Invasive Asian Carp Threatens Great Lakes; DNA, But No Fish, Found in Tributaries

DNA from the invasive species Asian carp has been found in estuaries leading to Lake Erie, though there may not be actual fish; bait shops tested.

Traces of Asian carp environmental DNA—such as mucus, scales and other fish remnants—have been found in waterways leading to Lake Erie, but environmental authorities both north and south of the Great Lakes are seeking explanations in the absence of actual fish.

If the invasive species, first brought into the U.S. in the 1970s to clean up pond scum in catfish farms and other small bodies of water, were to take hold in the Great Lakes it could spell ecological and economical disaster, authorities say.

Michigan environmental officials announced on September 24 that Asian carp environmental DNA had been found in water samples collected in July and August from Maumee Bay and the Maumee River. Water samples taken from the Sandusky Bay and the Sandusky River during the same two months also yielded DNA samples, the Michigan Department of Natural Resources said.

However, no actual fish have been spotted, and given that a recent study found no major ways for the carp to make it through to the lakes, officials are mystified. Bait shops are being tested to see if the DNA is getting in that way, the Detroit Free Press reported on September 6. The worry is that an invasion of Asian carp could devastate the $7 billion Great Lakes fishery industry.

“Our field crews were out on the water numerous times over the last couple of months, using multiple gear types and they found no live Asian carp,” U.S. Fish and Wildlife Service Midwest Deputy Regional Director Charlie Wooley said in a press release. “We are still trying to pull back the curtain on what the source is for these positive eDNA samples.”

The U.S. Army Corps of Engineers studied 18 canals, ditches and other waterways between the Great Lakes and Mississippi River and found that they did not seem viable for the carp to travel between the two giant river-drainage basins, the Associated Press reported on September 14.

Nevertheless, because Eagle Marsh could possibly connect the carp-ridden Wabash River with the Lake Erie tributary Maumee River, officials have installed a chain-link fence across the marsh, the AP said.

Unlike northern pike, which are invading Kalispel Tribe territory in the northwest, Asian carp are edible. And catching them is not as hard as one might think. The fish have earned themselves the moniker “flying carp.” Riled by vibrations from passing boats, they leap out of the water, smacking people and flopping around on the deck. Given their weight of 20 to 40 pounds, they have been known to injure boaters.