Trial trout recreational fishery in Lake Kerferd and Lake Sambell: surveys for community structure and trout cod survival

Paul Brown

November 2010 Fisheries Victoria Department of Primary Industries

If you would like to receive this Copyright © The State of Victoria, Department of information/publication in an Primary Industries, 2010. accessible format (such as large This publication is copyright. No part may be print or audio) please call the reproduced by any process except in accordance Customer Service Centre on: with the provisions of the Copyright Act 1968. 136 186, TTY: 1800 122 969, Authorised by the Victorian Government, 2a Bellarine Hwy, Queenscliff, Victoria 3225 or email Printed by Fisheries Victoria, Queenscliff, [email protected] Victoria Published: Fisheries Victoria Department of Primary Industries, Queenscliff Centre Preferred way to cite: PO Box 114, Queenscliff, Victoria Brown, P. (2010) Trial trout cod recreational 3225 . fishery in Lake Kerferd and Lake Sambell: surveys for community structure and trout cod survival. Fisheries Victoria Internal Report No 29, General disclaimer 14 pages. Department of Primary Industries, This publication may be of assistance to you but Snobs Creek, Victoria, Australia. the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

Trout cod recreational fishery development ii

Executive Summary

Fisheries Victoria has implemented a project to index (CPUE) for each gear type to compare create a recreational fishery for trout cod by relative abundance between lakes and allow for stocking fingerlings into Lake Kerferd and Lake future comparisons. Fish species were classified Sambell in North East Victoria. relative to the ecological niche of trout cod as predators, competitors, or prey. Relative abundance The objectives of this study are: of each ecological class was calculated and 1. to monitor the survival and growth of trout compared for each lake. cod as the populations develop Trout cod relative abundance more than doubled 2. to determine predator‐prey relationships. between 2009 and 2010 surveys of Lake Kerferd. This interim report documents the first two In Lake Kerferd, the potential for predation on, annual monitoring surveys during 2009 and and competition with trout cod was lower; while 2010, and describes the fish community the relative abundance of prey items was higher composition and aspects of the fish ecology in than in Lake Sambell. 2009. Both lakes have large populations of golden Fish community surveys used electrofishing, perch (Macquaria ambigua) following the previous mesh‐nets, fyke‐nets, bait‐traps and opera‐house stock enhancement of this popular recreational nets to sample a wide range of fish and species. Estimates of length at age for a sample of . from each lake showed that they were growing relatively slowly for this species. Trout cod survivors from all stocking events Golden perch, and to a lesser extent, redfin are were observed in Lake Kerferd along with eight presently the main large fish predators and other fish species. Prior to re‐stocking with trout potential future‐competitors for trout cod in cod, four fish species were also sampled in Lake these lakes. Sambell. Crustaceans such as shrimp and yabbies were not abundant in either lake. Sampling effort was standardised and relative abundance calculated as a catch‐per‐unit‐effort

Trout cod recreational fishery development iii

Trout cod recreational fishery development iv

Table of Contents

Executive Summary...... iii

Introduction...... 1 Background...... 1 Trial Design...... 1 Monitoring events ...... 1 This report...... 2

Material and Methods ...... 3 Predator‐prey relationship in Lake Kerferd and Lake Sambell...... 3

Results...... 5 Predator‐prey relationship in Lake Kerferd and Lake Sambell...... 5 Survival and growth of trout cod in Lake Kerferd ...... 5

Discussion...... 11 Predator‐prey relationship in Lake Kerferd and Lake Sambell...... 11 Survival and growth of trout cod in Lake Kerferd ...... 11 Conclusions...... 12

Acknowledgments...... 13

References ...... 14

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List of Tables Table 1. Stocking history of lakes Kerferd and Sambell...... 1 Table 2. Sample size and average size of fish and decapod crustaceans sampled from Lake Kerferd in 2009...... 7 Table 3. Sample size and average size of fish and decapod crustaceans sampled from Lake Sambell...... 7 Table 4. Classification of species of fish and decapod from lakes Kerferd and Sambell according to their potential as predator, competitor or prey of stocked trout cod ( macquariensis)...... 7 Table 5. Catch per unit effort (CPUE) during surveys of fish and crustaceans at Lake Kerferd and Lake Sambell for five types of gear in 2009. CPUE for mesh nets, fyke nets, bait traps and opera house traps calculated as fish per net per hour (see Equation 1) and CPUE for electrofishing calculated as fish per 60‐seconds of machine on‐time (see Equation 2)...... 8 Table 6. Total catch per unit effort (CPUE) during surveys of fish and crustaceans at lakes Kerferd and Sambell for each species...... 9

List of Figures Figure 1. Length at age for trout cod sampled from Lake Kerferd following three stocking events. Dashed lines indicate approximate growth trajectories fitted by eye to each year‐class. n=number of fingerlings stocked at an approximate size of 50 mm TL. Fish recaptured from each stocking event were n=2 from year class of 2008, n=12 from year class of 2009 and n=1 from year class of 2010...... 9 Figure 2. Length at age estimates for golden perch sampled from Lake Kerferd and Lake Sambell in comparison with those from other Victorian lakes. Estimates were based on n=5 fish from Lake Kerferd and n=14 fish from Lake Sambell...... 10

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Introduction

• Undertake a stock assessment to evaluate the Background trial and return from stocking. Trout cod (Maccullochella macquariensis) is a • freshwater fish that is endemic to the Murray‐ Undertake a series of monitoring events: Darling River system in south‐eastern Australia o to provide a snapshot of each lakes’ fish (Trout cod recovery team 2008b). In Victoria, and invertebrate community trout cod were believed to have once been widely composition spread across the streams of the north‐central o to determine the status of the stocked and north‐eastern Victoria that flow into the trout cod population . o and once the fishery is open, to Across its natural range this species has suffered investigate angler catch rates, angler a catastrophic decline in abundance. In Victoria satisfaction and angler awareness of there is only one known self‐sustaining trout cod conservation issues. population of trout cod (DPI 2010). Trout cod were listed as an endangered species under the Trout cod stocking history Environmental Protection and Biodiversity The stocking history of Lake Kerferd and Lake Conservation Act 1999, because of this decline in Sambell is summarised in Table 1. both range and abundance (Trout cod recovery On each occasion, the fingerlings were released team 2008b). at the dam wall at Lake Kerferd and the boat A National Recovery Plan was developed listing ramp at Lake Sambell (E. Mclean, Department of the recovery objectives and actions necessary to Primary Industries (DPI) FV, pers. comm.). ensure the long term survival of the species Releases occurred between 10:30 and 12:00 h for (Trout cod recovery team 2008b). Recovery both lakes. objective No. 12 recommended ‘trialling the development of a recreational fishery for stocked Table 1. Stocking history of lakes Kerferd and trout cod in Victoria’ pending the: Sambell. • Identification of suitable impoundments Year Lake Kerferd Lake Sambell (lakes or dams) Number Mean Number Mean • Level of interest of recreational fishing stocked weight stocked weight bodies in the development of this type of (g) (g) fishery (Trout cod recovery team 2008b). 2008 300 0.3 0 ‐ As the trial concept was supported by significant 2009 2,280 0.8 0 ‐ stakeholder groups (e.g. Native Fish Australia & 2010 3,500 0.9 3,500 0.9 VRFish) and received full support at Fisheries Victoria regional fisheries stakeholder meetings, Fisheries Victoria (FV) initiated the trial in two Monitoring events suitable impoundments, Lake Kerferd and Lake Sambell, located near Beechworth in Victoria’s Scientific monitoring of Lake Kerferd and Lake northeast. Sambell commenced in 2009 (this study) to answer the following key questions: Trial Design. 1. What are the predator/prey relationships? Trout cod will be stocked into the impoundments 2. Will stock enhancement work? as fingerlings and it will likely be several years 3. How many, how often and what size of fish before the fishery can be opened for recreational should be stocked? fishing. The research objectives are: Essential components of the trial are: • Determine the predator/prey relationships • Stock the lakes for four consecutive years that exist in Lake Kerferd and Lake Sambell. with hatchery reared trout cod fingerlings

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• Determine the status of the stocked trout cod population over time – survival and where possible growth • Determine the most appropriate stocking strategy for L. Kerferd (and L. Sambell) (stocking density, size at stocking and frequency & duration of stocking). A fishery‐dependant assessment methodology to observe actual fishing‐effort, catch and harvest levels may also be developed appropriate to the level of interest and participation in the fishery. This report This interim report addresses the first two of the research objectives through surveys of the two lakes in 2009 and 2010: • The 2009 survey provides the data to identify potential predators and prey of trout cod • Both surveys provide data to assess the survival (e.g. presence and number) of the year‐classes of trout cod stocked into Lake Kerferd in 2008, 2009 and 2010.

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Material and Methods

age determination techniques were used to count Predator‐prey relationship in annual growth increments in thin sections cut Lake Kerferd and Lake Sambell through otoliths. Sampling period Relative abundance (CPUE indices) Lake Kerferd was sampled in January and Indices of catch‐per‐unit‐effort (CPUE) were February 2009, and Lake Sambell was sampled in developed for each gear‐type, so that relative April 2009. abundances of fish and invertebrate species Sampling Approach could be compared. Gear deployed Although the gear was comparable at both Comparable fishing gear was used in each locations, the exact fishing effort varied slightly location. Fish and invertebrate surveys used due to: traps, mesh nets, fyke nets and electrofishing to • different ‘soak‐times’ for nets and traps sample the species‐composition and relative • differences in electrofishing time with abundance of predator, competitors and prey of duration that power was applied to the water trout cod machine ‘on‐time’ was recorded as 1620 Nets and traps seconds and 1561 seconds for lakes Kerferd Nets and traps were deployed overnight twice and Sambell, respectively for Lake Kerferd, and a single night for Lake • two net‐nights in Lake Kerferd, as opposed Sambell. to one net‐night in Lake Sambell. Five mesh nets (2.5, 3, 3.5 inch stretch‐mesh), ten To standardise the catches in terms of their fyke nets (5 m single‐wing 25 mm stretch mesh relative abundance for each lake two standard with 10 mm stretch mesh cod‐end), ten standard indices were calculated: ‘opera‐house’ yabby traps, and ten collapsible 1) catch per hour of soak‐time, for nets and bait‐traps were used on each occasion. traps (cpuenetting) (Equation 1). Electrofishing A separate cpuenetting value was calculated for Electrofishing with a boat‐based electrofisher each type of net or trap. unit (Smith‐Root 7.5 GPP) was undertaken during daylight hours for two hours on each CPUEnetting = C/h/g lake. Data collected Equation 1. Species identification, weight and number Where C=catch, h=soak time in hours and All observed fish were collected, identified, g=number of pieces of gear (i.e. nets, yabby traps weighed (g) where possible, and measured (fork or bait traps) length (FL) or total length (TL) depending on 2) catch per 60 seconds ‘machine on‐time’ for species, mm). Fish weights were not obtained at electrofishing (cpueelectro) (Equation 2). Lake Sambell 2009 due to a malfunctioning balance. CPUEelectro = C/s× 60 Yabbies (Cherax destructor) were measured (carapace length, mm) and shrimp Equation 2. (Macrobrachium australiense) were counted and Where C=catch, s=machine on‐time in seconds. weighed. Where possible, fish were returned alive to the water. Growth rates of golden perch were also examined. Age was estimated for a small sample of golden perch that died in the sampling process from Lake Kerferd and Lake Sambell. Standard

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Ecological classification Survival and growth of trout cod in Fish (other than trout cod) and decapod Lake Kerferd crustaceans encountered in the surveys of lakes The electrofishing data on trout cod collected in Kerferd and Sambell were classified as potential 2009 as part of the ecological snapshot of predators, competitors and prey of the trout cod. predator/prey relationships in Lake Kerferd This classification is based on the known biology provided information on the growth and survival and ecology of trout cod detailed by the National of the 2008 and 2009 stocked year classes. Recovery Team. For this classification: A second electrofishing survey to provide • species are labelled as a ‘predator’ if they are information on the growth and survival of likely to prey on trout cod at any life‐history stocked trout cod from the stocked year class of stage (fingerlings to adults) 2009 was completed in Lake Kerferd in March • species are labelled as a ‘competitor’ if their 2010. Two hours of electrofishing (1704 seconds diet at any life‐history stage is likely to machine time) was recorded. display significant overlap with trout cod at Researchers looked for the presence of surviving any life‐history stage trout‐cod from any of the stocked year‐classes, • species labelled as ‘prey’ are likely to form and recorded size (mm, TL) and weight (g) for part of the preferred diet of trout cod at any those that could be sampled. life‐history stage All sampled trout cod were then returned alive to For example, golden perch are classed as the water. potential predators and competitors, while yabby are classed as prey. The relative abundance of potential predators, competitors and prey of trout cod in each lake was examined by summing the CPUE data as indices of abundance for each classification. For this analysis species considered predators were classified as competitors.

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Results

classification, shows that indices of Predator‐prey relationship in predation/competition and prey were similar for Lake Kerferd and Lake Sambell each lake: Overall catch • The predation/competition index at Lake Eleven species of fish and decapod crustaceans Kerferd was CPUEpred=1.4 cf CPUEpred=1.8 at were sampled. Eight fish species were sampled Lake Sambell. from Lake Kerferd (Table 2), and four fish and • The prey index was CPUEprey=1.3 at Lake two decapod crustacean species from Lake Kerferd cf CPUEprey=1.1 at Lake Sambell. Sambell (Table 3). Golden perch growth Ecological Classification of Species Age was estimated for five golden perch Present (311mm–438 mm, TL) from Lake Kerferd, and for Species of fish and crustaceans sampled in 14 golden perch (319 mm–425 mm, TL) from surveys of Lake Kerferd and Lake Sambell were Lake Sambell (Figure 2). Age estimates ranged 3– classified as potential ‘competitor’, ‘predator’ and 8 years for Lake Kerferd, and 5–13 years for Lake ‘prey’ of trout cod (Table 4). Sambell. Lake Kerferd potentially had six predatory, five Figure 2 also compares the age and length of competitive and five prey species. golden perch from Lake Kerferd and Lake Sambell with those of golden perch from other Lake Sambell potentially had two predatory, two Victorian Lakes. Golden perch growth rate for competitive and four prey species. both Lake Kerferd and Lake Sambell is low Relative abundance compared to most other Victorian populations. The relative abundance (CPUE) of each species sampled, by gear type is presented in Table 5, Survival and growth of trout cod and by species in Table 6. Lake Kerferd was the in Lake Kerferd only one of these lake stocked with trout cod at the time of the survey (2009). Trout cod 2009 On 25 February 2009, four trout cod were These standardised indices of abundance can be electrofished from along the dam wall at Lake used to compare the aquatic fauna communities Kerferd (Figure 1). between lakes: The size distribution of these individuals • Both lakes have similar and high abundances suggests that: of golden perch (0.986 for Lake Kerferd and • 0.878 for Lake Sambell). two were survivors from the 2008 stocking (155 and 172 mm TL, 44 and 61 g) • Lake Sambell has a relatively higher • abundances of redfin and tench compared two were survivors from the very recent 2009 with Lake Kerferd (0.911 cf 0.248 and 0.375 cf stocking (63 and 68 mm TL, 4 and 5 g)). 0.082 respectively) Trout cod 2010 • Lake Kerferd has a relatively high abundance On 17 March 2010, eleven trout cod were of southern pygmy perch, goldfish and sampled by electrofishing along the dam wall at mosquito fish, than Lake Sambell (0.407 cf Lake Kerferd. 0.00; 0.315 cf 0.179 and 0.333 cf 0.000 respectively) • Shrimp and yabbies were detected at Lake Sambell, but not Lake Kerferd. • and brown trout were detected at Lake Kerferd, but not in Lake Sambell. Summing the CPUE data by species and gear‐ type, and grouping the results by ecological

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The size distribution of these individuals suggests that • one was a survivor from the recent 2010 year‐ class (66 mm TL, and 2 g) • ten were survivors from the 2009 year‐class (131–175 mm TL, 22–62 g) (Figure 1). In addition to those sampled, at least 20 young‐ of‐year trout cod were observed within the rocky substrate of the dam‐wall, but were unable to be collected. The relative abundance of trout cod in Lake Kerferd in 2010 was 0.38, compared to 0.148 in 2009.

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Table 2. Sample size and average size of fish and decapod crustaceans sampled from Lake Kerferd in 2009.

Species Count Average Length (mm) Average Weight (g) trout cod (Maccullochella macquariensis) 4 115 29 golden perch (Macquaria ambigua) 59 254 263

Murray cod (Maccullochella peelii peelii) 1 385 834 goldfish (Carassius auratus) 14 158 140 redfin (Perca fluviatilis) 11 132 73 tench (Tinca tinca) 15 432 1227 brown trout (Salmo trutta) 2 397 845 southern pygmy perch (Nannoperca australis) 65 31 1* mosquito fish (Gambusia affinis) 9 32 1* yabby (Cherax destructor)* 1 33 13

*Approximate weight, balance will not register fish of less than 1g

Table 3. Sample size and average size of fish and decapod crustaceans sampled from Lake Sambell. Species Count Average Length (mm) golden perch 35 394 goldfish 6 281 redfin 28 98 tench 22 392 shrimp (Macrobrachium australiense) 2 20 yabby 1 31

Table 4. Classification of species of fish and decapod crustacean from lakes Kerferd and Sambell according to their potential as predator, competitor or prey of stocked trout cod (Maccullochella macquariensis). Species Lake Kerferd or Predator Competitor Prey Sambell trout cod K, S ; ; golden perch K, S ; ; Murray cod K ; ; redfin K, S ; ; ; tench K, S ; brown trout K ; ; southern pygmy perch K ; mosquito fish K ; ; goldfish K,S ; shrimp S ; yabby K,S ;

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Table 5. Catch per unit effort (CPUE) during surveys of fish and crustaceans at Lake Kerferd and Lake Sambell for five types of gear in 2009. CPUE for mesh nets, fyke nets, bait traps and opera house traps calculated as fish per net per hour (see Equation 1) and CPUE for electrofishing calculated as fish per 60‐seconds of machine on‐time (see Equation 2). Fishing gear Species Lake Lake Kerferd Sambell CPUE CPUE

Mesh‐nets golden perch 0.183 0.225 tench 0.080 0.163 redfin 0.023 0.000 Murray cod 0.006 0.000 brown trout 0.011 0.000 goldfish 0.011 0.025

Bait Traps southern pygmy perch 0.185 0.000 tench 0.000 0.005 shrimp 0.000 0.011

Fyke nets golden perch 0.012 0.000 tench 0.002 0.011 redfin 0.002 0.027 goldfish 0.007 0.000

Opera House traps golden perch 0.050 0.000 tench 0.000 0.004 yabby 0.000 0.004

Electrofishing golden perch 0.741 0.653 trout cod 0.148 0.000 redfin 0.222 0.884 goldfish 0.296 0.154 mosquito fish 0.333 0.000 southern pygmy perch 0.222 0.000 tench 0.000 0.192

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Table 6. Total catch per unit effort (CPUE) during surveys of fish and crustaceans at lakes Kerferd and Sambell for each species. Species Lake Kerferd Lake Sambell Total CPUE Total CPUE

trout cod 0.148 0.000 golden perch 0.986 0.878 Murray cod 0.006 0.000 redfin 0.248 0.911 brown trout 0.011 0.000 goldfish 0.315 0.179 southern pygmy perch 0.407 0.000 tench 0.082 0.375 mosquito fish 0.333 0.000 shrimp 0.000 0.011 yabby 0.000 0.004

200

180

160 age 1+ 140

120 Stocking event Year class 2008 100 Year class 2009

80 year class 2010 Length (mm, TL) (mm, Length

60 age 0+ n=300 n=2280 n=3500 40

20

0 11/2007 02/2008 06/2008 09/2008 12/2008 03/2009 07/2009 10/2009 01/2010 05/2010 Date (mm/YYYY)

Figure 1. Length at age for trout cod sampled from Lake Kerferd following three stocking events. Dashed lines indicate approximate growth trajectories fitted by eye to each year‐class. n=number of fingerlings stocked at an approximate size of 50 mm TL. Fish recaptured from each stocking event were n=2 from year class of 2008, n=12 from year class of 2009 and n=1 from year class of 2010.

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600

500

400 Albert Park Kerang lakes 300 LakeEppalock Lake Kerferd Lake Sambell Length (mm,TL)Length 200

100

0 02468101214 Age (years)

Figure 2. Length at age estimates for golden perch sampled from Lake Kerferd and Lake Sambell in comparison with those from other Victorian lakes. Estimates were based on n=5 fish from Lake Kerferd and n=14 fish from Lake Sambell.

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Discussion

• intra‐specific competition caused by high Predator‐prey relationship in population abundance in relation to the food Lake Kerferd and Lake Sambell resources available Potential prey supply for trout cod • cooler than optimal water temperatures for Trout cod fingerlings probably have similar diet growth of golden perch at the ~550 m to juveniles which includes a wide range of elevation of both lakes. zooplankton and aquatic (Trout cod Competition for food with golden perch for older recovery team 2008a). Sufficient small food‐items trout cod may be a significant factor for the are likely to be available for stocked fingerlings establishment of a viable trout cod fishery. in most healthy lake ecosystems during summer. Predators As trout cod juveniles grow, they switch to larger Golden perch are likely to be the dominant prey‐items that are more energy efficient for a predators on trout cod fingerlings in both lakes. larger fish to collect (Trout cod recovery team 2008a). The diet of trout cod averaging almost The preferred diet of golden perch also shows 300 mm TL in the Murrumbidgee River was considerable overlap with trout cod dominated by macro‐crustaceans, such as (Baumgartner 2007). Although both species yabbies, shrimps and spiny crayfish prefer crustacean prey, they will also eat small (Baumgartner 2007). Fish, aquatic insects and fish. Since crustacean densities are low, the larger terrestrial organisms were also eaten by some golden perch may utilise the stocked trout cod as trout cod but in much lower proportions. prey. Ideally, the trout cod stocked at Lake Kerferd and As a long‐lived species, existing golden perch in Lake Sambell should have an abundant Lake Kerferd and Lake Sambell have the population of shrimp and yabbies to prey upon. potential to continue to compete with larger trout The fish community surveys specifically used cod for a decade or more. gear designed to catch shrimps and yabbies (e.g. Limited food resources may depress trout cod bait‐traps and opera‐house nets). Neither of these growth rates which in turn may reduce their crustaceans were sampled in Lake Kerferd and survival. Small fish are more vulnerable to gape‐ CPUE was very low in Lake Sambell. This limited predators (such as fish and birds). Slow‐ suggests that the density of crustaceans as growing individuals remain vulnerable to these potential prey for a developing trout cod types of predators longer than faster‐growing population is very low. individuals. Potential for predation and competition While redfin are also piscivorous (Baxter et al. Competitors 1985; Molony et al. 2004), and were present in Trout cod’s preference for crustaceans as prey both waterways, large redfin were uncommon in items is also shared by golden perch. comparison to golden perch. This species, in low Golden perch were the most abundant mid‐sized abundance is thought to pose a low a low risk to the establishment of a trout cod fishery. predator in Lake Kerferd and Lake Sambell. The lakes contained a relatively high abundance of However the capacity of redfin to reproduce golden perch, which may explain the lack of rapidly within small lakes such as Lake Kerferd and Lake Sambell means that the potential exists shrimps, yabbies and spiny crayfish in both lakes. for a large biomass of competing predators to develop. Golden perch are predators with a crustacean preference which have the potential to directly Survival and growth of trout cod compete with the establishing trout cod for food. in Lake Kerferd Analyses of golden perch growth in both Lake Trout cod were sampled from all stocking events Kerferd and Lake Sambell shows these fish are (2008, 2009 and 2010) which suggests some level growing slowly and are relatively small for their of survival from each. age. This could be due to:

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The data from surveys in 2009 showed low relative abundance of trout cod at the stocking Conclusions site (the dam wall). Further sampling in 2010 The initial snapshot surveys indicated golden indicated relatively good survival to age 1+, for perch was the major potential predator and the 2009 year‐class. competitor of trout cod present in both lakes. The preferred crustacean prey of older trout cod was No fish of the 2008 cohort aged 2+ were found in limited in both lakes. the 2010 survey. This result might be a result of: • Strong dispersal of these fish to other Golden perch were present in both Lake Kerferd locations within the lakes and Lake Sambell in sufficient numbers to potentially pose a risk to the establishment of a • The small number of fish stocked in 2008 trout cod fishery. (n=300) • Low sampling efficiency Golden perch have the potential to: • Poor survival of stocked trout cod past 1+ • Prey directly on trout cod fingerlings age class. • Compete with older trout cod for the limited crustacean prey resource in the lakes. Annual surveys in 2009 and 2010 in Lake Kerferd demonstrated: • Trout cod fingerlings survived at least one year after the first two stocking events. Further monitoring in Lake Kerferd and Lake Sambell is planned to monitor the establishment of trout cod populations. Results of these future surveys will direct future fisheries management action to develop viable trout cod recreational fisheries in the lakes.

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Acknowledgments

This research was conducted under DPI Fish Ethics Committee Permit Sept08 0057.

Thanks to Taylor Hunt, Cameron McGregor,

Daniel Steel and John Douglas (DPI) for assistance with the fish sampling and to the North East Water and the Indigo Shire for facilitating access to these waterways. Thanks also to Taylor Hunt for comments on the draft of the manuscript.

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References

Baumgartner, L. J. (2007). Diet and feeding habits of predatory fishes upstream and downstream of a low‐level weir. Journal of Fish Biology 70, 879‐894. Baxter, A. F., Vallis, S. L., and Hume, D. J. (1985). The predation of recently released rainbow trout fingerlings Salmo gairdneri by redfin Perca fluviatilis in Lake Burrumbeet, October‐December 1983. Trout cod recovery team (2008a). Background and Implementation Information for the Trout Cod Maccullochella macquariensis. National Recovery Plan Department of Sustainability, Melbourne.

Trout cod recovery team (2008b). National Recovery Plan for the Trout Cod Maccullochella macquariensis. Department of Sustainability, Melbourne.

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