Penrith Lakes Fish Scheme - 2009 Fish Monitoring Program
Knight JT (2010) Penrith Lakes Fish Scheme – 2009 Fish Monitoring Program. Industry & Investment NSW – Fisheries Research Report Series No. 25. ISSN 1837-2120. 69pp.
The Penrith Lakes are a series of artificially constructed water bodies located on the Nepean River floodplain west of Sydney that are managed by the Penrith Lakes Development Corporation. Native fish communities play a key role in the development of the lake environments, as well as providing recreational fishing opportunities through the stocking of Australian bass. Within the framework of ongoing assessments of the status of fish communities, Industry & Investment NSW (I&I NSW) was commissioned to assess the types, numbers and sizes of fish within the permanently connected Warm-up and Regatta Lakes, (collectively termed the SIRC Lakes), and Main Lake A, Duralia Lake, Middle Basin, Cranebrook Lake and North Pond. In addition, the biology of Australian bass in the SIRC Lakes and Duralia Lake was examined to provide insights into the health of the stocked populations.
A total of 9,273 fish belonging to 11 species, 181 freshwater prawns and 3,530 freshwater shrimp were sampled on 2 – 10 February 2009. Overall, the seven surveyed lakes appeared to have relatively healthy, functioning aquatic ecosystems. Water quality was generally good and there was an abundance of aquatic life including a good supply of small forage fish and crustaceans to sustain larger predatory species such as bass and eels. The types of fish present have also remained relatively stable over the last four years with no apparent disappearances or new occurrences of fish species but there were substantial increases in the numbers of some of the native fish caught in 2009 compared to 2008 and 2007.
The survey results also indicated that most populations of native fish were breeding and hence self-sustaining as evidenced by the capture of both juvenile and adult fish. Unfortunately, the same was true for the alien eastern gambusia, which was caught in much larger numbers in most lakes in 2009 than in the previous two years. Relatively large numbers of alien common carp were also caught in Main Lake A and North Pond, whereas carp numbers appeared to be on the decline in the SIRC Lakes. Unfortunately, catches of native fish from Regatta Lake had also declined in size. The size of the bass catches varied considerably among the lakes. The largest catch of bass came from Middle Basin while none were caught from Cranebrook Lake indicating that the stocked fish may have not have survived there. Biological assessment of the bass populations revealed that the fish inhabiting the SIRC Lakes were not as healthy as the populations inhabiting Middle Basin and Duralia Lake or as healthy as a population previously studied in its native habitat in the adjacent Hawkesbury-Nepean River.
Recommendations were made in relation to monitoring and improving lake water quality and reducing the potential impacts by eastern gambusia and common carp on the health and aquatic biota of the Penrith Lakes. The bass stocking data should also be assessed and the bass biological study expanded to provide insights into ways of optimising the stocking program. The adopted fish community sampling protocol should be continued in its current form as it appeared to provide a representative insight into the status of the aquatic communities inhabiting the Penrith Lakes.