ST. PAUL, Minn. -- In some Minnesota lakes, invasive species are limiting the growth of a popular fish, according to a new study of the effects on walleye.
University of Minnesota researchers say the culprits are zebra mussels and spiny waterflea. They found in lakes where these are present, they can reduce the growth size of walleye from 12% to 14%. The species take away zooplankton, a food source for the fish.
Jeff Forester, executive director of the group Minnesota Lakes and Rivers Advocates, said the findings should spur stronger action by the state to prevent the spread of these species.
"What we've been doing -- this kind of emphasis on education and personal responsibility -- that's not getting it done," he said. "I think it's slowed the spread, but it certainly hasn't stopped it."
Forester said he'd like to see the state adopt more stringent boat-inspection policies, such as making it a requirement for people getting an operator's license. The Department of Natural Resources said that, in coordination with local governments, it conducted more than 500,000 watercraft inspections last year, a record number.
Walleye is a favorite fish for anglers and many resorts rely on its popularity for business. Forester acknowledged that it's a difficult balance for the state because boats are helping to spread these species, but many lake communities are dependent on water recreation.
"How do we use the lakes in such a way that they're protected for the future," he said, "and we're protecting the resource, which is not the lake itself, but the quality of life and the economics."
One of the lakes in the study, Mille Lacs Lake, has seen many controversies surrounding walleye fishing in recent years. The DNR has enforced strong limits for anglers so the walleye population can rebound. Some of those restrictions have been slowly lifted as walleye makes a comeback in the popular lake.
The study is online at springer.com.
