To protect Lake Superior’s naturalized rainbow trout population, genetically screened steelhead-strain fish, originating from wild runs in the big lake itself, will replace the hatchery-raised Kamloops trout strain the Minnesota Department of Natural Resources now stocks to bolster fishing opportunities near Duluth.
New advances in genetic testing confirm Kamloops interbreed with wild rainbow trout. When that happens, fewer young survive and the overall steelhead population is reduced.
The change from Kamloops to stocking wild-sourced steelhead lets fisheries managers improve fishing opportunities on area streams while continuing the rehabilitation of the wild fish population.
“We have worked hard to develop a solution that respects what our diverse group of rainbow trout anglers have told us is important to them – harvest opportunities in both the stream and the boat fishery, as well as high quality catch-and-release opportunities for wild steelhead,” said Cory Goldsworthy, the DNR’s Lake Superior area fisheries supervisor.
Since 1976, the DNR has stocked the Kamloops strain of rainbow trout in Lake Superior’s waters near Duluth. Stocking increased angler opportunity and reduced harvest pressure on wild steelhead. The action helped Lake Superior’s wild rainbow trout recover from the detrimental effects of invasive sea lampreys and overfishing.
Despite only localized stocking, the stocked Kamloops genetics have shown up in samples taken from many North Shore streams, the Wisconsin Bois Brule River and Michigan waters of Lake Superior.
“These discoveries confirm that interbreeding is widespread well beyond Minnesota waters,” Goldsworthy said. “It would be irresponsible for the Minnesota DNR to keep stocking these fish that research has shown negatively impact Lake Superior’s steelhead population.”
Numerous genetic studies on the North Shore all point toward the negative impacts of interbreeding on wild steelhead populations, but DNR researchers were never able to confirm genetic interbreeding in the wild even with genetics work done as recently as the 1990s.
“With new tools, we now know without question that we can’t have a goal to rehabilitate wild steelhead populations while at the same time stock the Kamloops strain for harvest,” Goldsworthy said.
The steelhead the DNR stocks will have an adipose fin clipped off, just like Kamloops did. That process, which doesn’t harm the fish, allows anglers to easily determine what can be harvested. Unclipped, wild steelhead will continue to remain catch-and-release only – as they have been since 1997. Because of this, the stocking change means anglers will see the same harvest regulations.
The 1995, 2006 and recently revised 2016 fisheries management plans for the Minnesota waters of Lake Superior all discuss the need for continued monitoring for interbreeding between Kamloops and wild steelhead as well as re-evaluation of using the Kamloops strain should interbreeding be confirmed.
More information about the Lake Superior fishery, including the 2016 Fisheries Management Plan for the Minnesota Waters of Lake Superior can be found on the DNR website at mndnr.gov/areas/fisheries/lakesuperior.