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Young researcher gives crayfish industry some good news

September 08, 2006

KWillows.thumb.jpgExperiments conducted by a young researcher from The University of New England have produced results that could help to boost production in Australia's freshwater crayfish industry.

Honours student Karen Willows (pictured here) has shown that rearing yabbies in outdoor ponds or dams has better outcomes than keeping them in temperature-controlled indoor aquaria. Most significantly, the yabbies kept outside grew faster than those kept in the indoor tanks.

She has also shown that yabbies grow just as quickly on a diet of 20 per cent protein as they do on a more expensive diet of 30 per cent protein.

"Both of these results were rather unexpected," Ms Willows said. "We thought there would be quicker growth in the temperature-controlled environment (a constant 25 degrees) and with the more protein-rich diet. Our preconceptions reflected some of the current thinking within the industry itself." She believes that her results could help pave the way to a cost-effective and productive future for a fledgling Australian industry with great potential.

Ms Willows undertook the research as a Bachelor of Science (Honours) project, supervised by UNE Senior Lecturer Dr Ian Godwin. She monitored the growth of 196 juvenile yabbies (Cherax destructor), reared under differing experimental conditions, over a period of two months. She bred the yabbies and conducted the experiments at CSIRO Livestock Industries' F.D. McMaster Laboratory near Armidale, where a yabby breeding program has produced a faster-growing strain. The Laboratory's Officer-in-Charge, Dr Ian Purvis, co-supervised her work. "To monitor the yabbies in the pond, I had to row out in a kayak," Ms Willows said. "They were kept in cages - the same as the ones in the indoor aquaria - and at a depth of 90 cm."

Her experimental procedures and conclusions so impressed the 80 delegates at an international "astacology" (freshwater crayfish culture) conference in Queensland last month that they voted her paper the "best student presentation". Her findings are being published in the Proceedings of the conference - the 16th Biennial Symposium of the International Association of Astacology - and she is hoping for an even wider audience through publication in a leading aquaculture journal. A paper by another yabby researcher at UNE, PhD student Rod Duffy, was voted one of the four best presentations at the conference.

Ms Willows pointed out that there are 120 known species of freshwater crayfish in Australia, and more are still being discovered. "The industry - although small - is growing," she said. "However, a lot more research needs to be done. Our present knowledge of nutrition is not sufficient to support an intensive hatchery system."

Her own discoveries have added to that knowledge, showing that a diet lower in protein than the currently recommended 25 per cent is sufficient for optimum growth. Also, being kept in outdoor ponds gives the crayfish access to water-borne organisms that supplement their diet and boost their growth. This - and other benefits of more natural living conditions - contributed to the fact that there were only half as many deaths among the outdoor yabbies as among their aquarium-raised counterparts.

"I hope these findings will be of use to an Australian industry that - judging from the reports of overseas delegates to the conference - has enormous potential," she said.

For more information, contact Karen Willows on 0413 515 214.

Posted by Jim Scanlan at September 8, 2006 03:52 PM