The additive Brown is currently testing is a type of omega-6 fatty acid called conjugated linoleic acid (CLA), which researchers believe could be an effective weapon against cancers and diabetes.

"We found that by adding CLA to fishes' diets we can get more of these fatty acids into the fishes' tissues than is found in any other animal," said Brown, a nutritional aquaculturalist. "Meat and milk from ruminant animals are good sources of CLA, but these fish retain even higher levels."

Purdue scientists discovered that some fish stay lean while others become much fatter because they retain the lipids, or polyunsaturated fat, from the fatty acids. Two fish models they studied have very different activity and metabolism levels, and differ in the amount of fat they retain. Eating a high fatty acid diet in a farm environment turns hybrid striped bass into 'little butterballs', while yellow perch stay very lean, Brown said.

The ability to raise more nutritional fish of a variety of species should encourage growth of the aquaculture (fish farm) industry, he said. But fish are the last major food item still obtained primarily from the wild.

"The wild fish supply just isn't sufficient to provide us with the amount necessary for human consumption," added Brown. "We have to develop new aquaculture production that rivals global production of soybeans, pigs and chickens if we want to keep eating fish and shellfish."

Since 1985, commercial fishing has annually produced approximately 90 million metric tons (mmt). In contrast, aquaculture production has doubled every decade since 1970. Figures from 1999 show annual aquaculture production at 42 mmt.

Worldwide production of hogs is approximately 83 mmt yearly and that of chickens is 46 mmt, according to 1995 figures. Brown estimates that to keep up with demand, annual aquaculture production must increase by 40 mmt to as much as 100 mmt by 2035.