Fish and fish habitats of the Pike River anabranch and floodplain complex

"March 2010".

Project Number: Fish and Fish Habitats of the Pike River Anabranch and Floodplain Complex - MBUS|309.

MDFRC item.

Spatial segregation of species, due to differences in habitat use, is important for the health and structure of fish communities. River regulation in the Murray-Darling Basin has resulted in alerted flow regimes, restrictions to fish movement and decreases in available habitat for fish. In the South Australian River Murray, off-channel habitats such as Chowilla, Katarapko and the Pike Anabranch systems may provide important habitat for fish.The Pike Anabranch system consists of a series of creeks, backwaters and lagoons extending over 4,000 ha of floodplain, between the townships of Paringa and Lyrup, in South Australia. The aim of this study was to assess the fish populations and aquatic habitats in the Pike Anabranch system. The specific objectives were to: Determine the distribution and community structure of fish assemblages in the Pike Anabranch system; Determine the distribution and community structure of in-stream habitat in the Pike Anabranch system; and Investigate the relationship between fish assemblages, micro-habitat and meso-habitats (flow types).A total of 16 sites were assessed across the Pike Anabranch system, including three in the main channel of the River Murray. Fish were sampled using an electro-fishing approach and detailed habitat assessments were undertaken at each fish survey site. Quantitative habitat assessments were also carried out for every 90-second electrofishing shot to allow analysis of fish-habitat associations. During the survey, a total of 4138 fish were collected in the Pike Anabranch system and adjacent River Murray representing nine native and four non-native species. The most abundant species were bony herring Nematolosa erebi (n=1524), un-specked hardyhead Craterocephalus stercusmnuscarum fulvus (n=1424), goldfish Carassius auratus (n =442), common carp Cyprinus carpio (n =237) and Australian smelt Retropinna semoni (n =181). Two fish species of specific conservation interest were also captured in low abundance, freshwater catfish Tandanus tandanus and silver perch Bidyanus bidyanus. Both species are protected under the South Australian Fisheries Management Act 2007. Overall, fish species richness was comparatively lower than the species richness recorded in the off-channel habitats of Katarapko and Chowilla Anabranch systems. In addition, the fish community composition of the Pike Anabranch system did not differ between meso-habitat types.In general, riparian habitat within the Pike Anabranch system was poor condition, while in-stream habitat was relatively good and dominated by native taxa. Only a few habitat associations were revealed in some fish species, which may relate to the lack of distinct habitat types in this anabranch system, i.e. low habitat heterogeneity. Generally, the system appears to provide conditions supporting an increase presence of non-native fish species, as opposed to native species, hence the Pike Anabranch system may provide a good template for a habitat restoration approach. Floodplain management activities within the Pike Anabranch systems, such as increasing connectivity and flowing habitats, may facilitate increase native fish diversity and abundance, by increasing the diversity of micro- and meso-habitats.