Testing in Michigan’s Marrs and Washington Lakes Show No Sign of Grass Carp Reproduction
The results from grass carp environmental DNA (eDNA) sampling done in Marrs and Washington lakes in Lenawee County was negative, according to the Michigan Department of Natural Resources, Fisheries Division. These samples were collected as a result of earlier observations and collections of grass carp in Marrs Lake in May and June 2012.
“The results of the eDNA testing in Marrs and Washington lakes, in combination with the physical surveys performed on Marrs Lake in 2012, are encouraging,” said Todd Kalish, Lake Erie Basin Coordinator. “No juvenile grass carp were observed or collected during the surveys and the large adult fish that were collected were limited in number and old in age.”
Grass carp are considered an Asian carp species and, while they do not pose the same risk to Michigan’s waters as bighead or silver carp, they are of concern as they eat beneficial types of aquatic plants and alter good fish habitat.
Fisheries Division believes that while grass carp have probably been in Marrs Lake for more than a decade at very low abundance, they have been unable to establish a viable population.
After receiving a report of grass carp in Marrs Lake in early 2012, Fisheries Division developed a Grass Carp Management Plan for the lake that included fisheries surveys and directed efforts to remove them. Fisheries Division conducted surveys and removal efforts during the weeks of June 18 and July 19. Two adult grass carp were collected during those efforts, and genetic testing confirmed both fish were reproductively viable. After completing the July survey, water samples were collected for grass carp eDNA analysis from Marrs and Washington lakes. Washington Lake is connected to Marrs Lake by a channel. The eDNA analysis was completed by Central Michigan University.
“If additional sightings are documented in the future, we will work with the waterfront owners and anglers to determine appropriate management actions,” said Kalish.
Fisheries Division reminds the public that grass carp are considered an aquatic invasive species and remain a concern in Michigan. Given their potential to negatively affect native fish species, native aquatic plants and fish habitat. The DNR also reminds the public it is illegal to transport, possess or stock grass carp in public and private waters.
For more information on grass carp, visit www.michigan.gov/fishid and click on Asian Carp.
