Michigan: Thornapple Lake Selected for Muskellunge Broodstock
Thornapple Lake is a 409 acre lake that lies in eastern Barry County, about five miles west of the village of Nashville. It is a popular recreation lake with two boat launches and shore fishing opportunities.
The lake originally supported a native Great Lakes-strain muskellunge population until it declined in the 1950s. Stocking of Northern-strain muskellunge in Thornapple Lake began in 1964, and the lake was used as a muskellunge broodstock source from the early 1970s to 2010.
Each spring, Department of Natural Resources biologists collected eggs from muskellunge in Thornapple Lake and then reared the offspring of these fish at Wolf Lake State Fish Hatchery in Mattawan.
In the fall, these fish were stocked throughout the state to support muskellunge fisheries. Recently the DNR implemented a program to stock only native Great Lakes-strain muskellunge in waters connected to the Great Lakes to reduce the potential for negative genetic effects on naturally reproducing muskellunge populations.
Currently, the Great Lakes muskellunge eggs for Michigan’s state fish hatcheries are collected from fish located in Lake St. Clair and the Detroit River. There are two disadvantages with the current system. The muskellunge are hard to locate in such a large system, and the late spawning period for fish in these Great Lakes connecting waters reduces the rearing period in the hatchery and, thus, the size of the muskellunge at the time of stocking into other waters. (Please note, 2017’s egg collection efforts have been cancelled due to a disease outbreak.)
Thornapple Lake was chosen as a preferred location for broodstock establishment to meet the increased demand for Great Lakes-strain fish. The DNR began stocking Great Lakes-strain muskellunge in Thornapple Lake in 2011 and has stocked 9,613 fish to date.
These fish were expected to thrive due to the diverse community of prey fish available and the past success of the Northern-strain stockings. However, surveys of Thornapple Lake conducted in 2016 saw 97 muskellunge collected and only four were confirmed as Great Lakes-strain. Low survival of juvenile Great Lakes-strain muskellunge could be due to the high density of adult Northern-strain muskellunge (along with moderate numbers of northern pike) resulting in predation and competition for resources.
In an effort to increase survival of the Great Lakes-strain brood stock, the DNR, Fisheries Division’s Southern Lake Michigan Management Unit relocated 66 Northern-strain muskellunge from Thornapple Lake and introduced them into Lower Crooked Lake in Barry County in April 2017. Four Great Lakes-strain muskellunge were captured and released back into Thornapple Lake.
Twenty-eight northern pike also were collected during the muskellunge transfer efforts. These fish were released into the Thornapple River downstream of the Irving Dam.
The fish were collected with trap nets and transferred to recipient waters in hatchery trucks. The objectives of the project were to improve survival of stocked Great Lakes-strain broodstock in Thornapple Lake and to enhance the muskellunge fishery in Lower Crooked Lake.