Asian Carp Soon To Be Seal Food

A fish that’s becoming a growing problem in Midwest rivers might end up being fed to sea lions and penguins in zoos if a pilot project successfully develops.

Courtesy photo
Silver carp jump into the air as a U.S. Geological Survey research boat passes by in this University of Missouri photo. A pilot project would turn nuisance Asian carp into food for zoo animals.

Researchers for the University of Missouri-Columbia, the federal government and the Saint Louis Zoo are collaborating on a plan to create a market for two troublesome Asian species: the silver carp and the bighead carp.

Both species seem to be taking over the Mississippi, Missouri and Illinois rivers. Silver carp are particularly hazardous because they’ve been known to leap out of the water and land in boats.

"These are powerful, powerful fish," said Rob Hayward, an MU fish researcher. "A 25-pound fish jumping 8 feet out of the water and landing in a boat creates quite a hazard."

Work is under way to develop fish patties made of ground up Asian carp that can be served as food to captive zoo animals. If the commercial market develops, it could provide multiple conservation benefits.

One dividend would be a reduction in the number of the troublesome fish in the rivers. The other benefit is the reduction in fishing pressure on species such as herring and mackerel, which are now fed at zoos at a cost of 30 to 70 cents per pound.

Ellen Dierenfeld, a fish nutritionist at the Saint Louis Zoo, said the carp food source could be modified to provide for additional fat content and nutrient quantity. Questions still abound about texture and whether the fish food will stick together when the trainer tosses a morsel to a sea lion for positive reinforcement. "We’ve done the toss test of a cake," Dierenfeld said today. "A couple of interns have thrown them back and forth to make sure they hold together and to make sure the texture is right.

"The animal palate will be the trickiest," Dierenfeld added. "We can make the most nutritious diet, but the animal may not like it."

With humans in the United States, that’s certainly a problem. Hayward said the Asian carp is in high demand on dinner tables in Asia and Europe. If Americans craved the fish the way others around the world do, there wouldn’t be a population problem in U.S. rivers. "This is the most commonly consumed fish worldwide," Hayward said. "We are the oddballs."

The Asia carp species were first noticed in 1993. No one knows how they got into the rivers, but some suspect that they might have escaped an impoundment in the south during the great floods that year.

Duane Chapman, a research fish biologist with the U.S. Geological Survey, said the Asian carp feed on tiny fish and plant organisms that are food sources for small fry of native species. Chapman said while it’s difficult to measure the carps’ impact, a recent natural survey in Illinois found that samples of bigmouth buffalo and gizzard shad were smaller than in the past - an indication that they are growing more slowly than before.

At the same time, Chapman said Asian carp grow quickly, making it difficult for them to be prey for predators such as walleye and flathead catfish.

Hazard, Chapman and Dierenfeld hope the project will create a market that will make it worthwhile for commercial fishers to collect the Asian species with nets.

"We hope to have a product ready to test with animals that’s nutritionally complete in the spring," Dierenfeld said. "Now, if the fish eaters will just bite into it."