The search for Asian carp in Lake Erie has moved to the Sandusky River and Sandusky Bay, where 20 of 150 water samples collected in early August tested positive for the presence of silver carp environmental DNA, or eDNA.
Samples were also taken from the Maumee River, Maumee Bay and Western Lake Erie. The results of those samples should be available in September.
The Sandusky Bay-area positive samples prompted the Ohio Division of Wildlife fisheries experts to intensify their search for live carp.
Researchers report eDNA evidence can’t determine whether live Asian carp are swimming in Sandusky Bay, or if the eDNA was brought to the area in the bilge water of freighters or other boats, storm sewers or fish-eating birds.
The large number of positive results surprised fisheries experts, especially the makeup of the results. In water samples taken in August 2011, positive samples from Sandusky Bay were of bighead carp. This time, it was all silver carp, the invasive Asian carp that leap from the water when disturbed.
“Our responsibility is to continue the search for the source of the eDNA, and that includes additional eDNA sampling,” said Rich Carter, ODOW executive administrator of fish management and research. “The potentials are that there are live fish to be found, or that there is some other source of the eDNA.
“We’ll move forward with the next round of sampling, and we’ll expand our gear to include targeting smaller juvenile Asian carp,” said Carter.
In addition to the water samples taken earlier this month, Ohio, Michigan and U.S. Fish and Wildlife Service personnel used electrofishing techniques and put trawl and gill nets in the water to try to capture an Asian carp. That effort failed, but Carter said Ohio can’t assume there were no carp to net or shock.
Carter said that while trawl nets will catch fish of all sizes, the gill-net mesh used to target Asian carp wasn’t small enough to catch juvenile fish.
The most positive eDNA hits were in an area of Sandusky Bay near the mouth of the Sandusky River, said Carter. He plans to have survey crews focus on that area, as Ohio crews were on the water this week collecting more water samples. Netting should resume Sept. 17.
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