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After inbreeding, DNR changing how it stocks Lake Superior trout

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Steelhead
Steelhead trout
Courtesy of the University of Minnesota Press / Illustrator Joseph Tomelleri

The Minnesota Department of Natural Resources is changing how it stocks rainbow trout in Lake Superior after studies revealed that two different types of trout were interbreeding.

The agency says it will switch to the genetically screened steelhead-strain fish and hold off on stocking Kamloops trout, which comes from hatcheries. The steelhead variety originates from the lake itself.

"We know that wild steelhead are spawning with our stocked Kamloops that are out there. So we know integression is widespread along the north shore, and it's also in other jurisdictions as well," said Cory Goldsworthy, a DNR fisheries manager.

That's threatening previous efforts to help Lake Superior's wild rainbow trout population recover, according to the DNR. The department's latest genetics study revealed that when the two varieties mix, fewer young trout survive. 

While the decision might not sit well with some angler groups, especially those who favor Kamloops trout, Goldsworthy said it's a longstanding issue that needs to be addressed.

"The first rainbow trout genetic study was done in 1993, looking at genetic structure and hybridization of rainbow trout populations," he said. "So, the history we have with genetic science or genetic studies on rainbow trout is strong. And the science from this recent study just couldn't be ignored either."

The steelhead that are stocked will be clipped, the DNR said. That way, anglers can identify what fish can be harvested.

The DNR says the stocking change will have no impact on harvest regulations, meaning wild steelhead will continue to fall under catch-and-release rules.