Fish assemblages, movement and recruitment in the Chowilla anabranch system

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1 Fish assemblages, movement and recruitment in the Chowilla anabranch system Brenton Zampatti, Sandra Leigh, Ian Magraith, Chris Bice Inland Waters Program, SARDI Aquatic Sciences

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3 Three broad components 1. Determine the distribution and community structure of fish assemblages in Chowilla 2. Investigate aspects of the ecology of fishes in the Chowilla system, particularly Murray cod and callop 3. Assess the impact of high priority barriers on fish passage in the Chowilla system

4 Fish distribution and community structure Boat electrofishing undertaken at 20 sites throughout the Chowilla system in March 2005 and x 90s shots at each site Sites in all creeks (fast and slow flowing), backwaters River Murray

5 Monoman Punkah SA NSW border Chowilla Boat Pipeclay Slaney Salt Murray Bank I Hypurna

6 Native Fish Fish distribution and community structure Common name Scientific name Total no. Bony bream Nematalosa erebi 6,497 Unspecked hardyhead Craterocephalus stercusmuscarum fulvus 6,489 Australian smelt Retropinna semoni 2,768 Murray rainbowfish Melanotaenia fluviatilis 1,520 Carp gudgeons Hypseleotris spp 1,031 Flatheaded gudgeon Phylipnodon grandiceps 548 Callop Macquaria ambigua 414 Murray cod Maccullochella peelii peelii 53 Silver perch Bidyanus bidyanus 11 Dwarf flatheaded gudgeon Phylipnodon sp 4 Freshwater catfish Tandanus tandanus * Exotic fish Common carp Cyprinus carpio 718 Goldfish Carassius auratus 339 Gambusia Gambusia holbrooki 257 Total 20,649

7 Fish distribution and community structure Most small bodied species and bony bream, callop and carp are widespread throughout the system Murray cod are only found in creeks with good habitat (e.g. snags) and high flows Chowilla, Slaney, Pipeclay, Boat and Swiftys Most diverse sites: Slaney, Pipeclay, Chowilla, Swiftys, River Murray Least diverse sites: Slaney Backwater and Pilby

8 Fish distribution and community structure Good size range of most species indicates some level of recruitment Subsample of callop being aged (otoliths) PIT tags being inserted in Murray cod, callop, silver perch and carp

9 Spawning and recruitment of fish in Chowilla 1. Spatial and temporal distribution of larval fish 2. Length and age frequency of selected species

10 Spawning and recruitment of fish in Chowilla Fortnightly larval sampling September - March Increased sampling effort in 05/06 8 creeks 3 drift nets and 3 light traps per creek Punkah Salt Chowilla Boat Pipeclay Slaney Murray Hypurna

11 Spawning and recruitment of fish in Chowilla Larvae of small bodied species dominate catch No Murray cod or callop larvae in 04/05 Catfish larvae collected in Slaney Creek and the River Murray Murray cod and callop larvae in Chowilla, Pipeclay, Boat and Punkah creeks in 05/06

12 Recruitment ecology of fishes in Chowilla Murray cod larvae in fast flowing creeks and Chowilla creek Some callop larvae in slow flowing creeks Greater abundance of carp larvae in 05/06

13 Flow to SA (Jan 04 Jan 06) Flow ML/d Jan 04 Apr 04 Jul 04 Oct 04 Jan 05 Apr 05 Jul 05 Oct 05 Jan 06

14 0.08 carp callop 0.14 Recruitment of fishes in Chowilla n = n = 162 Frequency Length frequency and age structure Total length (mm) Frequency n = 7 n=45 Frequency Length (mm) Length (mm) silver perch Murray cod Frequency n = Age (years) Length (mm) Length (mm)

15 Length (mm) (a) Lock 6-7 n = (b) Chowilla n = (c) Lock n =

16 Impact of barriers Generally recognised that callop, silver perch and Murray cod may undertake extensive migrations, most likely for spawning Recent investigations show that many small bodied fish also migrate Barriers to movement have been implicated in the decline of native fish populations

17 Impact of barriers Sites Four electrofished most common downstream species collected of Slaney, in Punkah higher Pipeclay and Lock abundances 6 weirs Chowilla (once downstream a month, of October weirs Dec and March) Salt Boat Pipeclay Slaney Murray Hypurna

18 Mean Mean # individuals # individuals / minute / minute electrofishing elctrofishing Mean # individuals / minute elctrofishing Mean # individuals/minute electrofishing October October October Weir Sites Reference Sites Weir sites Reference Sites November November November December December March March Australian Bony Callop Bream Smelt Unspecked hardyhead October October November November December December December March March March Weir Sites Weir Sites Reference Sites Reference Sites October October October November November November December December December March March March Sites 1 Sites Sites 6 Sites 1 & 2 Sites 3 & 4 Sites 5 & 6 Sites Sites 1 1 & & 2 2 Sites Sites 3 & 4 Sites Sites 5 & 6

19 Callop Movement Study Punkah Chowilla Boat Pipeclay Slaney Murray

20 Callop movement Strong site fidelity Considerable medium scale (10-20 km) movement during elevated water levels (spring/early summer) Movement into 2º anabranches and backwaters Lock 7 18/2/06 Large scale movements (>200 Lock 9 km) 30/3/06 January-March

21 What does it all mean? Chowilla anabranch system is a microcosm of what the Lower River Murray once was. Diverse habitats provide areas for spawning, rearing and residency for large and small bodied fish. Need to ensure these habitats are maintained and protected. Maintaining connectivity between habitats is essential By developing an understanding of the ecology of fishes in Chowilla we can advise on how best to deliver environmental flows, mitigate barriers to fish passage and conserve/restore aquatic habitats

22 Thanks to Nick Whiterod and Anthony Conallin (MDFRC, Mildura), and Paul Jennings, David Short and Matt Pellizarre (SARDI)