A DNR spring fishery survey showed good numbers of walleyes.
“We didn’t see a major issue there,’’ said Deserae Hendrickson, DNR area fisheries supervisor. “One thing we definitely noticed was an increased amount of woody habitat in the water, which is a positive thing.’’ The trees, partly buried in sediment, provide fish habitat.
The event itself killed some fish, including some that were stranded in backwaters after the floodwaters subsided. “We did rescue some sturgeon and other fish,’’ Hendrickson said, “but we couldn’t get them all. But I can’t say we saw a lot of dead fish.’’
Fish reproduction likely wasn’t strong last year because of the flood, but Hendrickson said it will take a year or two to assess the impact.
Joel Hoffman, a research biologist for the U.S. Environmental Protection Agency in Duluth, was working on an invasive species research project in the estuary, surveying fish larvae, when the storm struck.
“We wondered if the fish larvae would be flushed out, but interestingly our catch rates after the flood didn’t change much,’’ he said.
Later last summer, however, Hoffman discovered the disappearance of a large amount aquatic vegetation — key habitat for young fish. “We literally couldn’t find it,’’ he said. “I’m not sure it was scouring [from floodwaters] or was a light-related affect from the turbid water.’’
Hoffman doesn’t know if the vegetation will reappear this year or if the flooding cause long-term damage. “It’s too early to tell; it’s just starting to come up now,’’ he said.
Still studying impact
Elizabeth Minor, an associate professor of chemistry at the University of Minnesota Duluth’s Large Lakes Observatory, is looking at the possible changes in the chemistry of the lake, including organics, nutrient levels, suspended solids and light penetration.
“The lake is very big and appears to be pretty resilient,’’ she said. But the jury is still out on the long-term impact.
Something else bothers her.
Of the 12 “mega-rain” events in Minnesota history, five have occurred in the past 11 years. “If you look at climate change models, we’re predicted to have more intense events,’’ she said. “The question is, if the lake keeps getting hit this way, what happens?’’
Doug Smith • firstname.lastname@example.org