Grand Lake just west of Duluth had another fish kill over the winter, but this one wasn't as extensive as 2014.
That's the word from Dan Wilfond, Minnesota Department of Natural Resources fisheries biologist in the Duluth area.
Wilfond said his office started getting calls in March reporting fish in trouble on the 1,600-acre lake located between Twig and Saginaw. DNR staff found low levels of dissolved doxygen in parts of the lake. The assessment was that it was mostly bullheads and bluegills and that most gamefish were spared.
The problem is that Grand Lake is very shallow and very weedy, which can be a bad combination in hard winters. When snow piles up on the lake and blocks sunlight, the weeds begin to die off rapidly. And instead of releasing oxygen as they do when they are alive, the decaying plants actually consume oxygen. That robs dissolved oxygen from the fish and other critters.
That happened in the winter of 2013-2014 on Grand Lake and an estimated 35,000 fish died, including walleyes, bass, crappies and bluegills. The DNR then restocked the lake with walleyes, 750,000 fry each year between 2014-2016, although it's not considered a prime walleye lake. The lake is most popular for its pike fishing.
"Pike and perch seem to be able to handle it (lower oxygen levels) better and they have been okay in Grand,'' Wilfond said. Crappies also seemed to survive the 2014 kill well.
Most of Grand Lake, nearly 99 percent, is less than 15 feet deep, and most of that is less than 10 feet deep, Wilfond noted, shallow enough to get weed growth across most of the basin. Wilfond said the lake has one deeper trough, at 24 feet, and also some springs that provide an inflow of oxygen and some relief for fish even in tough years.
"We had been hearing, going into this winter, that fishing was rebounding after the big (fish kill) in 2014,'' Wilfond said. "I don't think this one was nearly as bad."
Wilfond said that, while it may be difficult to appreciate seeing dead fish floating if it's your favorite lake, small fish kills in some "overcrowded'' lakes can be a good thing, eliminating a few of the many small fish and making more space and food available for bigger fish.
Grand Lake is less like most northern Minnesota lakes and more like southern lakes in the state and likely will continue to have fish kills during heavy-snow winters.
"It probably always has to some extent,'' he noted.