Tuna grow faster in deep seas: research

15 Oct 2012, 3:22 pm   -   Source: AAP

In an important development for the fish industry, Australian researchers have shown Tuna grow faster in deep sea "farms".

Deep sea tuna farming could be the way of the future, after Australian researchers found the fish grow twice as fast when raised in "farms" further from the coast.

University of Tasmania scientist Nicole Kirchhoff said the research could open the way for commercial fisheries around the world to find financial backing for deep sea "farms", after previously struggling to get funding to relocate, due to a lack of research about outcomes.

The University of Tasmania research was funded jointly by the Australian Southern Bluefin Tuna Industry Association and the Fisheries Research and Development Corporation.

It tracked the health and growth of about 10,000 tuna caught and raised for sale in caged farms the traditional 20km offshore, compared with about 10,000 others raised in farms 50-60km offshore.

"We found that when we moved the fish (further) offshore they got to market size in about half the time as the fish in the traditional environment," Dr Kirchhoff told AAP.

"We also found none of the parasites we commonly find in ranch-farmed tuna and ... what we had to feed them to get to market weight was a lot less."

Ranch-farmed tuna are caught weighing between 15-20kg and are fed pilchards while caged until they grow to more than 30kg for harvest.

Dr Kirchoff said the world-first research found the tuna farmed further offshore reached 30kg or more in six weeks, compared to 13 weeks for those closer to shore, were happier and healthier on 15 different markers and ate less, making deep-sea farming more sustainable.

The research was conducted at tuna farms in Port Lincoln, South Australia, from January to September 2010 and was presented at a Fresh Science event in Melbourne on Monday.

Dr Kirchhoff said four of the 12 Port Lincoln tuna farms had now moved further offshore and organisations around the world were interested in the research results.

She said possible reasons for tuna growing faster when caged further offshore could include more stable water temperatures, clearer, cleaner waters allowing the tuna to see their prey more clearly and greater water depths making them less vulnerable to ocean-floor parasites.

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