Lake trout no longer stocked in northeastern Minnesota waters

A MN DNR employee holds a lake trout on Mountain Lake in the Boundary Waters, as part of the annual effort to harvest eggs to raise fish for stocking at a hatchery in southeastern Minnesota. (MN DNR photo)

The Minnesota Department of Natural Resources has decided to discontinue stocking of lake trout in Cook County, at the very northeastern corner of Minnesota, including lakes in the Boundary Waters. The decision is based on the success of restoring the fish populations in many lakes, and failure in others.

In several lakes in the area, lake trout are reproducing naturally so well that they no longer need stocking. But other lakes have repeatedly rejected efforts to build up the population, due to a few factors. The news was first reported on WTIP, which quoted Cook County fisheries interim area supervisor Matt Weberg. “We’ve basically considered all of our lake trout lakes naturalized or if they’re a native lake, persisting at abundances we consider acceptable,” Weberg said.

Stocking yielded mixed results

By tagging or clipping the fins on stocked fish, and then counting the number of stocked fish caught in surveys, the DNR saw that their efforts were insignificant compared to natural reproduction. Lake trout in water bodies including Moss, Mayhew, and Ram have all thrived, according to the DNR.

“We started to see the population completely dominated by naturally produced fish and at abundance levels we’d identified as goals in our lake management plans,” Weberg told WTIP.

But other lakes resisted multiple efforts to establish a healthy lake trout population. The DNR has no plans to continue stocking lakes including Poplar, Flour, and East Bearskin, and Hungry Jack Lakes. Amongst several reasons that the stocking won’t work, fishery managers blame introduced fish species that compete with trout.

“Lake trout tend to do best in the simplest of setting, so the addition of predator species like walleye and smallmouth bass, in combination with lakes with limited habitat with depth and cold,” have worked against reintroduction, Weberg said.

Most lake trout stocked in northern Minnesota lakes originate in Mountain Lake in the eastern Boundary Waters. The DNR annually travels to the border water in early spring to harvest eggs from spawning fish, which are then raised in a hatchery in southeastern Minnesota.

Watching the fish population

Weberg said, while the agency will no longer plan to stock lake trout in the Cook County lakes, they will continue conducting surveys and monitoring the population. If declines are observed, stocking could resume.

Additionally, Weberg said climate change continues to be a big threat to lake trout in the area. Many of Cook County’s lake trout lakes are relatively small and shallow for lake trout. As global warming continues in the future, they might lose the cold, well-oxygenated waters they depend on to survive hot summer weather.

“As these smaller lakes are squeezed, the amount of optimal habitat for lake trout is very reduced, some of them might reach a tipping point,” Weberg said.

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