November 1, 2013
The years-long story of invasive Asian carp getting closer to infiltrating the Great Lakes moved forward this week. The U.S. Geological Survey found one species, grass carp, reproducing in the Lake Erie basin—specifically the Sandusky River in Ohio.
Grass carp have long been a favored species in backyard ponds and small bodies of water in order to control vegetation. Although a non-native species, they're legal in some states, but the variety that are legal to stock are sterile.
Late last year though, a commercial fishing operation in Lake Erie caught several specimens that, after being turned over to the USGS, were found to be fertile . Researchers don't know how the fertile fish wound up in the lake, but the concern is the potential that they may begin to reproduce.
"The problem when you have a reproducing population of grass carp is that you can't control that," says Duane Chapman, a researcher at the USGS. “They’re sitting reproducing and reproducing and producing more and more fish. And when they get to too high of a number, they will mow down virtually all of your aquatic vegetation, and that’s a problem.”
Lake Erie already suffers a lack of vegetation, and the prospect of losing what's present has Chapman worried. An increase in algal blooms, heightened shoreline erosion, and a detrimental impact on ducks and other large aquatic birds can all occur if vegetation is curtailed.
It's not all bad news, however. It’s not uncommon for an invasive species to exist in low levels for extended periods of time. An “exponential growth phase”—when the population skyrockets and begins to cause problems—does not invariably occur in every situation.
“Is this the beginning of an exponential growth phase, or is just a blip on the screen and they will never become a problem?” asks Chapman. “We just don’t know yet, and that’s something we hope to know in the next year or two.”
Chapman says that the new research can help curtail future problems.