Grow Fish

If wild fish turn unhealthy, can farmed stocks swim to the rescue?

WITH MANY WILD FISH STOCKS in decline from overfishing and other threats, aquaculture—the managed cultivation of fish—has taken on a larger role in feeding the nation’s growing appetite for seafood. But are farmed fish really any freer from contamination than wild ones?

That all depends, says Jeff Malison, director of the CALS aquaculture program in the Department of Animal Sciences.

“No fish is going to be pollutant-free,” he says. “But yes, farmed fish can have much lower levels (of contaminants) than wild fish—at least they have that potential.”

Because farmed fish accumulate toxins from the environment and their food just like wild fish do, the key to producing a “clean animal” is to grow it in fresh, unpolluted water and feed it a diet free of toxic ingredients, Malison says. But farmed fish also have a fin up on their wild kin: They grow much faster, which means they have considerably less time to collect pollutants during their short lives. Pond-raised rainbow trout, for example, are usually big enough for the dinner plate by one year old, whereas wild trout of the same size might be three to four years old.

Wisconsin happens to be among the top 10 producers of farmed rainbow trout in the country. But before consumers rush out to buy farm-raised filets of other popular Midwest fish, such as yellow perch and walleye, they should know that fish farming is hardly routine. Malison points out that we raise only about six to 10 bird and mammal species for meat, but we eat around 200 species of fish, each with its own set of environmental needs and tolerances. And with the exception of a few species, most fish have yet to be bred for captivity.
“Even though it was practiced in China 4,000 to 5,000 years ago,” says Malison, “aquaculture is still relatively young as a technological industry.”

The aquaculture program has been working since the 1970s to improve two critical factors that limit the production of fish: reproduction in captivity and the costs of raising juveniles. The diminutive yellow perch is a prime example. Because it takes many perch to make a meal, farmers need to grow lots of them. “And when you need lots of them you’ve got to make sure the cost of the babies is really, really low to develop a profitable industry,” says Malison. “So we’ve been doing a lot of research on reproduction to try to reduce the cost of fingerling production.”

CALS researchers have also studied walleye, but for a very different reason. Carnivorous and aggressive, “it’s really kind of a rascal in captivity,” Malison says, noting that farmed walleye have a tendency to attack their own mates. To solve this problem, his group is now using Wisconsin Department of Agriculture, Trade and Consumer Protection funds to breed the brutish walleye with a closely related fish, called the sauger. The result is a much more docile fish that also grows faster.

The success of these projects will surely expand the choices consumers have at the grocery store. But another goal is to expand the state’s aquaculture industry, which also encompasses bait fish and fish for stocking lakes and rivers. And as Malison notes, Wisconsin has plenty to bring to the table—water resources, farming expertise and, of course, the market. Fish fry, anyone?

Tags: , , , ,
Posted in Environment, Featured, Food, Health, Summer 2010 |