 October 10 n=39 6 n=3 5 4 2 0 0 Number of Fish 10 10 8 June 8 November 6 n=6 6 n=10 4 4 2 2 0 0 10 10 8 August 8 December 6 n=5 6 n=41 4 4 2 2 0 0 10 10 2008 8 September 8 March 6 n=8 6 n=26 4 4 2 2 0 0 10 2007 10 March April 8 8 n=37 n=28 6 6 4 4 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 42 Length‐frequency distributions, differentiated by upstream and downstream movement, of Western Pygmy Perch in Milyeannup Brook.

Western Pygmy Perch

Downstream Migration Downstream Migration 10 10 Upstream Migration Upstream Migration 8 2005 8 6 October 6 May 4 n=12 4 n=0 2 2 NOT SAMPLED 0 0 20 30 November June 15 n=53 20 n=64 10 10 5

0 0 10 10 August 8 December 8 n=19 n=2 6 6 4 4 2 2 0 2006 0 10 10 February September 8 8 n=0 n=1 6 6 4 4 2 2 NOT SAMPLED 0 0 10 20 8 March 15 October 6 n=0 n=85 10 4 2 5 NOT SAMPLED 0 0 Number of Fish 10 10 8 June 8 November 6 n=18 6 n=1 4 4 2 2 0 0 50 10 40 August 8 December 30 n=155 6 n=32 20 4 10 2 0 0 10 20 2008 8 15 September March 6 n=34 n=0 10 4 5 2 NOT SAMPLED 0 0 2007 10 10 March April 8 8 n=0 n=0 6 6 4 4 2 2 NOT SAMPLED NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 43 Length‐frequency distributions, differentiated by upstream and downstream movement, of Western Pygmy Perch in McAtee Brook.

Western Pygmy Perch

Downstream Migration Downstream Migration 10 10 Upstream Migration Upstream Migration 8 2005 8 6 October 6 May 4 n=4 4 n=3 2 2 0 0 10 10 November June 8 8 n=2 n=0 6 6 4 4 2 2 0 0 10 10 8 December 8 August 6 n=9 6 n=26 4 4 2 2 0 0 2006 10 10 February September 8 8 n=0 n=3 6 6 4 4 2 2 0 0 10 10 8 March 8 October 6 n=1 6 n=12 4 4 2 2 0 0 Number of Fish 10 20

8 June 15 November 6 n=13 n=49 10 4 2 5 0 0 10 20

8 August 15 December 6 n=0 n= 36 10 4 5 2 0 0 10 10 2008 8 September 8 March 6 n=0 6 n=4 4 4 2 2 0 0 2007 10 March 10 April 8 8 n=16 n=0 6 6 4 4 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Total Length(mm)1 1 1 1 1 1 1 Total Length(mm)

Figure 44 Length‐frequency distributions, differentiated by upstream and downstream movement, of Western Pygmy Perch in the Blackwood River main channel.

Nightfish

The Nightfish was captured within all tributaries sampled and also within each main channel site (Figures 45‐51). However, the species appears to be reliant on tributary habitats for breeding with juveniles almost exclusively only being recorded from those systems (Figures 46‐49).

The Nightfish bred annually in Layman Brook as indicated by an annual downstream movement of juveniles in November suggesting a spawning in late winter early spring (Figures 45 and 48). This annual recruitment of juveniles was also recorded to a lesser degree in Rosa, Milyeannup and McAtee Brooks. The downstream juvenile migration also corresponds to a reduction in discharge from these tributaries.

Unlike the Western Minnow and Western Pygmy Perch, the mean upstream and downstream movement of this species during the major migratory periods was not significantly related. This suggests that greater strength of upstream movement of mature fish does not necessarily result in higher downstream movement of recruits (Table 6).

350 Rosa Brook 300 Downstream movement 250 Upstream movement 200

150

100

350 Layman Brook 300

250

200

150

100

350

300 Milyeannup Brook Mean number offish 250

200

150

100

350 McAtee Brook 300

250

200

150

100

5 5 5 6 6 6 6 6 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 r r r y t r t r r r r l t r r r t r e e e r h e s e h y e s e e e e h ri e s e e e h y s e b b b a rc n u b rc a n u b b b b rc p n u b b b rc a u b o u a u g a M u g o a A u g a M g t m m r J u m J u m t m m J u m m m u m c e e b M A te M A te c e e M A te e e M A te O v c e p p O v c p v c / p o e F e e o e e o e ly e N D N D N D u S S S J S Month

Figure 45 Upstream and downstream migration of Nightfish in the tributaries.

Nightfish

Downstream Migration Downstream Migration 5 5 Upstream Migration Upstream Migration 4 2005 4 3 October 3 May 2 n=8 2 n=0 1 1 0 0 NOT SAMPLED 5 5 November June 4 4 n=2 n=10 3 3 2 2 1 1 0 0 150 5 December 4 August 100 n=198 3 n=8

50 2 1 0 0 2006 5 5 February September 4 4 n=0 n=0 3 3 2 2 1 1 NOT SAMPLED 0 0 5 5 4 March 4 October 3 n=0 3 n=7 2 2 1 1 0 NOT SAMPLED 0

Number Fish of 10 5 8 June 4 November 6 n=12 3 n=3 4 2 2 1 0 0 5 15 4 August December 10 3 n=9 n=33

2 5 1 0 0 5 5 2008 4 September 4 March 3 3 n=3 n=0 2 2 1 1 NOT SAMPLED 0 0 2007 5 March 5 April 4 n=0 4 n=0 3 3 2 2 1 NOT SAMPLED 1 NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 46 Length‐frequency histograms, differentiated by upstream and downstream movement, of Nightfish in Rosa Brook.

Nightfish

Downstream Migration Downstream Migration 5 5 Upstream Migration Upstream Migration 4 2005 4 May 3 October 3 n=3 2 n=0 2 1 1 0 0 5 5 November June 4 4 n=0 n=3 3 3 2 2 1 1 0 0 150 30 December 25 August 100 n=190 20 n=112 15 50 10 5 0 0 2006 5 5 February September 4 4 n=7 n=0 3 3 2 2 1 1 0 0 5 5 4 March 4 October 3 n=20 3 n=12 Number of Fish of Number 2 2 1 1 0 0 5 5 4 June 4 November 3 n=2 3 n=4 2 2 1 1 0 0 5 10 4 August 8 December 3 n=4 6 n=25 2 4 1 2 0 0 5 5 2008 March 4 September 4 3 n=4 3 n=12 2 2 1 1 0 0 2007 10 March 10 April 8 n=16 8 n=13 6 6 4 4 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 47 Length‐frequency histograms, differentiated by upstream and downstream

movement, of Nightfish in Milyeannup Brook

Nightfish

Downstream Migration Downstream Migration 10 10 Upstream Migration Upstream Migration 8 2005 8 6 October 6 May 4 n=3 4 n=0 2 2 0 0 NOT SAMPLED 10 10 November June 8 8 n=2 n=0 6 6 4 4 2 2 0 0 200 10

150 December 8 August n=366 6 n=23 100 4 50 2 0 0 2006 10 10 February September 8 8 n=0 n=7 6 6 4 4 2 2 0 NOT SAMPLED 0 10 10 8 March 8 October 6 n=0 6 n=21 4 4 2 2 0 NOT SAMPLED 0 Number Fish of 10 50 8 June 40 November 6 n=0 30 n=59 4 20 2 10 0 NOT SAMPLED 0 10 10 8 August 8 December 6 n=0 6 n=0 4 4 2 2 NOT SAMPLED 0 0 10 10 2008 8 September 8 March 6 6 n=3 n=0 4 4 2 2 NOT SAMPLED 0 0 2007 10 March 10 April 8 8 n=0 n=0 6 6 4 4 2 NOT SAMPLED 2 NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 48 Length‐frequency histograms, separated by upstream and downstream migration, of Nightfish in Layman Brook.

Nightfish

Downstream Migration Downstream Migration 5 5 Upstream Migration Upstream Migration 4 4 2005 3 October 3 May 2 n=1 2 n=0 1 1 0 0 NOT SAMPLED 5 5 4 November 4 June n=1 n=12 3 3 2 2 1 1 0 0 5 5 4 December 4 August n=9 3 3 n=2 2 2 1 1 0 0 5 2006 5 February September 4 4 n=0 n=0 3 3 2 2 1 1 0 NOT SAMPLED 0 5 5 4 4 October March 3 3 n=0 n=4

NumberFish of 2 2 1 1 NOT SAMPLED 0 0 5 5 4 June 4 November 3 n=16 3 n=3 2 2 1 1 0 0 10 10 December 8 August 8 6 n=45 6 n=31 4 4 2 2 0 0 5 5 2008 4 September 4 March 3 3 n=3 n=0 2 2 1 1 NOT SAMPLED 0 2007 0 5 March 5 April 4 4 n=0 n=0 3 3 2 2

1 NOT SAMPLED1 NOT SAMPLED 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 49 Length‐frequency histograms, separated by upstream and downstream migration, of Nightfish in McAtee Brook. 75

800 Denny Road 700

600 Downstream movement 500 Upstream movement

400

300

200

100

200 Gingalup

150

100

200 Milyeannup Pool 150

100

50 Mean number ofMean fish

0 200 Jalbarragup

150

100

200 Quigup

150

100

6 7 8 9 9 5 05 05 06 6 6 6 0 7 7 7 7 0 7 07 07 8 8 8 8 0 08 08 9 9 0 0 0 0 0 0 0 0 0 0 0 0 l 0 0 0 0 0 t r er er ry h e st er h y e st er r er er h ri e st er er er h y s er be b b a rc n u b rc a n u b be b b rc p n u b b b rc a u b o ru a Ju g a M Ju g o a A Ju g a M g ct em em b M u em M u em ct em em M u em em em M u em O v c e A t A t O v c A t v c /A t o e F ep ep o e ep o e ly ep N D S S N D S N D Ju S

Month

Figure 50 Upstream and downstream movement of Nightfish in the Blackwood River main channel.

Nightfish Downstream Migration 5 Downstream Migration 5 Upstream Migration Upstream Migration 4 4 2005 3 October 3 May 2 n=1 2 n=7 1 1 0 0 5 5 4 November 4 June n=1 n=0 3 3 2 2 1 1 0 0 5 10 4 December 8 August n=2 3 6 n=55 2 4 1 2 0 0 5 2006 5 February September 4 4 n=0 n=0 3 3 2 2 1 1 0 0 5 5 4 March 4 October 3 3 n=3 n=0 2 2 1 1 0 0

Number of Fish Number 5 5 4 June 4 November 3 n=3 3 n=2 2 2 1 1 0 0 5 5 4 August 4 December 3 3 n=5 n= 1 2 2 1 1 0 0 5 5 2008 4 September 4 March 3 n=2 3 n=3 2 2 1 1 0 0 2007 5 March 5 April 4 4 n=1 n=4 3 3 2 2 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Total Length(mm) Total Length(mm)

Figure 51 Length‐frequency histograms, differentiated by upstream and downstream movement, of Nightfish in the Blackwood River main channel.

Table 6 Correlations between upstream and downstream movement of Nightfish in the tributaries of the Blackwood River and prevailing environmental variables during the major migration periods. N.B. Data were log10 transformed, * denotes correlation is significant at the 0.05 level ** at 0.01 level (2‐tailed).

Log Log Log Downstream Log NTU temperature conductivity Log pH Log O2 discharge movement

Log conductivity Pearson Correlation .560

Sig. (2‐tailed) .149

Log pH Pearson Correlation .127 ‐.311

Sig. (2‐tailed) .764 .453

Log O2 Pearson Correlation .022 .301 ‐.580

Sig. (2‐tailed) .958 .469 .132

Log discharge Pearson Correlation .140 .731 .022 ‐.174

Sig. (2‐tailed) .765 .062 .963 .709

Log NTU Pearson Correlation .292 .951(*) ‐.311 ‐.033 .999(*)

Sig. (2‐tailed) .708 .049 .689 .967 .023

Downstream Pearson Correlation ‐.660 ‐.608 .161 .182 ‐.589 ‐.388 movement

Sig. (2‐tailed) .075 .110 .703 .667 .164 .612

Upstream movement Pearson Correlation .191 .225 .678 ‐.228 .430 .264 ‐.187

Sig. (2‐tailed) .650 .591 .064 .588 .335 .736 .657

* Correlation is significant at the 0.05 level (2‐tailed).

** Correlation is significant at the 0.01 level (2‐tailed)

Milyeannup Brook baseflow fish habitat associations

Permanent flow in Milyeannup Brook was found to decrease from a distance of ~2500m from the Blackwood River in March 2006 (i.e. between Mil 6 and Mil 7) to between 1600m‐1800 in 2007 and 2008. Site Mil 6 contained segmented, shallow pool habitats in March 2007 and 2008 and those sites upstream of that site were dry on both occasions (Table 7). Based on discharge estimates at Mil 3 in March 2007 and 2008, baseflow discharge was greater in 2007 (3.6 l/sec) compared to 2008 (2.0 l/sec). Negligible flow was observed at Mil 5 in both March 2007 and 2008 however; clearly deeper pool habitats existed in the former year presumably as a result of higher groundwater level that increased level of baseflow discharge downstream at Mil 3 (Table 7, Figure 52).

Densities of fishes in the habitats at the various sites are presented in Table 8. Balston's Pygmy Perch were consistently recorded at sites Mil 3 (2007, 2008) and Mil 4 (in 2007: not sampled in 2006, 2008). This species was not recorded at Mil 5 suggesting its upstream distribution (despite inter‐annual variations in discharge) to be consistently between Mil 4 and Mil 5 (i.e. <1600m from the Blackwood River). However, as with other species it appears that it may have a preference for deeper pool habitats as suggested by the fact that the species was only recorded in pools and an (albeit relatively weak at this stage i.e., r2 = 0.35) positive relationship existed between habitat depth and density of the species in Mil 3 and Mil 4 (Figures 53‐55). Balston’s Pygmy Perch were found in pool habitats with an average depth of >~19cm.

Other native fishes were consistently recorded as far upstream as Mil 5; further than the Balston’s Pygmy Perch (Figure 53‐55). Although the Western Minnow, Western Pygmy Perch and Nightfish were generally more prevalent and concentrated in pool habitats, each was recorded in riffle zones on at least one occasion during the sampling in the three sites in March 2007 and 2008. This suggests that these species may occupy a wider range of aquatic habitats in Milyeannup Brook during baseflow conditions than Balston’s Pygmy Perch.

Freshwater crayfishes were shown to occupy both pool and riffle habitats with no clear preference being evident (Figures 53‐55). The Gilgie, Restricted Gilgie and Koonac are known to occupy a wide range of permanent and temporary aquatic systems in the south‐west region (Austin and Knott, 1996) and therefore the occupation of both riffle and pool habitats within Milyeannup Brook is not unexpected. Furthermore, their ability to tolerate drought by burrowing into the watertable also allows them to permanently inhabit the upstream, seasonally inundated, sections of Milyeannup Brook (and other tributaries of the Blackwood River).

Milyeannup Brook summary

• Inter‐annual variation in baseflow in Milyeannup Brook is considerable as evidenced by a length of flow decrease from a distance of ~2500m from the Blackwood River in March 2006 down to between 1600‐ 1800m in 2007 and 2008. • The upstream extent of the baseflow distribution of Balston’s Pygmy Perch in Milyeannup Brook is upstream distribution was consistently between Mil 4 and Mil 5 (i.e. <~1600m from the Blackwood River). • Balston’s Pygmy Perch was not recorded in riffle zones on any occasion and were only found in habitats with an average depth of >~19cm suggesting that it may have a preference for pool habitats. • Western Minnow, Western Pygmy Perch and Nightfish were generally more prevalent and concentrated in pool habitats; however, each species was recorded in riffle zones suggesting they may have the ability to occupy a wider range of aquatic habitats in Milyeannup Brook during baseflow conditions than Balston’s Pygmy Perch. • Freshwater crayfishes were shown to occupy both pool and riffle habitats with no clear preference being evident.

Mil 3

Riffle 1 Pool 1 2007 D=3.6 l/sec Maximum depths 2008 0.4 0.4 D=2.0 l/sec

0.3 0.3

0.2 0.2

0.1 0.1

0.0 0.0

g t 3 t 1 2 t 3 ct 1 c on c c e L Long -s x x-sect 2x-se x-se x-sect x-se Mean depths Depth (m) 0.4 0.4

0.3 0.3

0.2 0.2

0.1 0.1

0.0 0.0

g t 1 t 2 ng t 1 t 2 n c c o c L ec Lo -s x-se x-se x-sect 3 x x-se x-sect 3 Section type Mil 5 Pool 1 Pool 2 2007 Maximum depths 2008 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0

1 2 3 2 g t 3 ct ct Long Lon se se -sec x- x-sect x-sect x-sect 1x- x Mean depths Depth (m) Depth 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0

3 g t 1 t 2 t 1 c on ct sec sec L se Long x- x- x-se x- x-sect 2x-sect 3 Section type

Figure 52 Maximum and mean depths of the cross (x‐sect) and longitudinal (long) sections of dominant habitat types (either pool or riffle zones) at Mil 3 and 5. N.B. the greater depths in the pools in Mil 5 in the 2007 during greater discharge (measured at Mil 3) compared with 2008. Note also the lack of clear depth difference between those times in Mil 3 despite the increased discharge measured at that site.

Balston's Pygmy Perch Western Minnow Western Pygmy Perch Nightfish Marron March 2007 Gilgie 0.35 Koonac Restricted Gilgie

0.30

0.25

) -2 0.20

0.15 Density (m 0.10

0.05

0.00

Riffle 1 Pool 1 Pool 2 Habitat type

March 2008 0.35

0.30

0.25

) -2 0.20

0.15 Density (m 0.10

0.05

0.00

Riffle 1 Pool 1 Pool 2 Habitat type

Figure 53 Densities of fish and freshwater crayfish in the three habitat types at Mil 3 during baseflow in 2007 and 2008. N.B. the lower diversity of fish in the riffle habitat compared with the pool habitats.

Balston's Pygmy Perch Western Minnow Western Pygmy Perch Nightfish Marron Gilgie 0.5 Koonac Restricted Gilgie

0.4

)

-2 0.3

0.2 Density (m

0.1

0.0

Riffle 1 Pool 1 Pool 2

Habitat type

Figure 54 Densities of fish and freshwater crayfish in the three habitat types at Mil 4 during baseflow in 2007. N.B. the relatively high abundance of the Balston’s Pygmy Perch in Pool 2.

Balston's Pygmy Perch Western Minnow Western Pygmy Perch Nightfish Marron March 2007 Gilgie 0.7 Koonac Restricted Gilgie

0.6

0.5

) -2 0.4

0.3 Density (m 0.2

0.1

0.0

Pool 1 Pool 2 Habitat type

March 2008 0.5

0.4

)

-2 0.3

0.2 Density (m

0.1

0.0

Pool 1 Pool 2

Habitat type

Figure 55 Densities of fish and freshwater crayfish in the three habitat types at Mil 5 during baseflow in 2007 and 2008. N.B. the lack of Riffle habitat in this section and it approximated the upstream point of permanent aquatic habitat with negligible flow being recorded in both years.

Balston's Pygmy Perch

0.5 r ² = 0.35 0.4 0.3 0.2 0.1 0.0 0.0 0.1 0.2 0.3 0.4 0.5

Western Minnow 0.75 r ² = 0.12

0.50

0.25 ) -2 0.00 0.0 0.1 0.2 0.3 0.4 0.5

Western Pygmy Perch 0.15 r ² = 0.37 Mean density Mean of fish (m 0.10

0.05

0.00 0.0 0.1 0.2 0.3 0.4 0.5

Nightfish 0.15 r ² = 0.20

0.10

0.05

0.00 0.0 0.1 0.2 0.3 0.4 0.5 Mean depth of habitat (m)

Figure 56 Preliminary relationships between the mean depths of habitats sampled within Mil 3, 4 and 5 and the mean density of fish within each of those habitats. N.B. the weak positive relationship between the depth and fish density of Balston’s Pygmy Perch and Western Pygmy Perch.

Table 7 Depths of pool and riffle habitats at sites sampled during baseflow period (March) in 2007 and 2008 in Milyeannup Brook. N.B. Included is the mean temperature, conductivity, pH and dissolved oxygen at each site. Note the reduced flow velocity and discharge during 2008 relative to 2007 and the greater depths at pools at Mil 5 in 2007 relative to 2008 whereas no clear differences existed at Mil 3 between those years. *disconnected pool habitats at Mil 6 in March 2007 and 2008.

2007 2008

Habitat Section Site Temp Cond pH DO Av vel Temp Cond pH DO Turb type taken Max Av Av vel (m/sec) (oC) (µS/cm) (ppm) Max Av (m/sec) and (oC) (µS/cm) (ppm) (NTU) depth depth and disch (l/sec) depth depth disch (m) (m) (m) (m) (l/sec)

Mil 3 Riffle 1 x sect 1 0.2 0.07 0.11 0.07

x sect 2 0.11 0.07 0.08 0.06

x sect 3 0.13 0.07 0.12 0.08

Longitudinal 0.14 0.09 0.15 0.11 16.5 483 5.69 5.30 15.1 481 5.26 5.36 1.52 V = 0.06 V = 0.04 (0) (11.1) (0.01) (0.06) (0.11) (0.71) (0.01) (0.01) (0.13) Pool 2 x sect 1 0.18 0.10 0.28 0.16 D = 3.6 D = 2.0

x sect 2 0.30 0.16 0.25 0.14

x sect 3 0.35 0.25 0.37 0.27

Longitudinal 0.38 0.30 0.36 0.29

Mil 4 Pool 1 x sect 1 0.45 0.28 15.4 514 5.37 4.44 (0.04) (7.79) (0.04) (0.02) x sect 2 0.45 0.29

x sect 3 0.35 0.24

Longitudinal 0.48 0.41

Pool 2 x sect 1 0.5 0.28

x sect 2 0.75 0.53

x sect 3 0.32 0.21

Longitudinal 0.89 0.57

Mil 5 Pool 1 x sect 1 0.55 0.28 0.19 0.11

x sect 2 0.45 0.28 0.44 0.21

x sect 3 0.46 0.26 0.35 0.23

Longitudinal 0.42 0.29 0.43 0.22 V = ~0 V = ~0 17.6 556 5.38 2.68 15.1 591 4.98 4.45 1.51 0.31 0.17 0.25 0.15 Pool 2 x sect 1 (0.19) (10.82) (0.05) (0.04) (0.14) (4.30) (0.03) (0.11) (0.24) D = ~0 D = ~0 x sect 2 0.61 0.38 0.3 0.14

x sect 3 0.85 0.29 0.29 0.168

Longitudinal 0.47 0.36 0.35 0.23

Mil 6 Pool 1* Length (m) 6 4

Width (m) 1 1.2

Max depth 0.08 (m) 0.06

Pool 2* Length (m) 4 1

Width (m) 0.8 1.2

Max depth 0.1 (m) 0.05

Pool 3* Length (m) 5 4

Width (m) 1 1

Max depth 0.1 (m) 0.08

Mil DRY DRY 7A

Mil DRY DRY 7B

Mil 7 DRY DRY

Mil 8 DRY DRY

Mil 9 DRY DRY

Mil DRY DRY 10

Mil DRY DRY 11

Season Total Mean Species Density m2 (total number captured 2006, S.E. 2007, 2008) in Milyeannup Brook using Seine and/or area Electrofishing. Site sampled Lat Long (m2) Native Fishes Feral Fishes Freshwater Crayfishes

Nannatherina Galaxias Edelia Bostockia Galaxiella Oncorhynchus Cherax cainii Cherax Cherax Cherax balstoni occidentalis vittata porosa munda mykiss quinquecarinatus preissii crassimanus

Mil 3 34.0988 115.5699 2

Autumn NS 2006

0.12 0.14 0.24 Autumn 51 0.01 0.06 0.25 0.06

2007 (0.01) (0.04) (0.08) (0.08) (0.08) (0.09) (0.07)

0.17 0.23 Autumn 65 0.01 0.03 0.04 0.04

2008 (0.02) (0.03) (0.05) (0.02) (0.11) (0.04)

Mil 4 34.1012 115.5700

Summer 20 1.25 0.20 0.10 0.10 0.70 0.15 2006 (20) (4) (2) (2) (14) (3)

Winter 125 0.07 0.40 0.10 0.064 0.024 0.06 0.01 2006 (9) (50) (13) (8) (3) (7) (1)

0.17 0.14 0.16 Autumn 64 0.09 0.11 0.03 0.09

2007 (0.04) (0.04) (0.03) (0.04) (0.14) (0.13) (0.05) 89

Autumn

2008

Mil 5 34.1040 115.5708

3 5

Summer 30 0.83 0.03 0.03 0.03 0.30 2006 0.03 (1) (25) (1) (1) (1) (9)

0.39 0.02 Autumn 44.5 0.09 0.22 0.04

2007 (0.06) (0.12) (0.06) (0.27) (0.03)

Autumn 37.5

2008

Mil 6 34.1068 115.5699

2 6

Summer 20 0.600 0.300 0.100 2006 (12) (6) (2)

Autumn Disconected pools 14

2007

Autumn Disconected pools 10 2008

Table 9 Mean densities of fish and freshwater crayfish during baseflow sampling in sites in Milyeannup Brook in 2006, 2007, 2008.

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