The (partial) return of threatened freshwater fish to Lower Lakes

The (partial) return of threatened freshwater fish to Lower Lakes

Dramatic water level recession and habitat degradation (e.g. elevated salinity, loss of submerged vegetation) placed several species of threatened freshwater fish under risk of extirpation in the Lower Lakes of the Murray. In response, wide-ranging actions (many previously by Michael Hammer of Aquasave – NGT) – removing individuals from the wild; captive maintenance and breeding; and the establishment of refuge dams – were carried out to maintain fish until favourable conditions returned and fish could be re-introduced. In 2010/2011, broad-scale rainfall and significant inflows in the Murray-Darling Basin impr0ved flow and habitat availability around the Lower Lakes.

Sampling SPP release site on Hindmarsh Island

Since 2011, two rounds of re-introductions of Yarra Pygmy Perch, Southern Pygmy Perch, Murray Hardyhead and Southern Purple-spotted Gudgeon have returned over 10,000 fish to lower lakes through a colloboration between Aquasave – NGT and SARDI (Chris Bice) as part of the Critical Fish Project Critical Fish Project funded by the CLLMM group of DEWNR.

Chris Bice and I have been conducting fish monitoring around the Lower Lakes in recent weeks to assess the post-introduction success and sites for an upcoming round of reintroductions. To date, we detected low numbers of all four species (although collected Murray Hardyhead appear to be wild fish not reintroduced fish) at six of the reintroduction sites across the recent monitoring (and similar monitoring conducted in Autumn 2012). Encouragingly, recently collected Yarra Pygmy Perch represent the first of the species observed in the region since 2008 and new Southern Pygmy Perch recruits (i.e. individuals that were most likely spawned by the individuals we released) were also detected. These outcomes indicate the reintroduced fish are persisting (and most likely reproducing and recruiting), and we look forward to another round of reintroductions and detection of larger populations in subsequent monitoring.

First YPP sampled around lower lakes since 2008

For more information on the first two rounds of reintroduction, see a copy of Bice et al. (2012) here.







Nick Whiterod