Impact of Asian carp on Great Lakes could be overestimated

Thursday, January 7, 2016 - 6:04pm

For many years, experts have investigated the effects of invasive species on the Great Lakes. However, using a new computer model, University researchers have discovered new information that shows the impact of Asian Carp in Lake Erie could have previously been overestimated.  

According to the new findings, a few species of fish would see a population increase in response to the influx of Asian carp, including smallmouth bass. Others could see a decrease of up to 37 percent, which is lower than the decrease in native fish population that some experts have previously predicted.

The new study, conducted by Hongyan Zhang, assistant research scientist at the School of Natural Resources and Environment, along with professors from other universities across the nation, primarily focused on aiding water quality management in the Great Lakes. The team also included researchers from the U.S. Forest Service, Fisheries and Oceans Canada and the Ontario Ministry of Natural Resources and Forestry.

The plankton-eating Asian carp are not currently present in Lake Erie, though they are established in watersheds near the Great Lakes, creating interest for such research.

“We found that the Asian carp, if they come into the Great Lakes, into Lake Erie, they could be very abundant,” Zhang said. “They could become one-third of the total fish weight. That is quite a lot.”

If they were to successfully invade Lake Erie, Asian carp would likely affect the food web in two regards: The carp would likely compete with native fish by eating plankton, the food source for both native fish and the carp, and native fish could potentially feed on younger Asian carp if they became a part of the lake’s ecosystem.

Scientific predictions of the impact of Asian carp on the Great Lakes differ. Some experts say they would decimate the fish populations and food webs, similar to their effect on the Illinois River, where Asian carp have become a large part of the ecosystem.  

Other experts argue that the Great Lakes are an unsuitable habitat for Asian carp, so the effects of introducing the fish would be minimal. This new study falls in between these two predictions.

“Compared to what happened in the Illinois River, where more than 80 percent of the fish is Asian carp in that area, the percentage is not very high for Lake Erie,” Zhang said. “But it is a big lake, and it has a lot of fish, more than the other Great Lakes, and if one-third of the fish population will be Asian carp, that is very abundant. The impact on the population is to decrease most of the fish species. That is not a good thing.”

This project is the first to use a food-web model to examine the effects of Asian carp in Lake Erie. The team of researchers interviewed 11 experts on Asian carp and Great Lakes ecology. They then incorporated their predictions into a computerized model projecting the effect of the Asian carp. The experts were then asked to indicate their level of uncertainty with each statement they provided, and this was included in the model as a margin of error.

Ed Rutherford, a co-author of the study and a research fishery biologist at the NOAA Great Lakes Environmental Research Laboratory, said the unique methodology of their research was instrumental in addressing the issue.

“What was interesting to me was that with our model, we were able to put numbers to the estimates about the impact of Asian carp,” Rutherford said. “So we were able to fill in knowledge gaps of exactly what would happen if Asian carp is introduced to the Great Lakes.”

Overall, the increase in species could be minimal, Rutherford said. In terms of a decline, most fish species, including walleye, rainbow trout, gizzard shad and emerald shiner, could be affected according to the study, from 25 percent for most fish species, to 37 percent for a few plankton-eating species.

“Although the decrease is not as bad as other people thought, or compared to what happened in the Illinois River, it is not that bad — but still, it is a very bad thing, especially for the sport and commercial fish species,” Zhang said.

The same research team is now working to expand their research to predict the impact of Asian carp in the other Great Lakes, such as Lake Michigan, Lake Huron and Lake Ontario. They are also working on a study of the regional economic impacts stemming from Asian carp in Lake Erie.

Zhang’s research This project was funded by the Environmental Protection Agency through the Great Lakes Restoration Initiative and the NOAA’s Center for Sponsored Coastal Research.