Lake of the Woods, Rainy Lake and Red Lake each have physical features that should make their walleye populations more resilient in an era of changing water temperature and increasing water clarity.
That’s the message Department of Natural Resources scientist Gretchen Hansen will deliver Thursday in Duluth at a statewide meeting of the DNR Fisheries staff. She said she will continue to expand her study of Minnesota’s largest walleye lakes despite accepting a new job as a researcher and professor of fisheries ecology at the University of Minnesota.
In a public presentation for the DNR earlier this year, Hansen said a decline in the Mille Lacs walleye population coincided closely with significant increases in the lake’s water clarity. The species thrives best in lowlight, nutrient-rich, cool water and the changing optical conditions have reduced the amount of walleye habitat in Mille Lacs, she said.
But if water clarity increased significantly in Lake of the Woods or Rainy Lake, there would still be enough habitat to support the existing walleye populations in those lakes because they have more complicated, diverse depth profiles with lots of surplus habitat.
“The main thing I would say at this point is that each of these lakes is different as to how they will respond to these kinds of changes,” Hansen said. “Our large lakes are pretty diverse.”
She said walleyes in dish-shaped Upper Red Lake swim in limited habitat defined in a narrow range of depths. But the water there is so turbid, she said, it’s not at risk of clearing up.
Hansen also is studying the food chains, or food webs, in Minnesota’s largest walleye lakes. Next month, crews will conduct field work for the study on Cass, Winnibigoshish, Kabetogama, Lake of the Woods, Rainy and Vermilion lakes.
Hansen also will be part of a Minnesota research team that travels next week to Vancouver, British Columbia, to discuss physical, chemical and biological responses to multiple environmental changes in Minnesota lakes. The international conference is hosted by the Association for the Sciences of Limnology and Oceanography.