Aquaculture for all

Science Aims to Understand Invaders

SOUTH AUSTRALIA - Uncontrolled pest fish populations are potentially damaging to the fishing industry. Tilapia and other pest fish species compete with native fish such as barramundi, and can damage ecologically sensitive wetlands.

And the recent discovery of tilapia in the Gulf of Carpentaria catchment highlights the need for scientific research on control strategies for pest fish, says the Department of Primary Industries and Fisheries (DPI&F).

Now, in partnership with the Invasive Animals Co-operative Research Centre, DPI&F is undertaking an ambitious project to learn more about the biology of tilapia populations in North Queensland.

The project will model the effects of various potential control strategies available now or in the future to assess their effectiveness.

DPI&F principal fisheries biologist John Russell, who is based in Cairns, said this was the most far reaching investigation of tilapia biology ever undertaken in Australia.

"We hope our findings will help us better advise the community on the best means of controlling this pest species," Mr Russell said.

"We already know a lot about the secret life of tilapia in Australia. So far we have collected information on the reproductive capabilities, spawning season, ages, numbers and sizes of more than 5500 fish in the Cairns and Tableland area.

"What many people don't realise is we actually have two species present in the Cairns area - the Mozambique mouth breeder and the black mangrove cichlid.

"Both of these are extremely hardy and capable of dominating the fish fauna in dams, creeks and rivers".

Serious Problem

Mr Russell said fishers in the lower reaches of the Mulgrave River in Far North Queensland, where tilapia were well established, would appreciate the seriousness of the problem.

"The thousands of fish that were caught in the community-run 'Tilapia Terminators' competition last year is evidence of how plentiful they have become," he said. "Causes of this include a lengthy breeding season and parental care of their young which maximises survival of eggs and larvae at a time when they are most vulnerable to predators."

The female Mozambique mouth breeder protects eggs and larvae by keeping them in their mouths until they are old enough to compete effectively in the wild.

"They can live for up to eight years or more and start breeding at an early age. Given this powerful reproductive capability and their ability to adapt to and live in a range of habitats it is not difficult to see how they can quickly colonise new areas.

"We hope our research into control activities will help in preventing future populations being established."

DPI&F is currently undertaking control activities, mainly through electro-fishing, and is also stepping up surveillance in both the Cooktown area and the Gulf to track the extent of any infestation.

An education campaign has also been running throughout north Queensland during the past 12 months. A range of identification materials and advice on how to deal with pest fish is available.

For more information visit: www.DPI&F
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