Some observers at Clark Lake have noticed more dead fish this year than usual. To get answers, the Invasive Species Committee’s John Deming looked into it. Steve Hanson is a marine biologist who works for PLM, the company that treats Clark Lake to rid it of invasive weeds. Steve comments “several lakes, treated and not treated, had some degree of fish kill this spring. It had more to do with the inconsistent water temperatures than anything. Most were happening when we had high temperatures after extended cold periods. Since the ice came off most lakes early this year, these die offs were not related to oxygen depletion. Wildly fluctuating water temps are very stressful on fish, especially coming out of winter and being geared up to spawn. Usually it affects the fish that already have weakened immune systems or bacterial/viral infections.”
Clark Lake was not treated for weeds in 2017 or this year, 2018.
Steve continues “Interestingly, Devils and Round lakes had die offs of the majority of their redear sunfish. I didn’t see any other species. We are at the northern end of their range and they are only here because the DNR stocks them. Something about this spring was detrimental to the redear in those lakes. I know they have been stocked in Clark Lake as well.” He suggests they could be “the majority of fish that were seen dead.”