The results of the most recent testing of the Sandusky Bay and Sandusky River for the presence of silver carp environmental DNA indicate 20 of 150 samples are positive, the Ohio Department of Natural Resources has announced.
The ODNR, Michigan Department of Natural Resources, U.S. Fish and Wildlife Service, and U.S. Army Corps of Engineers collected the samples from the bay and river on July 30 and 31 as part of an extensive effort earlier this summer to collect data on Asian carp in Sandusky and Maumee bays in western Lake Erie.
Environmental DNA (eDNA) is the genetic material from organisms that can be detected by sampling the environment.
No Asian carp were found after the agencies conducted test netting and electro-fishing.
As of last week, eDNA sampling results from the Maumee Bay were being analyzed.
“We will continue to address the uncertainties about the status of Asian carp in Lake Erie with our partner agencies,” said Rich Carter, the ODNR’s executive administrator of Fish Management and Research. “This includes ramping up our research efforts for live fish or other sources of eDNA. We will keep working with our angling public to be vigilant in watching for these species.”
In light of the positive samples, the agencies have discussed plans for more research work this month, he said, including additional eDNA testing.
The agencies plan to also continue working together to assess the current status of bighead and silver carp in western Lake Erie bays and tributaries.
While eDNA analysis provides a tool for early detection of Asian carp at low densities, and the latest positive results raise concern about the presence of the carp in western Lake Erie, it can’t provide information about the number or size of possible fish, researchers say.
Currently, the evidence can’t verify whether live Asian carp are present or whether the DNA may have come from a dead fish or whether water containing the DNA may have been transported from other sources such as bilge water, storm sewers, or fish-eating birds.
The Corps of Engineers, Fish and Wildlife Service, and U.S. Geological Survey are heading a two-year program, called the Asian Carp Environmental DNA Calibration Study, to shed more light on the results.
Jim Dexter, fisheries chief of the Michigan DNR, said the breadth of positive samples from the Sandusky Bay “was not expected.”
Since no live fish have been linked to the sampling, researchers say the data suggest if Asian carp are present they are not abundant.
According to a control plan prepared in 2007 by the Asian Carp Working Group, seven species of Asian carp have been introduced to the U.S. The planning document focuses on four: the black carp (Mylopharyngodon piceus), bighead carp (Hypophthalmichthys nobilis), grass carp (Ctenopharyngodon idella), and silver carp (H. molitrix).
Feral bighead, grass, and silver carps have all established reproducing populations in several major rivers of the United States.
Anglers are being encouraged to learn to identify Asian carp, including adults and juveniles, as the use of live bait buckets has been identified as a possible source of entry into the Great Lakes.
To contact the ODNR about an Asian carp caught or observed, call 1-800-WILDLIFE.