Gunbower Forest Fish Monitoring Surveys: Autumn 2010

"July 2010".

Project Number: Gunbower Forest Fish Monitoring Surveys Autumn - M/BUS/353.

MDFRC item.

61 pages.

In March 2010, the North Central Catchment Management Authority (CMA) engaged The Murray-Darling Freshwater Research Centre (MDFRC) to undertake a survey of the Gunbower Island fish community. The objective of the survey was to investigate the current condition of the fish community at 21 sites across Gunbower Island. Survey sites included specific wetlands within Gunbower Forest (n=2), Gunbower Creek (n=7), lagoons (n=9) and the Murray River (n=3). In addition to the objectives listed in the project brief, this study took the opportunity to report against the objectives set for fish in The Living Murray Outcomes and Evaluation Framework (TLM OEF) for sites upstream of the Murray Mouth, Coorong and Lower Lakes, within which the Gunbower Island Icon Site is included (MDBC 2007). The TLM OEF provides a framework to measure condition of functional groupings of fish (below) relative to other TLM Icon Sites. Reporting against the listed objectives of the OEF will provide the North Central CMA with a measure of condition relative to the objectives of TLM. In line with the project brief and while considering the objectives of the TLM OEF, the current study endeavours to interpret observed fish population demographics (population size structure, spatial distribution and abundance) across the study area in view of populations shifting from or to ecologically sustainable levels. This report compares the condition of the Gunbower Island fish assemblage as it was surveyed in autumn 2010 to surveys of the same fish community conducted in 2009 by Rehwinkel and Sharpe (2009a).

A total of 25,321 fish from 16 species were encountered in the 2010 survey. The 11 native fish species encountered were Fly-specked hardyhead, Carp gudgeon, Flathead gudgeon, Dwarf flat-headed gudgeon, Australian smelt, Murray-Darling rainbowfish, Murray cod, Golden perch, Bony herring, Silver perch and Freshwater catfish. The 5 non-native species captured were Common carp, Goldfish, European perch or 'Redfin', Oriental weatherloach and Eastern gambusia or ‘Mosquito fish’. Trout cod were not recorded in the 2010 survey as they were in 2009. The native Carp gudgeon (Hypseleotris spp.) was ubiquitous and the most abundant species overall, followed by the exotic Eastern gambusia and native Flathead gudgeon which were present at most survey areas. This pattern was also observed in 2009. Common carp were the dominant large-bodied species recorded in all macrohabitat types except for Murray River sites, where Murray cod were more abundant. Juvenile Golden perch and Freshwater catfish were collected which suggests successful recruitment of these species in the Gunbower region. Progress toward the TLM OEF objective ‘…sustainable populations of Murray cod, golden perch and catfish and restrict populations of common carp…’ has been made, with similar numbers of Murray cod collected in Gunbower Creek as compared to previous surveys, along with a number of juvenile and sub-adult individuals in the Murray River and the ongoing presence of Freshwater catfish on Gunbower Island. Golden perch appeared to have successfully recruited in 2010, however, their overall abundance across Gunbower Island remain relatively low. Common carp showed an increase in relative abundance in 2010, but compared to a survey conducted in 2007, their relative abundances was low.