There are no recent mug shots of these intruders, no sting operations that have caught them in the act, and no criminals to perp walk in front of the cameras in handcuffs.
No one is really certain if they are there . . . or not. But Asian carp keep leaving the loose equivalent of aquatic fingerprints behind, so the stakeouts and the sweeps continue in the waters of Lake Erie and the major rivers that feed into it.
The recent analysis of another round of water samples taken this summer from Maumee Bay and the Maumee River showed that three out of 350 of the samples tested positive for the environmental DNA of silver carp, one of the most invasive of the Asian carp species.
“I’m very concerned about this, and it’s been a concern for quite some time because this eDNA evidence just keeps showing up,” said Paul Pacholski, a charter fishing captain based in Erie, Mich., who fishes throughout Lake Erie’s rich western basin.
“It’s very serious because most of these places where they are getting these positives have been recognized as places where you really don’t want the carp to get to.”
Environmental DNA could be present in the lake, bay, and rivers due to bilge water, sewage runoff from restaurants where the fish have been cleaned, or the scales, mucus, or waste from the fish or birds that have fed on the fish. But with the closest known established population of Asian carp nearly 200 miles away in the Ohio River, the presence of the eDNA remains a mystery.
“We are still trying to pull back the curtain on what the source is for these positive eDNA samples,” said Charlie Wooley, the U.S. Fish and Wildlife Service’s midwest deputy regional director.
The most recent positive hits for Asian carp continue a very disturbing trend. In mid-July, six samples from Sandusky and Maumee bays tested positive for Asian carp — four from Sandusky Bay showed the presence of bighead carp, the other species besides silver carp that is regarded as potentially the most destructive.
Asian carp can dominate the waterways by out-competing native baitfish and juvenile gamefish for food.
Two samples from that mid-July series of tests showed silver carp eDNA in north Maumee Bay, in Michigan waters. In late July, 20 samples from a group of 150 taken in Sandusky Bay and the Sandusky River also showed the presence of silver carp eDNA.
An intense period of electro-shocking and netting in the test areas has followed the positive hits, but no Asian carp have been found.
“This is all very puzzling, and at the same time it is increasingly disconcerting,” said Marc Gadsen, communications director at the Ann Arbor-based Great Lakes Fisheries Commission.
“This Asian carp DNA has to have some way of getting there.”
The possibility of Asian carp reaching the Great Lakes and establishing a population there, threatening the $7 billion sportfishing industry, has prompted an “all hands on deck” reaction from the local, regional, state and federal agencies involved in managing and protecting the vast waterway.
The Ohio Department of Natural Resources, Michigan Department of Natural Resources, U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers are collaborating in the ongoing sampling and testing on Lake Erie.
“I have been impressed with the way the agencies responsible for Lake Erie are working together on this,” Gadsen said. “They are operating on a worst-case-scenario, and I think that response is quite appropriate.”
Pacholski said the consortium of state and federal entities are now working more closely with the commercial fishermen who regularly net the lake — the individuals most likely to encounter live Asian carp — and he expects that relationship will improve the chances for an early response to any confirmed presence of the fish in the lake.“The commercial fishermen are now on high alert, so I know there is a concerted effort to get everyone involved,” Pacholski said. “I believe the biologists and the fisheries people have been doing their due diligence on this, which is to their credit.”
Gadsen said the eDNA testing and the intense efforts to comb certain areas in search of adult Asian carp should continue with the highest of priorities.
“It is important for them to keep searching because this has the potential to really change Lake Erie, if these fish are present,” Gadsen said. “This issue is the kind of thing that keeps you up at night."
Contact Blade outdoors editor Matt Markey at: firstname.lastname@example.org or 419-724-6068.