Corn Fed Cobia?

Scientists discover key to easing aquaculture’s reliance on wild-caught fish

By Chris Landers

Photo of Dr. Allen Place and Dr. Aaron Watson holding cobia food
Researchers are making cobia go vegetarian. Pictured: Dr. Allen Place (left) and Dr. Aaron Watson (right). (Univ. of Maryland Center For Environmental Science photo)

Farm-raised fish and shellfish account for nearly half the world's seafood supply, but when the fish being raised are carnivores, that can be a problem. Fish like cobia, which eat squid and other fish in the wild, need a similar diet in the tank — fish meal and fish oil — and it can take five pounds of wild fish to produce one pound of farmed fish. That diet might work for the cobia, but it's tough on the farmers' pocketbooks, not to mention its effect on baitfish stocks.

Scientists at the University of Maryland's Center for Environmental Science have hit on a possible solution — make the cobia go vegetarian. To try it in the lab, they replaced the fishmeal with a mixture of corn, wheat, and soy; and soybean or canola oil stand in for the fish oil.

To that they added taurine, an amino acid found in carnivorous fish — and in energy drinks, by the way. Their research found that cobia were able to grow to maturity on this vegetarian diet.

"This makes aquaculture completely sustainable," said study author Allen Place. "We can now sustain a good protein source without harvesting fish to feed fish."

In addition to the potential to turn aquaculture into a more profitable enterprise and ease the pressure on catching wild fish, raising fish on a vegetarian diet also means cleaner fish to eat, with levels of PCBs and mercury as much as 100-fold lower.

“Right now, you are only supposed to eat striped bass once every two weeks,” said Place.  “You can eat aquaculture-raised fish twice a week because levels are so low.”