A highly threatened fish, that grows no more than 8 centimetres in length, is returning to the Lower Murray in numbers not seen since the Millennium Drought.
The successful return of the Southern Pygmy Perch is being attributed to a combination of adequate river flows, careful water level management and healthy wetland habitats.
The Southern Pygmy Perch is a small fish that occupies the fringing wetlands of Lake Alexandrina in the Lower Murray. The health of these wetlands is highly dependent on careful management of water levels controlled by operating gates at 5 barrages, which also stop sea water entering the lakes from the Coorong.
Southern Pygmy Perch disappeared from the Lower Lakes in 2008 during the Millennium Drought, but thanks to carefully planned reintroductions coordinated by the Molecular Ecology Lab at Flinders University along with other organisations, informed lake level management, and delivery of water for the environment, populations of this threatened fish are now improving.
Project Officer, Coorong, Lower Lakes and Murray Mouth for the Department for Environment and Water (DEW) Kirsty Wedge said monitoring undertaken as part of Murray-Darling Basin Authority’s ‘The Living Murray program’ recorded high numbers of Southern Pygmy Perch in the March 2022 survey – the highest of any year since the Millennium Drought.
“This was enhanced by increased River Murray flows, combined with delivery of water for the environment, which increased water levels in the Lower Lakes, extending the fish breeding season,” Ms Wedge said.
Fish ecologist from the University of Adelaide Dr Scotte Wedderburn, said this positive outcome is despite an increase in the introduced predatory Redfin Perch over the same period.
“The combination of adequate river flows, careful water level management and healthy wetland habitats appears to minimise the impacts of Redfin Perch on the Southern Pygmy Perch population.
“It’s been a long time since we’ve seen an extended period of good flows like this through spring and summer, and great to see threatened fish like the Southern Pygmy Perch respond well through breeding and successful recruitment,” Dr Wedderburn said.
The Ngarrindjeri Aboriginal Corporation (NAC) was also involved in this project through hands-on field monitoring and DEW provided funding and project management support.
Yarluwar-Ruwe Project Coordinator for the NAC Rick Hartman said it is so beneficial to have Ngarrindjeri community on country, learning new skills, sharing cultural knowledge and helping to protect native fish in their local environment.
“It is part of Ngarrindjeri culture to be as one with nature and protect all living things,” Mr Hartman said.
DEW is committed to protecting South Australia’s River Murray wetlands and works with partner agencies such as SA Water, the Murraylands and Riverland Landscape Board, the Commonwealth Environmental Water Office and the Murray-Darling Basin Authority to deliver water for the environment in conjunction with natural river flows.
Monitoring associated with this project was delivered by The Living Murray, a joint initiative funded by the New South Wales, Victorian, South Australian and Australian Governments, coordinated by the Murray–Darling Basin Authority.
You can find more information about water for the environment on the DEW website – Department for Environment and Water - Water for the environment