Asian Carp Could Claim One-Third of Lake Erie Biomass

An Illinois fisheries biologist holds a bighead carp, one of the Asian carp species that threatens to invade the Great Lakes. Illinois Department of Natural Resources

If invasive Asian carp make it into Lake Erie, their populations could grow large enough that the animals would make up one-third of the lake's quantity of fish, according to new research.

The fish, belonging to a species native to East Asia, have been spreading throughout the Mississippi River basin for the past few decades, and many fear that they will soon make their way into the Great Lakes—and some think it's only a matter of time, given that their range has expanded to be quite close to several of the lakes.

In a study published December 30 in the journal Transactions of the American Fisheries Society, scientists calculated that an Asian carp invasion of Lake Erie would significantly harm several economically important species, particularly rainbow smelt and walleye, which are both fished at a commercial level. In the case of such an invasion, gizzard shad, another important species, would decline by 37 percent, while populations of rainbow and lake trout would also dip, says study co-author Edward Rutherford, a researcher with the Great Lakes Environmental Research Laboratory.

Some fish species, however, would actually stand to gain from the invasion. Populations of smallmouth bass would increase by a projected 16 percent, says Hongyan Zhang, the study's first author and a research scientist at the University of Michigan.

While the effect would be quite significant, the carp aren't likely to dominate Lake Erie as powerfully as they do parts of the Mississippi and Illinois Rivers, where they can account for 80 to 90 percent of the biomass, Rutherford says. This has caused major problems, including reducing populations of native fish.

Bill Pine, a researcher at the University of Florida who wasn't involved in the paper, says that the potential impacts of an Asian carp invasion don't appear to be as great as many feared. Some worried, for example, that the carp might reach the high levels seen in the Illinois River, but this paper shows that wouldn't happen even in a worst-case scenario, Pine adds.

The team is working to translate their model, which analyzes the lake's food web, into an economic one. That could help answer questions like whether the economic impact of a Lake Erie carp occupation will exceed the costs of keeping the carp out. The local government already has taken measures to stop the invasion, including engineering projects and public information campaigns.

The researchers think the impact of an invasion would exceed the costs of preventing one, especially if the ecological damages are taken into account, Rutherford says. (But their final calculations aren't yet complete.)

The team expects impacts on other Great Lakes would be similar, or perhaps less significant, as Asian carp do best in areas with a lot of plankton, their food source—and Lake Erie generally has higher concentrations of plankton than the other Great Lakes do.