Silver Asian carp are shown jumping out of the water in the Illinois River in 2007. The local positive results don't necessarily mean live carp are present.
For the third consecutive year, at least one Toledo-area water sample has come back positive for microscopic Asian carp genetic material — this time, near the heart of downtown, next to the northeast corner of the Martin Luther King, Jr., Bridge.
Is that anecdotal or alarming information?
Great Lakes scientists don’t know. They admittedly are struggling now to put dozens of positive readings logged over the last four years, first in Chicago and then in northwest Ohio, into the right perspective. But they stand firm behind a relatively new type of technology that generated the results as one of their most powerful tools for heading off a potential Asian carp invasion.
Positive hits for Asian carp genetic material are more than anecdotal but less than ironclad proof that highly destructive Asian carp have found a way into the Great Lakes, scientists said.
Scientists said they see any positive result as a warning flag. Yet it’s been 13 years since the last known live Asian carp were caught in the Great Lakes. Three older bighead species — possibly illegal releases — were caught by commercial fishermen in western Lake Erie between 1995 and 2000, two in Ohio water and one near Ontario’s Pelee Island, said Rich Carter, executive administrator of the Ohio DNR’s fish management and research.
Charlie Wooley, U.S. Fish and Wildlife Service deputy Midwest regional director, said the most important thing is that no evidence has emerged that a breeding population is being established. That’s considered the worst-case scenario, Mr. Wooley said, because scientists fear there would be no stopping Asian carp from colonizing the lakes — as they have other bodies of water — if that happens.
What’s emerged, he said, is a fascinating discussion about how a highly sophisticated and relatively new research tool used to hunt down one of North America’s most dreaded invasive species is yielding data faster than what scientists know to make of it.
“To a certain extent, we’re almost running a grand scientific experiment now,” Mr. Wooley said of genetic mapping in the wild known as environmental DNA, or eDNA.
Jeff Tyson, Lake Erie fish-management program administrator for the Ohio Department of Natural Resources, agreed the big-picture story that’s being played out now is one of the most important case studies in risk analysis for battling invasive species.
“The eDNA technology is extremely useful, but it’s evolving,” Mr. Tyson said.
Developed by some University of Notre Dame top scientists, eDNA is a highly sensitive measurement of Asian carp fish scales, cells, feces, or mucus found in the top two inches of the water column. It is based on the molecular composition of the water and might be useful for warding off threats from other invasive species, scientists said.
The test was first put into use for Asian carp in 2009 near the Chicago area, when the U.S. Army Corps of Engineers — which operates electrical barriers there in hopes of keeping northerly migrating carp from getting into Lake Michigan — hired Notre Dame to do fieldwork.
The first round of sampling rocked Great Lakes policy-makers because Notre Dame found genetic evidence of carp beyond the barrier, a result the Corps did not anticipate.
The eDNA method of detecting genetic material was ruled scientifically accurate, despite the Corps’ challenge. It was peer-reviewed and published in Conservation Letters, the flagship academic journal of the Society for Conservation Biology, and was vetted by the U.S. Environmental Protection Agency.
Positive results confirm Asian carp genetic material is present.
But scientists can’t tell if those microscopic bits and pieces came from live or dead carp, one fish or multiple ones, those of a breeding age or not.
The presence of eDNA conceivably can come from a number of pathways: bilge water, storm sewers, or illegal releases, to name a few.
Even the excrement of fish-eating birds that might have fed on dead carp miles away has been touted as a theory. Some scientists agree that is one of the more unlikely scenarios, yet say they cannot dismiss it until they know more about how eDNA gets into the water.
“What this data tells us is we need to remain vigilant,” Mr. Carter said. “If you take a step back, what we’re looking at is the repeatability of the eDNA over time.”
Testing moved into Toledo-area waterways in 2011, driven largely by fears that Asian carp in Indiana’s Wabash River could get into the Maumee River when flooding in the vicinity of Fort Wayne Eagle Marsh connects those two waterways. It also has been conducted elsewhere across the Great Lakes region, including Michigan’s Kalamazoo River, Muskegon River, St. Joseph River, and Grand River; the Lake St. Clair-Detroit River corridor, and three western Lake Erie tributaries that are in Michigan (Belle River, the Black River, and the Swan River). Nothing was found in the Kalamazoo. Results on others are expected later this year, the Michigan DNR said Thursday.
No Asian carp are known to be in the Maumee. But 2011 sampling results yield four positive hits for bighead Asian carp in Lake Erie’s Sandusky Bay and two positives for silver Asian carp in Lake Erie’s Maumee Bay. In 2012, the number of hits swelled to 20 positives for silver carp in Sandusky Bay, and three positives for them in Maumee Bay, Mr. Carter said.
Maumee River key
State and federal officials see mouths of the Maumee and Sandusky rivers in northwest Ohio as key battlegrounds, because they have some of the Great Lakes region’s prime habitat for spawning, Mr. Carter said.
The lone positive was drawn near the Martin Luther King Bridge, one of 225 samples taken in the Maumee River by the federal wildlife agency and the Ohio DNR between downtown Toledo and Perrysburg June 25 and 26.
Another 100 taken from the Sandusky River on June 24 were negative, he said.
Mr. Wooley said he characterizes the three years of Toledo-area data as “perplexing and befuddling.”
The U.S. Fish and Wildlife Service and the Ohio DNR has “put hundreds and hundreds of hours into research there and can’t find a live fish,” he said.
Jeff Reutter, director of Ohio Sea Grant and Ohio State University’s Stone Laboratory on Lake Erie’s Gibraltar Island, said this year’s lone positive in the Maumee River generates bittersweet feelings among researchers.
It is conceivably good news, perhaps even a sampling error, he said.
But until researchers can’t dismiss any possibilities, he said.
“I have the sense that if we had enough for a breeding population we’d have a lot more positives or we’d be collecting Asian carp,” Mr. Reutter said. “[But] I don’t think anyone’s really comfortable saying there’s no chance at all of Asian carp there because we’ve got eDNA.”
This December, the Corps is to release its long-awaited recommendations to Congress for permanent Asian carp solutions. Those are to include the agency’s thoughts on whether a separation of the Great Lakes and Mississippi River basins is necessary. A report submitted to the Great Lakes Commission said it could be done for $9.5 billion, less than some of the nation’s biggest highway projects.
A much more modest project is being contemplated for the Fort Wayne area. The Corps is expected to decide on one of two alternatives for keeping the Wabash and the Maumee apart, both of which promote construction of earth berms. A chain-link fence now serves as a temporary barrier.
Contact Tom Henry at: firstname.lastname@example.org or 419-724-6079.