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| Southern bluefin tuna in a marine farm off Pt Lincoln. Photo by Adam Watkins |
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| Researcher Quinn Fitzgibbon about to release a live tuna into the waterbed. |
The findings have been made by Earth & Environmental Sciences PhD student Quinn Fitzgibbon and colleagues, in a study where they monitored live tuna swimming inside a 350-tonne "waterbed".
The research team also found that tuna use twice as much energy processing their food as any other fish, and so need to eat more to grow.
"Because of their high oxygen and energy demands, we think of tuna as the V8 race car of the fish community," Mr Fitzgibbon says. "Their large, finely tuned mechanisms support great performance, but use a lot of fuel and are expensive to run."
While tuna farming has quickly grown to be Australia's most valuable aquaculture industry - worth about $300 million annually, mostly supplying the international sashimi market - until now little has been known about these large, strong fish because of the difficulties of studying them.
The information the research team is collecting is being used in models that describe the energy needs of growing tuna. It will also help tuna farm managers ensure the health of their fish and assist in the design of feeding strategies, helping to maximize productivity and profitability.
By installing a sealed bag or waterbed made from reinforced plastic into an ocean tuna farm, Mr Fitzgibbon was able to measure the consumption of oxygen of the tuna inside.
Tuna are introduced to the waterbed through a sealable port and can spend weeks inside, happily swimming around and feeding. The bag has probes to measure oxygen levels in the water, video cameras to record the tuna's behaviour, and lights that turn on at night so filming need never stop.
This innovative four-year research project has "opened a window on the unique physiology and ecology of this fascinating fish", Mr Fitzgibbon says. Mr Fitzgibbon has been working with scientists from South Australian Research and Development Institute (SARDI) Aquatic Sciences, and his work has been supported by the Aquafin CRC and its participants, including the Tuna Boat Owners Association of South Australia, the SA Government and Fisheries R&D Corporation.
Quinn Fitzgibbon is one of 16 young scientists presenting their research to the public for the first time thanks to Fresh Science, a national program sponsored by the Federal and Victorian Governments. The program identifies new and interesting research being done by early-career scientists around the country.
Of the 16 Fresh Scientists selected for 2007 from more than 80 nominations, four are from the University of Adelaide. The others are Cadence Minge, Martin Sale and Edwina Sutton.