Freshwater Ecology Section Arthur Rylah Institute for Environmental Research

Transcription

1 AN ASSESSMENT OF THE AQUATIC FAUNA IN GARDINERS, SCOTCHMANS, BACK AND DAMPER CREEKS for Melbourne Water Waterways and Drainage by Wayne Koster Freshwater Ecology Section Arthur Rylah Institute for Environmental Research May 2002

2 Department of Natural Resources and Environment Title AN ASSESSMENT OF THE AQUATIC FAUNA IN GARDINERS, SCOTCHMANS, BACK AND DAMPER CREEKS Produced by Wayne Koster Arthur Rylah Institute for Environmental Research Department of Natural Resources and Environment PO Box 137 Heidelberg Victoria 3084 Telephone: (03) Facsimile: (03) Produced for Contact Melbourne Water Corporation Waterways and Drainage Rhys Coleman Waterways and Drainage Melbourne Water Corporation GPO Box 4342 Melbourne Victoria 3001 Telephone: (03) Facsimile: (03) Date May 2002 Publication Details Koster, W. M. (2002). An assessment of the aquatic fauna in Gardiners, Scotchmans, Back and Damper creeks. Report to Melbourne Water. Freshwater Ecology Section, Department of Natural Resources and Environment, Melbourne. Cover photographs (top to bottom):! Damper Creek at Park Road! Scotchmans Creek at Regent Street! Gardiners Creek at Warrigal Road! Back Creek at Dawson Drive! Gardiners Creek at Glenferrie Road (All photos: W. Koster) Department of Natural Resources and Environment Freshwater Ecology

3 Summary Background To determine the health of streams in the Melbourne area and to identify priority management areas, Melbourne Water Corporation has established the Tributary Investigation Program combining a range of stream health indicators that are assessed at a variety of temporal and spatial scales. The Freshwater Ecology Section of the Department of Natural Resources and Environment was commissioned to undertake the aquatic fauna component of the Tributary Investigation Program in the Gardiners Creek catchment. The objective of this investigation was to provide an assessment of the current state of the aquatic fauna in the catchment and to identify the primary factors impacting on the condition of these communities. Fish Surveys A total of ten survey sites were selected within the study region, in consultation with Melbourne Water. Five sites were selected on Gardiners Creek, three sites on Scotchmans Creek, and one site on each of Back and Damper creeks. Aquatic fauna surveys were conducted between the 25 th of January and 1 st of February 2002 using a portable backpack electrofishing unit. At each survey site a standard, two-pass electrofishing technique was used. Species Distribution and Abundance A total of 416 individual fish representing seven families and nine species (four native and five exotic) were collected during the aquatic fauna surveys. Two species of decapod crustacea were also recorded. At each site, the diversity of native species was low and represented less than 30% of the species expected to occur under natural conditions. Three of the four native species collected during these surveys were migratory species and require free passage between marine and freshwater environments at both adult and larval/juvenile stages of their life cycle. The diversity and abundance of native species tended to be higher in the lower reaches of the catchment than in the upper reaches. The diversity and abundance of exotic species varied throughout the study area. In general, native species dominated fish communities in Scotchmans Creek and the lower reaches of Gardiners Creek, whilst in Back Creek and the middle to upper reaches of Gardiners Creek, exotic species dominated fish communities. Department of Natural Resources and Environment Freshwater Ecology i

4 The native common galaxias (Galaxias maculatus) were the most abundant species within the study region. Short-finned eel (Anguilla australis) and eastern gambusia (Gambusia holbrooki) were also relatively common. Broad-finned galaxias (Galaxias brevipinnis), flat-headed gudgeon (Philypnodon grandiceps), and the exotic yellow-fin goby (Acanthogobius flavimanus), goldfish (Carassius auratus), carp (Cyprinus carpio) and oriental weatherloach (Misgurnus anguillicaudatus) were all recorded in low numbers. Condition of Aquatic Fauna Assemblages The rationale employed in this study to assess the condition of aquatic fauna assemblages uses a biotic index incorporating two parameters of aquatic fauna population dynamics; naturalness (species diversity) and exotic abundance. The condition of aquatic fauna assemblages varied throughout the study area, although the majority of sites were described as having degraded to moderate health. It appears that under certain circumstances the rationale used to assess the condition of aquatic fauna assemblages provides false assessment as it affords undue importance to the absence of exotic species when population naturalness is low. This result has been found in previous studies and requires modification if it is to be used in future. Impacts on Environmental Condition This study has identified numerous factors impacting on environmental condition within the study area and more specifically on aquatic fauna assemblages. These include: " Barriers to fish migration, " Introduction of exotic species, " Changes to stream channels, " Changes to water quality, " Clearing of riparian vegetation. Department of Natural Resources and Environment Freshwater Ecology ii

5 TABLE OF CONTENTS SUMMARY... i 1. INTRODUCTION MATERIALS AND METHODS STUDY AREA STUDY SITES SAMPLING METHODOLOGY Aquatic Fauna Survey Quantification of Site Attributes Analyses RESULTS HISTORICAL DATA GENERAL SURVEY RESULTS General Site Characteristics Site Specific Descriptions Fish Survey Results DISCUSSION SPECIES DIVERSITY, DISTRIBUTION AND ABUNDANCE HEALTH OF AQUATIC FAUNA ASSEMBLAGES IMPACTS ON AQUATIC FAUNA SIGNIFICANT SPECIES RECOMMENDATIONS ACKNOWLEDGMENTS REFERENCES APPENDIX A GARDINERS CREEK GC GARDINERS CREEK GC GARDINERS CREEK GC GARDINERS CREEK GC GARDINERS CREEK GC BACK CREEK BC SCOTCHMANS CREEK SC SCOTCHMANS CREEK SC SCOTCHMANS CREEK SC DAMPER CREEK DC Department of Natural Resources and Environment Freshwater Ecology

6 1. INTRODUCTION To determine the health of streams in the Melbourne area, and to identify priority management areas, Melbourne Water Corporation has established a stream health assessment program including ongoing monitoring programs such as the Biological Monitoring Program and the Tributary Investigation Program. These programs combine a range of stream health indicators that are assessed at a variety of temporal and spatial scales. The Freshwater Ecology Section of the Department of Natural Resources and Environment was commissioned to undertake the aquatic fauna (fish and decapod crustacea) component of the Tributary Investigation Program in the Gardiners Creek catchment. The objective of this investigation was to provide an assessment of the current state of the aquatic fauna in the catchment and to identify the primary factors impacting on the condition of these communities. There have been several previous studies examining the environmental health of streams in the Gardiners Creek catchment (Melbourne Water 1997, Hardwick and Waller 1999, Yarra Care 1999, Bessell-Browne 2000, Deveraux et al. 2000). A report by Melbourne Water (1997) on the health of waterways within the Gardiners Creek system described water quality and stream condition as poor and community health of aquatic macroinvertebrates as very poor to fair. Similarly, Bessell-Browne (2000) reported that no sites in Gardiners Creek complied with Waters of Victoria (WoV) Schedule F7 (Government of Victoria 1999) objectives for biological indicators and that some sites failed to comply with various physico-chemical objectives. There have been few previous fish surveys conducted within the study region and therefore information on the distribution and abundance of aquatic fauna in the Gardiners Creek catchment is limited. This document provides a summary of historical fish surveys and a brief assessment of the current status (species diversity and abundance) of the fish assemblages in the Gardiners Creek catchment. Primary issues within the catchment likely to be impacting on the health of aquatic fauna populations are also identified. Department of Natural Resources and Environment Freshwater Ecology 1

7 # # # An Assessment of Aquatic Fauna in Gardiners, Scotchmans, Back and Damper Creeks 2. MATERIALS AND METHODS 2.1 STUDY AREA The Gardiners Creek catchment is located in the south-eastern suburbs of Melbourne in the lower reaches of the Yarra Basin (Figure 2-1). The catchment is urbanised and covers an area of approximately hectares (Poussard 1996). Gardiners Creek under natural conditions comprised a number of shallow channels through a swampy floor, fringed by dense thickets of swamp paperbark (Melaleuca ericifolia) (Duxbury 1990). As urbanisation of Melbourne progressed the creek environment dramatically changed, particularly due to stream channelisation and clearing of vegetation (Duxbury 1990). Gardiners Creek originates near Blackburn at an altitude of approximately 120 m.a.s.l., flowing for approximately 12 kilometres in a south-westerly direction, before travelling a further eight kilometres in a north-westerly direction prior to its confluence with the Yarra River near Hawthorn. A natural rock barrier on the lower reaches of the Yarra River near Queen Street, approximately five kilometres downstream of the Gardiners Creek confluence, historically represented the upstream limit of tidal influence (Piha 1992). During the 1860s the barrier was removed and consequently the tidal influence extended upstream and now the lower reaches of Gardiners Creek are tidally affected. Scotchmans Creek originates near Mount Waverley at an altitude of approximately 80 m.a.s.l., flowing for approximately 10 kilometres in a westerly direction before entering Gardiners Creek near East Malvern. The two other main streams in the catchment are Damper and Back creeks, located in the upper and lower reaches of the catchment respectively. Mean annual rainfall in the catchment is approximately 750 mm (Poussard 1996). River # Hawthorn Victoria # Blackburn # Yarra GC1 $ Gardiners # Glen Iris GC2 $ BC1 $ Waterways # Locality Creek $ Survey site East Malvern # N Kilometers Back Creek Ashburton # GC3 $ SC1 $ Scotchmans Gardiners SC2 $ GC4 $ Ashwood # Creek $ DC1 # C r e ek GC5 $ Blackburn Lake Damper Creek Mount Waverley $ SC3 Figure 2-1. Gardiners Creek catchment including location of aquatic fauna survey sites (Refer to Table 2-1 for site details). Department of Natural Resources and Environment Freshwater Ecology 2

8 2.2 STUDY SITES A total of ten survey sites were selected within the study region, in consultation with Melbourne Water; five sites in Gardiners Creek, three sites in Scotchmans Creek, and one site in each of Back and Damper creeks (Figure 2-1, Table 2-1). At each site, a single survey reach was established to represent the available aquatic habitat attributes including flow types and cover elements. The location of each survey reach was defined by Australian Map Grid Reference (AMG) from topographic 1:25,000 scale maps (Table 2-1). Table 2-1. Location of aquatic fauna survey sites on Gardiners, Scotchmans, Back and Damper creeks. Creek and Site Gardiners GC1 Location Melway Reference AMG Reference* (eastings-northings) Downstream of concrete channel, Glenferrie 59B Road, Hawthorn GC2 Downstream of Tooronga Road, Malvern 59E GC3 Downstream of Warrigal Road, Ashburton 60G GC4 Downstream of Station Street, Burwood 61C GC5 Upstream of Middleborough Road, Blackburn 47K Back BC1 Downstream of Dawson Drive, Glen Iris 59K Scotchmans SC1 Footbridge at Malvern Valley Golf Course, 69D East Malvern SC2 Downstream of Huntingdale Road, 69K Chadstone SC3 Upstream of Regent Street, Mount Waverley 70G Damper DC1 Upstream of Park Road, Mount Waverley 61D * - Map number 7922, zone SAMPLING METHODOLOGY Aquatic Fauna Survey Aquatic fauna surveys were conducted between January 25 th and February 1 st 2002 using a portable backpack Smith-Root model 12 electrofishing unit. At all sites a standard, twopass electrofishing technique, with stop nets (5 mm stretched mesh) positioned at the upstream and downstream margins of the survey reach, was used. This technique is identical with that used in all other stream health assessments conducted by Freshwater Ecology for Melbourne Water (Raadik and O Connor 1997, Raadik and Zampatti 1998, Raadik and Lieschke 1999, Raadik et al., 1999, Lieschke and Raadik 1999, Close 2000, Close et al. 2001). The operator fished upstream from the downstream stop net, fishing all habitats along the edges and in the middle of the channel, stunning and retrieving fish. An assistant followed the operator collecting any animals missed by the operator. Department of Natural Resources and Environment Freshwater Ecology 3

9 All fish recorded were identified and counted. For samples containing many (>30) individuals of a single species, a representative subsample of 20 specimens was measured for length (to the nearest 1 mm - length to caudal fork) and weight (wet weight to the nearest 0.1 g for weights < 100 g and 1 g for weights > 100g). The number and bulk weight for additional individuals of each species was also recorded. Nomenclature for fish species follows Allen (1989), Paxton et al. (1990), McDowall (1997) and Jerry et al. (2001), Riek (1969) and Horwitz (1990) for decapod crustacea, and Williams & Smith (1979) for freshwater shrimps Quantification of Site Attributes Hydrology For each survey reach the average width (m) was calculated from at least five measurements. Average depth (m) within each survey reach was calculated from depth measurements taken across at least five transects strategically positioned to incorporate a representative sample of depths. Spot measurements of water quality parameters were recorded within each survey reach. Water temperature (ºC) and electrical conductivity (µs.cm -1 ) were measured with a WTW LF 320 meter, dissolved oxygen (mg.l -1 ) with a WTW OXI 320 meter, turbidity (NTU) with a HACH 2100P Turbidimeter and ph with a WTW ph 320 meter. A measure of instantaneous discharge was recorded for each survey reach on the day of survey. A cross-channel transect, perpendicular to the flow, was established at specific locations in the vicinity of each survey reach and preferably downstream. Discharge transects were located where channel morphology was uniform in terms of flow, depth, width and slope and in areas with minimal upstream obstacles such as rocks, logs or macrophyte beds. Any upstream obstacles were temporarily removed to increase laminar flow and avoid turbulence, eddies and dead-water zones. Instantaneous discharge was estimated using depth and flow measurements taken across discharge transects according to the methodology outlined in Gordon et al. (1992). Using the equation below, instantaneous discharge was calculated and expressed in megalitres per day (ML.d -1 ). Q = w D v + w D v w D v n n n Where w is width in metres, D is vertical depth in metres and v is the average velocity Habitat Attributes The relative abundance (% of wetted area) of hydraulic flow components, habitat attributes and cover elements was estimated for each survey reach. Hydraulic flow type at each site was defined using the categories; cascade, rapid, riffle, glide, run, pool or backwater (after Department of Natural Resources and Environment Freshwater Ecology 4

10 Anderson & Morrison 1989, Anderson et al. 1989). Streambed geology was described in terms of percentage composition of various particle size groups, namely boulder (particle size > 256 mm), cobble ( mm particle size), pebble (16-63 mm particle size), gravel (2-15 mm particle size), sand (0.1-2 mm particle size) and silt/clay (particle size < 0.1 mm). The relative abundance of dominant cover elements including substratum, woody debris (logs, branches), organic debris (leaves, bark), bank overhang, vegetation overhang and aquatic vegetation was recorded Analyses Catch per unit effort, biomass and density An estimate of catch per unit effort (CPUE) was calculated for each site and expressed in terms of the number of fish recorded per hour. The summed time of two electrofishing passes was used in the calculation of CPUE. Estimates of biomass (g.m -2 ) and density (fish.m -2 ) were also calculated for each site. Stream health The rationale implemented in this study for assessing the condition of aquatic fauna assemblages is consistent with the methods used in previous "Tributary Investigation" surveys. Condition was assessed based on two indicators; the naturalness of fish and the relative abundance of exotic species at each site. The naturalness of aquatic fauna populations was expressed in terms of the proportion (%) of native species recorded at each site of the total number of native species expected to occur at each site under natural conditions. The list of expected taxa for each site was compiled using historical distribution data (DNRE 2002). As only a few fish surveys have been conducted in the study area, the list of expected taxa was further refined using expert knowledge of the distribution and habitat requirements of Victorian fish species. Both indicators of stream health (naturalness and relative abundance of exotic species) were ranked according to the criteria in Table 2-2. The two ranks were then summed to provide an indication of condition (Table 2-2). As little distributional data is available for decapod crustacea in the study area, they were omitted from the assessment. Table 2-2. Category, rank and description of stream assessment indicators; naturalness (A) exotic species abundance (B) and stream health assessment (A+B). Naturalness (A) Exotic abundance (B) Stream health (A+B) Category Rank Description Category Rank Description Rank Description % 9 Excellent 0 % 9 Excellent >14 Excellent % 7 Good 1-9 % 7 Good Good % 3 Moderate % 5 Moderate 7-9 Moderate 1 30 % 1 Poor % 3 Poor 4-6 Poor 0 % 0 Degraded % 0 Degraded 0-3 Degraded Department of Natural Resources and Environment Freshwater Ecology 5

11 3. RESULTS 3.1 HISTORICAL DATA Thirteen species of freshwater fish have been reported from the Gardiners Creek catchment (DNRE 2002, Museum of Victoria - MV) (Table 3-1). Six of these species are native, including at least one species that migrates between freshwater and marine habitats at some stage in its life cycle, namely short-finned eel (Anguilla australis) (Table 3-1). An unidentified galaxias species reported from Blackburn Lake is likely to represent an additional native migratory species. One species of decapod crustacea has also been reported (Table 3-1). One of the native species, namely dwarf galaxias (Galaxiella pusilla), is classified as lower-risk - near threatened in Victoria (DNRE 2000) and vulnerable nationally (ANZECC 2000), and protected through their listing on the Flora and Fauna Guarantee Act 1988 and the Environment Protection and Biodiversity Conservation Act Table 3-1. Native and exotic freshwater fish species previously recorded from the Gardiners Creek catchment. Scientific name Common Name Location Native fish species Anguilla australis Short-finned eel Blackburn Lake Galaxias spp. Blackburn Lake Galaxiella pusilla Dwarf galaxias Scotchmans Creek, Oakleigh Gadopsis marmoratus River blackfish Gardiners Creek, Malvern East Nannoperca australis Southern pygmy perch Scotchmans Creek, Oakleigh Retropinna semoni Australian smelt Blackburn Lake Exotic fish species Gambusia holbrooki Eastern gambusia Blackburn Lake Salmo trutta Brown trout Gardiners Creek, Malvern East Carassius auratus Goldfish Blackburn Lake Misgurnus anguillicaudatus Oriental weatherloach Gardiners Creek, Malvern East Rutilus rutilus Roach Blackburn Lake Cyprinus carpio Carp Blackburn Lake Perca fluviatilis Redfin Blackburn Lake Decapod crustacea Cherax destructor Common yabby Blackburn Lake Few fish surveys have been documented within the study region (DNRE 2002). Most surveys were conducted before 1990 and none have been conducted in Back or Damper creeks (DNRE 2002). River blackfish (Gadopsis marmoratus) and brown trout (Salmo trutta) were recorded in Gardiners Creek near High Street, Malvern East, ca (DNRE 2002). Roach (Rutilus rutilus), redfin (Perca fluviatilis) and goldfish (Carassius auratus) were recorded in Blackburn Lake in 1973, ca. 1987, and 1988 (DNRE 2002). Dwarf galaxias and southern pygmy perch (Nannoperca australis) were recorded in Department of Natural Resources and Environment Freshwater Ecology 6

12 Scotchmans Creek, Oakleigh, pre-1985 (MV). This record of dwarf galaxias represents the only documented record of the species in the Yarra River basin (DNRE 2002). Short-finned eel, galaxias spp., eastern gambusia (Gambusia holbrooki) and carp (Cyprinus carpio) were recorded in Blackburn Lake, ca (DNRE 2002). Oriental weatherloach (Misgurnus anguillicaudatus) were recorded in Gardiners Creek near Burke Road, Glen Iris, 1991 (DNRE 2002). Australian smelt (Retropinna semoni) and common yabby (Cherax destructor) were recorded in Blackburn Lake in 1993 (Deveraux et al. 2000). 3.2 GENERAL SURVEY RESULTS General Site Characteristics Gardiners Creek The five survey sites located on Gardiners Creek were positioned reasonably evenly throughout the catchment in terms of altitude and distance to river mouth (Table 3-2). Reach characteristics varied between sites (Table 3-2). Average stream width generally decreased with distance upstream, ranging from 11.3 m at the most downstream site (GC1) to 3.5 m at the most upstream site (GC5). Average stream depth was less than 0.5 m at all sites, except at the second most upstream site (GC4) where the average stream depth was 1.0 m. Physico-chemical water quality parameters are shown in Table 3-2. Water temperature ranged from 19.0ºC at the second most downstream site (GC2) to 34.2ºC at the mid-reach site (GC3). Electrical conductivity concentrations were highest (273.0 µs.cm -1 ) at the most downstream site (GC1) and lowest (50.1 µs.cm -1 ) at the most upstream site (GC5). Dissolved oxygen concentrations were highest (9.7 mg.l -1 ) at the mid-reach site (GC3) and lowest (4.6 mg.l -1 ) at the most downstream site (GC1). Turbidity ranged from 4.4 NTU at the mid-reach site (GC3) to 17.7 NTU at the second most upstream site (GC4). At most sites ph was close to neutral (6.8 to 7.1), except at the mid-reach site where the level was 9.9. At the time of survey, stream discharge ranged from 2.1 ML.d -1 (GC5) to 5.4 ML.d -1 (GC3). The streambed at all sites comprised varying amounts of both fine (e.g. sand) and coarse substratum (e.g. gravel, boulder) (Table 3-2). At all sites sand and gravel comprised at least 50% of the substrate. Silt and clay were only present in small quantities in the upper catchment (sites GC4, GC5). Coarse substrata (e.g. pebbles, cobble, boulder) tended to become more abundant with increasing distance downstream from source. The occurrence of coarse substrata in the mid to lower reaches of the catchment appears to be associated with stream restoration works, specifically stabilisation of the streambed and banks. Instream cover at all sites comprised predominantly rock (20-40%), except at the second most upstream site (GC4) where aquatic vegetation was dominant (30%) (Table 3-2). The Department of Natural Resources and Environment Freshwater Ecology 7

13 hydrology at all sites was dominated by pool habitat (80-100%), except at the mid-reach site (GC3) where riffle was the dominant flow type (70%) (Table 3-2). Table 3-2. Stream habitat survey information and habitat structure at each of the study sites located in Gardiners Creek. Substrata and instream cover are defined in the text. Habitat Survey Characteristics GC1 GC2 GC3 GC4 GC5 Stream characteristics Elevation (m.a.s.l.) Distance to river mouth (km)* Discharge (ML.d -1 ) Reach characteristics Mean stream width (m) Mean depth (m) Water quality Temperature (ºC) Electrical conductivity (µs.cm -1 ) Dissolved oxygen (mg.l -1 ) Turbidity (NTU) ph Substrate composition (%) Sheet rock Boulder Cobble Pebble Gravel Sand Silt Clay Instream cover (% wetted area) Substrate (Rock) Logs/Log jams Branches/Branch piles Leaves, organic debris Bank overhang Vegetation overhang Urban rubbish Aquatic vegetation Flow type (%) Rapid/cascade Run Riffle Glide Pool Backwater * - Confluence of Gardiners Creek and Yarra River. Department of Natural Resources and Environment Freshwater Ecology 8

14 Back Creek The one survey site on Back Creek was located in the lower reaches of the catchment, approximately 300 m upstream from its confluence with Gardiners Creek. Physico-chemical water quality parameters are shown in Table 3-3. At the time of survey, stream discharge was zero ML.d -1. The streambed at Back Creek was dominated by fine substrata including sand and clay (Table 3-3). Instream habitat was scarce although small amounts of coarse substratum (rock), overhanging vegetation and bank and aquatic vegetation were present (Table 3-3). Flow type comprised predominantly pool habitat (Table 3-3). Scotchmans Creek The three survey sites located on Scotchmans Creek were positioned reasonably evenly throughout the catchment in terms of altitude and distance to river mouth (Table 3-3). Reach characteristics were similar at each site although the mid-reach site (SC2) was slightly narrower than the other two sites (Table 3-3). Physico-chemical water quality parameters are shown in Table 3-3. Water temperature and electrical conductivity concentrations decreased with increasing distance upstream. Water temperature ranged from 20.5ºC at the most downstream site (SC1) to 18.7ºC at the most upstream site (SC3). Electrical conductivity concentrations ranged from µs.cm -1 at the most downstream site (SC1) to µs.cm -1 at the most upstream site (SC3). Dissolved oxygen concentrations were highest (7.9 mg.l -1 ) at the most downstream site (SC1) and lowest (2.9 mg.l -1 ) at the mid-reach site (SC2). Turbidity ranged from 3.1 NTU at the mid-reach site (SC2) to 8.4 NTU at the most upstream site (SC3). The level of ph (6.9 to 7.2) was close to neutral at all sites. At the time of survey, stream discharge ranged from 0.7 ML.d -1 (SC3) to 1.0 ML.d -1 (SC2). The streambed at all sites comprised varying amounts of both fine (e.g. sand) and coarse substratum (e.g. gravel, boulder) (Table 3-3). At all sites sand and gravel comprised at least 40% of the substratum. Silt was only present in small quantities in the upper catchment (site SC3). Instream cover was scarce at the most upstream (SC3) and downstream (SC1) sites, while at the mid-reach site (SC2) aquatic vegetation was abundant (60%) (Table 3-3). The hydrology at all sites was dominated by pool habitat (70-80%) (Table 3-3). Damper Creek The one survey site on Damper Creek was located in the upper reaches of the catchment. Physico-chemical water quality parameters are shown in Table 3-3. At the time of survey, stream discharge was zero ML.d -1. The streambed at Damper Creek comprised approximately equal proportions of fine (e.g. sand, silt) and coarse (boulder, cobble) substrata (Table 3-3). Instream habitat was abundant and comprised aquatic vegetation, rock and vegetation overhang (Table 3-3). Flow type comprised predominantly pool habitat (Table 3-3). Department of Natural Resources and Environment Freshwater Ecology 9

15 Table 3-3. Stream habitat survey information and habitat structure at each of the study sites located in Scotchmans, Back and Damper creeks. Substrata and instream cover are defined in the text. Habitat Survey Characteristics Site BC1 Site SC1 Site SC2 Site SC3 Site DC1 Stream characteristics Elevation (m.a.s.l.) Distance to river mouth (km)* Discharge (ML.d -1 ) Reach characteristics Mean stream width (m) Mean depth (m) Water quality Temperature (ºC) Electrical conductivity (µs.cm -1 ) Dissolved oxygen (mg.l -1 ) Turbidity (NTU) ph Substrate composition (%) Sheet rock Boulder Cobble Pebble Gravel Sand Silt Clay Instream cover (% wetted area) Substrate (Rock) Logs/Log jams Branches/Branch piles Leaves, organic debris Bank overhang Vegetation overhang Urban rubbish Aquatic vegetation Flow type (%) Rapid/cascade Run Riffle Glide Pool Backwater * - Confluence of Gardiners Creek and Yarra River. Department of Natural Resources and Environment Freshwater Ecology 10

16 3.2.2 Site Specific Descriptions Gardiners Creek downstream of Glenferrie Road, Hawthorn This reach was located downstream of Glenferrie Road, below a concrete channelised stream section, and extended from the base of a concrete weir wall to 100 m downstream (Figure 3-1). The site was dominated by pool habitat (98%) and the reach was tidally influenced. Average stream width and depth were 11.3 m and 0.4 m respectively. The riparian vegetation comprised mostly exotic grasses (50%) and some native trees (10%) and exotic shrubs (5%). A large proportion of the riparian zone comprised bare ground (45%). The streambed comprised predominantly pebble (30%), gravel (30%) and sand (20%). Instream habitat available as cover to aquatic fauna comprised coarse substratum (20%) and aquatic vegetation (1%). Streamside disturbances included a cleared riparian zone, a bridge, urban rubbish, a concrete weir and channel, and exotic vegetation. Figure 3-1. Gardiners Creek downstream of Glenferrie Road, Hawthorn. Department of Natural Resources and Environment Freshwater Ecology 11

17 Gardiners Creek downstream of Tooronga Road, Malvern This reach extended from immediately below the bridge on Tooronga Road to 100 m downstream (Figure 3-2). Hydraulic habitats included pool (80%), riffle (15%) and run (5%). Average stream width and depth were 5.3 m and 0.3 m respectively. The riparian vegetation comprised mostly native trees (60%) and exotic grasses (20%). The streambed comprised predominantly gravel and sand (50% combined), and boulder and cobble (40% combined). Instream habitat available as cover to aquatic fauna comprised coarse substratum (40%), aquatic vegetation (5%) and organic debris (2%). Streamside disturbances included a bridge, a drain, urban rubbish and exotic vegetation. Figure 3-2. Gardiners Creek downstream of Tooronga Road, Malvern. Department of Natural Resources and Environment Freshwater Ecology 12

18 Gardiners Creek downstream of Warrigal Road, Ashburton This reach extended from approximately 10 m to 110 m downstream of the bridge on Warrigal Road (Figure 3-3). Hydraulic habitat included riffle (70%), glide (25%) and run (5%). Average stream width and depth were 4.8 m and 0.2 m respectively. The riparian vegetation comprised mostly exotic grasses (60%) and native trees and shrubs (30% combined). The streambed comprised predominantly gravel and sand (60% combined) and boulder (25%). Instream habitat available as cover to aquatic fauna comprised coarse substratum (40%), organic debris (5%) and aquatic vegetation (1%). Streamside disturbances included a bridge, cleared riparian zone, a drain, urban rubbish, exotic vegetation and concrete channel. Figure 3-3. Gardiners Creek downstream of Warrigal Road, Ashburton. Department of Natural Resources and Environment Freshwater Ecology 13

19 Gardiners Creek downstream of Station Street, Burwood This reach extended from immediately below the bridge on Station Street to 100 m downstream (Figure 3-4). The hydrology was dominated by pool habitat (100%). Average stream width and depth were 5.8 m and 1.0 m respectively. The riparian vegetation comprised mostly exotic grasses (90%). The streambed comprised predominantly sand (60%) and boulder (20%). Instream habitat available as cover to aquatic fauna comprised aquatic vegetation (30%), rock (20%) and organic debris (10%). Streamside disturbances included a bridge, a drain, cleared riparian zone, urban rubbish and exotic vegetation. Figure 3-4. Gardiners Creek downstream of Station Street, Burwood. Department of Natural Resources and Environment Freshwater Ecology 14

20 Gardiners Creek upstream of Middleborough Road, Blackburn This reach extended from the culvert at Middleborough Road to 100 m upstream (Figure 3-5). Hydraulic habitats included pool (80%), run (10%), riffle (5%) and glide (5%). Average stream width and depth were 3.5 m and 0.4 m respectively. The riparian vegetation comprised mostly exotic grasses (50%) and native trees (30%). The streambed comprised predominantly sand (40%), gravel (30%) and sheetrock (20%). Instream habitat available as cover to aquatic fauna comprised coarse substratum (20%), branches (5%), organic debris (5%), vegetation overhang (5%) and aquatic vegetation (5%). Streamside disturbances included bank erosion, a cleared riparian zone, a culvert and exotic vegetation. Figure 3-5. Gardiners Creek upstream of Middleborough Road, Blackburn. Department of Natural Resources and Environment Freshwater Ecology 15

21 Back Creek downstream of Dawson Drive, Glen Iris This reach extended from the culvert on Dawson Drive to 100 m downstream (Figure 3-6). The hydrology was dominated by pool habitat (98%). Average stream width and depth were 4.9 m and 0.5 m respectively. The riparian vegetation comprised mostly willows (50%) and exotic creepers and grasses (45% combined). The streambed comprised predominantly sand (40%) and clay (30%). Instream habitat available as cover to aquatic fauna comprised coarse substratum (10%), bank overhang (5%), vegetation overhang (1%) and aquatic vegetation (1%). Streamside disturbances included a cleared riparian zone, a culvert, urban rubbish, a drain and exotic vegetation. Figure 3-6. Back Creek downstream of Dawson Drive, Glen Iris. Department of Natural Resources and Environment Freshwater Ecology 16

22 Scotchmans Creek at Malvern Valley Golf Course, East Malvern This reach was located on the Malvern Valley Golf Course and extended 100 m upstream of the footbridge (Figure 3-7). Hydraulic habitats included pool (80%), riffle (15%) and run (5%). Average stream width and depth were 2.9 m and 0.3 m respectively. The riparian vegetation comprised mostly exotic grasses (60%) and exotic trees (20%). The streambed comprised predominantly clay (35%), gravel (20%) and sand (20%). Instream habitat available as cover to aquatic fauna comprised aquatic vegetation (10%), coarse substratum (10%) and urban rubbish (5%). Streamside disturbances included bank erosion, a cleared riparian zone, a bridge, exotic vegetation and concrete channel. Figure 3-7. Scotchmans Creek at Malvern Valley Golf Course, East Malvern. Department of Natural Resources and Environment Freshwater Ecology 17

23 Scotchmans Creek downstream of Huntingdale Road, Chadstone This reach extended from approximately 25 m to 125 m downstream of the culvert at Huntingdale Road (Figure 3-8). Hydraulic habitats included pool (80%), run (10%) and glide (10%). Average stream width and depth were 1.7 m and 0.3 m respectively. The riparian vegetation comprised mostly exotic grasses (80%) and native trees and shrubs (20% combined). The streambed comprised predominantly gravel (30%), sand (30%) and cobble (20%). Instream habitat available as cover to aquatic fauna comprised aquatic vegetation (60%), coarse substratum (5%), vegetation overhang (5%) and organic debris (2%). Streamside disturbances included a cleared riparian zone, urban rubbish, a culvert, exotic vegetation and a drain. Figure 3-8. Scotchmans Creek downstream of Huntingdale Road, Chadstone. Department of Natural Resources and Environment Freshwater Ecology 18

24 Scotchmans Creek upstream of Regent Street, Mount Waverley This reach extended from the culvert at Regent Street to approximately 100 m upstream (Figure 3-9). Hydraulic habitats included pool (70%) and riffle (30%). Average stream width and depth were 3.0 m and 0.3 m respectively. The riparian vegetation comprised mostly exotic grasses (45%), willows (40%) and native trees and shrubs (20% combined). The streambed comprised predominantly pebble and gravel (60% combined). Instream habitat available as cover to aquatic fauna comprised coarse substratum (10%), bank overhang (10%) and aquatic vegetation (5%). Streamside disturbances included a cleared riparian zone, a culvert, exotic vegetation, a section of bluestone channel, and a drain. Figure 3-9. Scotchmans Creek upstream of Regent Street, Mount Waverley. Department of Natural Resources and Environment Freshwater Ecology 19

25 Damper Creek upstream of Park Road, Mount Waverley This reach extended from the culvert on Park Road to approximately 100 m upstream (Figure 3-10). Hydraulic habitats included pool (80%) and riffle (20%). Average stream width and depth were 1.7 m and 0.1 m respectively. The riparian vegetation comprised mostly native shrubs and trees (85% combined). The streambed comprised predominantly cobble (30%), boulder (20%), sand (20%) and silt (20%). Instream habitat available as cover to aquatic fauna comprised aquatic vegetation (70%), rock (10%) and vegetation overhang (5%). Streamside disturbances included a culvert and exotic vegetation. Figure Damper Creek upstream of Park Street, Mount Waverley. Department of Natural Resources and Environment Freshwater Ecology 20

26 3.2.3 Fish Survey Results Species diversity and abundance A total of 416 individual fish representing seven families and nine species were recorded during the aquatic fauna surveys (Table 3-4, 3-5). Four native species were collected, three of which are migratory 1 (Table 3-4). Two species of decapod crustacea were also recorded (Table 3-4). Native fish species contributed 66% of the total fish fauna recorded, and overall, native migratory fish contributed 61% of the total fish fauna recorded, native nonmigratory fish 5% and exotic fish 34% (Table 3-5). In general, the majority of native migratory fish species were recorded in the lower reaches of the study area (Table 3-5). None of the native species are considered threatened in Victoria (DCNR 1995, DNRE 2000). Table 3-4. Aquatic fauna recorded in Gardiners, Scotchmans, Back and Damper creeks. Scientific name Common name Gardiners Back Scotchmans Damper Native fish species Anguilla australis* Short-finned eel Galaxias brevipinnis* Broad-finned galaxias Galaxias maculatus* Common galaxias Philypnodon grandiceps Flat-headed gudgeon Exotic fish species Acanthogobius flavimanus Yellow-fin goby Carassius auratus Goldfish Cyprinus carpio Carp Gambusia holbrooki Eastern gambusia Misgurnus anguillicaudatus Oriental weatherloach Decapod crustacea Cherax destructor Common yabby Paratya australiensis Freshwater shrimp - Species present. * - Migrates between freshwater and marine habitats at some stage in life cycle. The number of fish species recorded at each site varied, ranging from zero species at Damper Creek (DC1) to five species at the mid-reach and most downstream site on Gardiners Creek (GC3 and GC1 respectively) (Table 3-5). The number of individual fish recorded at each site also varied, ranging from zero individuals at Damper Creek (DC1) to 97 individuals at the second most downstream site on Gardiners Creek (GC2) (Table 3-5). In Gardiners Creek, the number of fish species recorded at each site ranged from three species at the most upstream (GC5) and second most downstream (GC2) sites to five species at the mid-reach (GC3) and most downstream (GC1) sites (Table 3-5). The number 1 Require free passage between marine and freshwater environments at both adult and larval/juvenile stages of their life cycle. Department of Natural Resources and Environment Freshwater Ecology 21

27 of individuals recorded at each site ranged from five at the most upstream site (GC5) to 97 at the second most downstream site (GC2) (Table 3-5). Twenty-seven fish representing three species were recorded at Back Creek (BC1) (Table 3-5). In Scotchmans Creek, the number of fish species and individuals recorded at each site increased with increasing distance downstream from source (Table 3-5). Four individuals of one species were collected at the most upstream site (SC3), 15 fish representing three species were recorded at the mid reach site (SC2), while 74 fish representing four species were recorded at the downstream site (SC1) (Table 3-5). In terms of abundance, common galaxias (Galaxias maculatus) were the dominant species with 176 individual fish recorded (Table 3-5). Short-finned eel and the exotic eastern gambusia were also relatively common; 72 and 79 individuals respectively (Table 3-5). Low numbers of broad-finned galaxias (Galaxias brevipinnis), flat-headed gudgeon (Philypnodon grandiceps), yellow-fin goby (Acanthogobius flavimanus), goldfish, carp and oriental weatherloach were also recorded (five to 23 individuals) (Table 3-5). In Gardiners Creek, the fish assemblage at the most downstream site (GC1) comprised approximately equal abundances of short-finned eel (33%), common galaxias (25%) and flat-headed gudgeon (23%) (Table 3-5, 3-6). At the second most downstream site (GC2) common galaxias and short-finned eel dominated the fish assemblage with relative abundances of 71% and 26% respectively (Table 3-5, 3-6). The fish assemblage at the midreach site (GC3) comprised approximately equal abundances of common galaxias (34%), goldfish (29%) and eastern gambusia (29%) (Table 3-5, 3-6). At the second most upstream site (GC4) eastern gambusia dominated the fish assemblage (75%) (Table 3-5, 3-6). The fish assemblage at the most upstream site (GC5) comprised approximately equal abundances of broad-finned galaxias (20%), eastern gambusia (40%) and oriental weatherloach (40%) (Table 3-6). In Back Creek, the fish assemblage was dominated by oriental weatherloach (59%) and short-finned eel (37%) (Table 3-5, 3-6). A single common galaxias was also recorded (Table 3-5). In Scotchmans Creek, the fish assemblage at the most downstream site (SC1) was dominated by common galaxias (93%), although short-finned eel, eastern gambusia and oriental weatherloach were also recorded (Table 3-5, 3-6). The fish assemblage at the mid-reach site (SC2) comprised approximately equal abundances of short-finned eel (27%), common galaxias (40%) and eastern gambusia (33%) (Table 3-5, 3-6). At the most upstream site on Scotchmans Creek (SC3), only one species, namely broad-finned galaxias, was recorded (Table 3-5). Department of Natural Resources and Environment Freshwater Ecology 22

28 Summary of species distribution Common galaxias were the most abundant species recorded, comprising 42% of the total fish fauna recorded, and were also one of the most widespread species, being recorded at six of the 10 survey sites (Table 3-5). In both Gardiners and Scotchmans creeks, the highest numbers of common galaxias were recorded from sites located in the lower reaches of the study area (GC1, GC2 and SC1) (Table 3-5). Short-finned eel comprised 17% of the total fish fauna recorded, and were also one of the most widespread species, being recorded at the six survey sites where common galaxias were recorded (Table 3-5). In Gardiners Creek, the highest numbers of short-finned eel were recorded from sites located in the lower reaches of the study area (GC1 and GC2) (Table 3-5). Broad-finned galaxias were recorded in relatively low numbers from the most upstream site on both Gardiners and Scotchmans creeks (GC5 and SC3) (Table 3-5). Flat-headed gudgeon were only recorded at the most downstream site on Gardiners Creek (GC1) and comprised 23% of the fish fauna recorded at this site (Table 3-5). Eastern gambusia were the most widespread species, being recorded at seven of the 10 survey sites, and comprised 19% of the total fish fauna recorded (Table 3-5). The majority (75%) of eastern gambusia were recorded at the second most upstream site on Gardiners Creek (GC4) (Table 3-5). Oriental weatherloach were recorded in relatively low numbers from three sites in the mid to upper reaches of Gardiners Creek (GC3, GC4 and GC5), the most downstream site in Scotchmans Creek (SC1) and Back Creek (BC1) (Table 3-5). The majority (70%) of oriental weatherloach were recorded at Back Creek (BC1) (Table 3-5). Goldfish were only recorded in relatively low numbers from sites located in the mid to upper reaches of Gardiners Creek (GC3 and GC4) (Table 3-5). Carp were only recorded at the second most upstream site on Gardiners Creek (GC4), comprising 18% of the fish fauna recorded at this site (Table 3-5). Yellow-fin goby were only recorded at the most downstream site on Gardiners Creek (GC1), comprising 15% of the fish fauna recorded at this site (Table 3-5). Department of Natural Resources and Environment Freshwater Ecology 23

29 Table 3-5. Total abundance of species recorded at sites on Gardiners, Scotchmans, Back and Damper creeks. Species GC1 GC2 GC3 GC4 GC5 BC1 SC1 SC2 SC3 DC1 Total Native fish species Anguilla australis* Galaxias brevipinnis* Galaxias maculatus* Philypnodon grandiceps Exotic fish species Acanthogobius flavimanus Carassius auratus Cyprinus carpio Gambusia holbrooki Misgurnus anguillicaudatus Decapod crustacea Cherax destructor Paratya australiensis Total number of individuals Total number of species Species present. * - Migrates between freshwater and marine habitats at some stage in life cycle. Department of Natural Resources and Environment Freshwater Ecology 24

30 Survey Effort Survey effort (time in hours) varied at each site depending on stream size and habitat complexity and ranged from 0.7 hours at Damper Creek (DC1) and the most upstream site on Scotchmans Creek (SC3) to 1.4 hours at the most downstream site on Gardiners Creek (GC1) (Table 3-6). The area of each survey reach also varied between sites (Table 3-6). Fish Density and Biomass Fish density was low at all sites ( fish.m -2 ), while fish biomass varied between sites ( g.m -2 ) with no apparent spatial trend (Table 3-6). In Gardiners Creek, fish biomass ranged from 0.03 g.m -2 at the most upstream site (GC5) to 50.5 g.m -2 at the second most upstream site (GC4) (Table 3-6). At the two most upstream sites on Gardiners Creek (GC4 and GC5), exotic species comprised the majority of fish biomass; carp comprised 99% at GC4, and oriental weatherloach comprised 61% and eastern gambusia 21% at GC5. At the three most downstream sites on Gardiners Creek (GC1, GC2 and GC3), short-finned eel comprised the majority of fish biomass; 98%, 99% and 74% respectively. In Back Creek (BC1), short-finned eel comprised the majority of fish biomass (95%). In Scotchmans Creek, fish biomass ranged from 0.2 g.m -2 at the most upstream site (SC3) to 6 g.m -2 at the mid-reach site (SC2) (Table 3-6). At all sites on Scotchmans Creek, native species comprised the majority of fish biomass; common galaxias comprised 66% at SC1, shortfinned eel 97% at SC2, and broad-finned galaxias comprised 100% at SC3. Catch Per Unit Effort Catch per unit effort (CPUE) varied between sites (0-92 fish.hr -1 ) (Table 3-6). In Gardiners and Scotchmans creeks, CPUE at the most upstream site on both creeks (GC5 and SC3) were similar (5.8-6 fish.hr -1 ). In Gardiners Creek, CPUE varied between sites with no apparent spatial trend (Table 3-6). In Scotchmans Creek, CPUE increased with increasing distance downstream from source, due to higher abundances of native migratory species in the lower reaches (Table 3-6). Department of Natural Resources and Environment Freshwater Ecology 25

31 Table 3-6. Survey effort and area of survey reach and catch statistics for survey sites within the study region. Creek and Site Effort (hrs) Area (m -2 ) Relative Abundance (%) Density (fish.m -2 ) Biomass (fish g.m -2 ) CPUE (fish.hr -1 ) Gardiners GC Af (15), Aa (33), Gm (26), Gh (3), Pg (23) GC Aa (26), Gm (71), Gh (3) GC Aa (4), Ca (29), Gm (34), Gh (29), Ma (4) GC Ca (6), Cc (18), Gh (75), Ma (1) GC Gb (20), Gh (40), Ma (40) Back BC Aa (37), Gm (4), Ma (59) Scotchmans SC Aa (1), Gm (93), Gh (1), Ma (5) SC Aa (27), Gm (40), Gh (33) SC Gb (100) Damper DC No fish Abbreviations denote species as: Af Acanthogobius flavimanus; Aa - Anguilla australis; Ca - Carassius auratus; Cc - Cyprinus carpio; Gb - Galaxias brevipinnis; Gm Galaxias maculatus; Gh - Gambusia holbrooki; Pg - Philypnodon grandiceps; Ma - Misgurnus anguillicaudatus. Department of Natural Resources and Environment Freshwater Ecology 26