Survival of large lake trout as good as the small ones in Lake Michigan
Ann Arbor, MI — Great Lakes' lake trout populations are being enhanced through stocking of hatchery-reared fish to rebuild populations and develop self-reproducing stocks.

In Lake Michigan over 2 million lake trout have been stocked annually for decades by the USFWS for this restoration effort. These fish enter the lake as yearlings (about 14 months old) and were previously stocked at size of 44 fish/kg. It was thought that raising and stocking larger fish (about 24 fish/kg) would increase the post release survival of these fish in the lake, which would require fewer fish to be raised and reduce crowding at the national fish hatcheries.

Fishery biologists from the USFWS and the Wisconsin DNR teamed up to test whether survival of the larger lake trout was greater than the smaller fish. Paired stockings of uniquely tagged small and large lake trout were released in Lake Michigan and recovered over many years to determine relative survival. Recapture rates indicated that relative survival of the two groups was similar, and that stocking larger fish did not benefit the restoration program.

"Apparently the size difference we tested did not benefit survivorship of lake trout, and their overall health condition at stocking is likely more important than size," according to FWS Biologist