Asian carp have yet to establish a presence in the Great Lakes, but scientists have already begun researching the possible effects of an invasion by the non-native species.

In a study recently published in the journal Transactions of the American Fisheries Society, researchers from the National Oceanic and Atmospheric Administration (NOAA) and the University of Michigan state that if Asian carp get into Lake Erie, the fish could eventually account for about a third of the total weight of fish in the lake. This means that plenty of native fish, such as the lakes’ prized walleye and rainbow trout, will see their populations cut significantly.

“This study goes beyond previous efforts in two significant ways. It focuses on the food webs and—where model input data were not available—it includes uncertainty estimates from experts,” co-author Ed Rutherford, a fisheries biologist with the NOAA, said in a press release from the University of Michigan.

Previous studies’ findings have varied widely on how Asian carp could affect the Great Lakes. Many researchers fear that if the fish get into the Great Lakes, the impact on sport fish species could be devastating. Others, however, point out that the Great Lakes are not ideal habitat for carp and that the fish may have less success than expected. The new study indicates that the carp will have a more moderate effect—but still a very noticeable one.

According to the study, species such as walleye, rainbow trout, gizzard shad, and emerald shiner will all see significant declines. The greatest impact will be felt by the emerald shiner, which researchers predict to decline by up to 37 percent should Asian carp reach Lake Erie. Other fish species, such as smallmouth bass, may see their populations go up as a result of weakening competition from native predators and the abundance of food provided by juvenile Asian carp. Overall, researchers said that Asian carp could eventually take up 34 percent of the total biomass in Lake Erie.

While that number may be startling to some, it pales in comparison to some parts of the Mississippi River, where Asian carp now account for up to 90 percent of all fish biomass. Still, conservationists say the thought of Asian carp in Lake Erie is frightening.

“It’s very sobering,” Marc Gaden, a spokesman for the Great Lakes Fishery Commission, told the Associated Press. “Lake Erie is one of the most productive inland fisheries in the world. It wouldn’t be as valuable by any stretch of the imagination if one out of every three pounds of fish were Asian carp.”

The two Asian carp species that biologists are most worried about are bighead and silver carp, both of which can grow up to immense sizes and can be difficult to catch with traditional fishing. Asian carp are considered a threat because they nip away at the food chain by its very foundations: plankton. Carp can put a big dent on plankton, which in turn will send out a ripple effect across the food chain and threaten a $7 billion sport fishing industry in the Great Lakes.

Thankfully, the carp have not breached the barriers into the largest group of freshwater lakes in the world. A series of man-made barriers in the Chicago Area Waterways System has so far been successful to halting the Asian carp’s advance, and additional—but very expensive—plans are also under consideration to prevent the carp from reaching the Great Lakes.

Image from David Ostendorf/Missouri Department of Conservation

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