Department of Natural Resources
Feb. 27, 2020
Environmental DNA (eDNA) testing by the Michigan Department of Natural Resources and the U.S. Fish and Wildlife Service revealed no evidence of genetic material from bighead and silver carp – two species of invasive Asian carp – in Houghton Lake in Roscommon County, Long Lake in Hillsdale County or Cass Lake in Oakland County. The retesting, which occurred from October to December 2019, was in response to results of similar surveys previously conducted as part of an aquatic invasive species early detection project conducted collaboratively by the DNR and Michigan State University.
As part of a study comparing traditional fish surveys using nets and electrofishing to eDNA sampling, the DNR and staff from MSU sampled 22 inland Michigan lakes from 2016 to 2019. Almost all the lakes showed no presence of invasive carp eDNA.
|However, the MSU results indicated that one sample each from Houghton, Long and Cass lakes contained DNA from the Hypophthalmichthys genus, which includes invasive bighead and silver carp. The lab analyzed 37 samples from Long Lake, 48 samples from Houghton Lake and 40 samples from Cass Lake.
“While a positive eDNA sample does not necessarily represent the presence of live fish, we use the eDNA results as one piece of information to determine the best response to the potential threat of an invasive species,” said Seth Herbst, DNR aquatic species and regulatory affairs unit manager.
Confirmation by the Whitney lab prompted the DNR and USFWS to undertake repeat sampling on all three lakes. Follow-up sampling of Long and Houghton lakes in 2019 found no silver or bighead carp eDNA in the 40 samples taken at Long Lake and the 430 samples taken from Houghton Lake.
Results of repeat sampling of Cass Lake in October 2019 indicated that one of the 120 samples taken was positive for silver carp eDNA. The positive sample came from the southeast portion of the lake, within approximately 200 meters of the 2018 sample that was positive for bighead carp. Quality assurance protocols in the sampling process and laboratory analysis give no indication the results were in error.
An additional 60 samples taken from Cass Lake in December 2019 showed no bighead or silver carp eDNA.
|Repeated detections of the same species over time would increase the concern of potential live individuals being present. “Based on the current information, it is unlikely that there are live bighead or silver carp in any of the three lakes,” said Herbst.
Since 2013, the USFWS has collected thousands of eDNA samples in the Great Lakes and its tributaries. Results from eDNA sampling, available at FWS.Gov, do not suggest the presence of established populations of bighead or silver carp in the Great Lakes.
No live bighead, silver or black carp have been captured through many efforts including commercial fishing, recreational angling observations and scientific sampling in any of the Great Lakes since 2002. Similarly, no bighead, silver or black carp have been caught in any of the thousands of fish population assessments conducted in Michigan’s inland lakes during that same time frame.
The DNR is planning additional monitoring of Cass Lake in spring 2020 and will increase public outreach in the area to remind lake users to clean, drain and dry boats and gear and properly dispose of bait in accordance with state laws – measures that help limit the spread of invasive species.
All anglers are encouraged to learn how to identify invasive bighead and silver carp and report any suspect fish. Identification and reporting information can be found at Michigan.gov/InvasiveCarp.
Due to their large size and high reproductive rates, bighead and silver carp pose a significant threat to the Great Lakes and Michigan’s inland lakes. They disrupt the food chain that supports native fish such as walleye, yellow perch and lake whitefish. Jumping silver carp can also injure boaters.
“Along with our participation in eDNA surveillance efforts, we continue to be diligent with early detection efforts, such as conducting fish population surveys, increasing awareness among anglers and maintaining an invasive carp reporting website for anglers to share any suspicious catches or observations that occur during their outings,” said Herbst.