If Asian carp are present in Lake Erie, they will likely leave a trail of evidence behind. That's what those working with the Ohio and Michigan departments of natural resources and the U.S. Fish and Wildlife Service are searching for as they conduct water sampling, electrofishing and netting surveys. The search of portions of the lake's western basin and two of its tributaries will last two weeks.
No reports of live Asian carp have been substantiated in Lake Erie since 2000, according to Rich Carter of the Ohio DNR, although there have been other reports of live bighead carp in the lake as late as 2003. But environmental DNA evidence of silver and bighead carp was discovered last August in samples taken in north Maumee Bay in Michigan and in Sandusky Bay in Ohio.
Now officials are searching in the Maumee and Sandusky rivers and their adjacent bays and plan to collect 500 samples to analyze.
"Our coordinated sampling efforts with partner agencies are very important in order to revisit areas where positive samples were collected last year, and to expand sampling to areas that may be reproductively favorable for bighead or silver carp," Tammy Newcomb, Michigan DNR research program manager, said in a news release. "These are the areas where we can be most effective in preventing expansion of these species, should they be present."
Results from last year's sampling, which includes taking jars of water and filtering out things like scales, mucous and excrement, were announced last month. Two samples from Michigan waters tested positive for silver carp environmental DNA, and four samples from Sandusky Bay were positive for bighead carp DNA.
Carter, executive administrator for fish management and research at the Ohio DNR's Division of Wildlife, said the testing was developed in 2009 by the University of Notre Dame. He noted that the limited number of laboratories able to review the 417 samples collected last year could explain the delay in getting results. He also said that Chicago waterways, rather than Lake Erie, have seen much of the focus in efforts to search for Asian carp. At least some of the carp are thought to have escaped from southern aquaculture facilities after being imported in the 1970s. They are invasive fish that experts fear could devastate the sports fishing industry in the Great Lakes, which have a $7-billion fishery, according to the Michigan DNR.
Silver and bighead carp "eat the microscopic plants or animals that form the base of the food chain for many of the fish in Lake Erie, but in particular sport fish at young ages, so they have the potential to out-compete other fish and in particular damage our sport fish populations," Carter said.
Carter said there have been three substantiated reports of commercial fishermen catching live bighead carp in Sandusky Bay in Ohio and near Pelee Island in Ontario, but those were adult fish rather than young fish.Young fish could indicate that the carp are reproducing in the area.
"Since 2000, we have not seen another live fish in Lake Erie, and I think the important thing to note is we do a tremendous amount of sampling historically and that sampling is ongoing. And in all our surveillance, we've not seen Asian carp," he said.
If silver or bighead carp were to establish themselves in Lake Erie, there are no physical barriers to prevent them from traveling north into the Detroit River and Lake St. Clair.
Swimming against the current has not proven to be a deterrent, as evidenced by the steady progression of the fish up the Mississippi River.