By Dave Cohen
1 July 2013
(Decline of Empire) – Few stories better capture the human relationship with the natural world than Science Daily's Developing Techniques for Tuna Aquaculture (12 June 2013).
Swimming around and around in a 20,000 gallon tank at the University of Rhode Island's Bay Campus are several large yellowfin tuna captured last fall about 100 miles off the Rhode Island coast. The fish are part of the first effort in the United States to breed tuna in a land-based aquaculture facility to meet the growing demand for one of the ocean's top predators.
"Worldwide demand for tuna increases yearly, even as tuna stocks are dwindling precipitously," said Terry Bradley, a URI professor of fisheries and aquaculture. "What we're trying to do is produce fish in captivity and take the pressure off the wild stocks."
Bradley and Peter Mottur, director of Rhode Island-based Greenfins, are taking the first steps in developing the techniques to raise tuna from egg to harvest size while creating a new sustainable industry in Rhode Island.
According to Bradley, some in Australia, Mexico and several Mediterranean countries are doing what he calls "tuna ranching" by capturing wild tuna, putting them in pens and raising them to harvest size.
"All they're doing is taking wild fish and fattening them up," he said. "It's still depleting the wild population and has had a long-term impact on tuna stocks."
Endangered bluefin and yellowfin tuna are large predators which range far and wide in the world's oceans. A 20,000 gallon tank?
Bradley and Mottur are starting the process by trying to get a few wild-caught tuna to spawn in the URI tank, but it is a challenging undertaking. Tuna are long-distance migrants that swim at great speeds, so acclimating them to a 20-foot diameter tank has been difficult. Once the fish spawn and the eggs hatch, the microscopic larvae must be fed live food raised on site. Then they must be weaned from live food to a dry, formulated feed.
Bradley and Mottur believe that construction of a larger tank, which will be built at the URI Bay Campus later this year, will markedly increase the project's likelihood of success.
"Tuna are open ocean fish that require a lot of space and need very good water quality," Bradley said. "If you put too many fish in a tank, they get stressed and the water quality begins to degrade. The less you stress them, the more likely they are to spawn in a reasonable time frame."
Yes, that's the ticket—build a larger tank! How big should that tank be? I think something the size of Rhode Island itself would do very nicely.
Let us move beyond the absurdity of raising tuna in a tank. How does this project reflect the human relationship with the natural world? [more]