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River Prawn Stock Enhancement Underway

Swan River Prawn Restock
Swan River Trust Principal Scientist Kerry Trayler, recreational fisherman Will Smithwick, Challenger Institute of Technology Aquaculture Research and Development director Greg Jenkins, Challenger researcher Robert Michael and recreational fisherman Kevin Reid celebrate the release of the first Western School Prawns into the Swan River.

Scientists  are celebrating a world first after successfully culturing Western School Prawns. 

The breakthrough achieved by project partners the Swan River Trust, Challenger Institute of Technology, Murdoch University, Recfishwest, WA Fish Foundation and the Department of Fisheries could signal a welcome return to recreational prawning in the Swan Canning Riverpark. 

Swan River Trust Principal Scientist Dr Kerry Trayler said culturing the Western School Prawn (Metepeneus dalli) was the first step in the restocking program and researchers believe large numbers of juvenile river prawns could be released into the Riverpark in April 2014.

“This is the first time Western School Prawns have been cultured anywhere in the world and we have learnt a lot along the way,” she said.

“The road to successfully culturing Western School Prawns has been difficult and the Challenger Institute research team had to overcome major hurdles including sourcing gravid prawn brood stock in a narrow time frame and working with tiny river prawn larvae.

“Once females were collected, they were kept in tanks and allowed to spawn naturally and the hatched larvae were grown out to the size where they were ready to bury into the riverbed.

“It takes about a month to grow the prawns to a stage where they can be released. Once they can bury themselves in the shallows of the river they are less vulnerable to a range of pressures.”

Dr Trayler said the Western School Prawns are comparatively small and their tiny juveniles were more difficult to culture than other prawn species. Researchers had to experiment to find the right conditions and diet to raise the juveniles.

Swan River Trust Prawn Restock

“The river prawns were fed a special algae paste and subjected to a variety of temperatures and other controls to determine ideal culturing conditions,” she said. 

“The next important phase will be to up-scale the culturing process and build in a monitoring and research framework for identifying the key environmental factors that impact on Perth’s river prawns.”

Dr Trayler said historically fishing pressure and environmental change had been blamed for the river prawns decline and scientists were keen to determine what was limiting the prawns’ natural recruitment.

“We hope to answer a question that has baffled West Australians for more than 20 years and discover the key to river prawn survival and growth for future generations of fishers,” she said.

“At this stage it is difficult to predict how abundant Western School Prawns might become as that is dependent on a range of environmental factors.

“The river prawn restocking will need to be sufficient to overcome both predatory and environmental pressures before we will see a significant improvement and we are aiming to get a better understanding of those variables as part of this project.”