Invasive Asian carp, steadily moving northward for decades, could eventually make up a third of the fish weight in Lake Erie if they successfully invade and become established there, researchers say.

Voraciously consuming plants and animals that serve as food for native species as they work their way north through the Mississippi River system, the Asian carp could cause many Lake Erie native fish species to go into decline, including important commercial and sport species like walleye and rainbow trout, scientists say.

That's one finding of a study by University of Michigan researchers, working with colleagues at other research institutions in America and Canada.

They used a computer model to predict the likely impact on food webs if silver and bighead varieties of Asian carp gain a foothold in Lake Erie, they report in the journal Transactions of the American Fisheries Society.

While some native species like walleye and trout would suffer as the carp out-compete them for food, some other fish-eating species, such as smallmouth bass, might benefit from an abundance of juvenile carp as a new food source, the researchers suggest.

Still, Asian carp could eventually account for up to 34 percent of the lake's total fish weight, says UM researcher Hongyan Zhang.

"Fortunately, the percentage would not be as high as it is today in the Illinois River, where Asian carp have caused large changes in the ecosystem and have affected human use of the river," she says.

Experts have differed in their predictions of what impacts Asian carp could have on the Great Lakes; some believe the carp may decimate fisheries and lake food webs, while other researchers suggest the Great Lakes are not suitable carp habitat and the effects of their presence would be minor.

The new study falls somewhere in between in its suggestions, the researchers say.

Asian carp have established themselves in watersheds adjacent to the Great Lakes but have not been found in the lakes themselves yet, which makes the study's predictions subject to modification, they say.

"We don't know how these two Asian carp species are going to do in Lake Erie, so we have to incorporate that uncertainty into our model projections," says study co-author Doran Mason, an ecologist at the Great Lakes Environmental Research Laboratory.

"It's like using computer models to predict a hurricane's path and intensity and including the margin of error in the forecast."

The researchers are also conducting modeling studies on possible carp impacts on other Great Lakes, including Michigan, Huron and Ontario.

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