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Why are so many fish dying in Minneapolis' Cedar Lake?

One person reported seeing hundreds of dead fish along the shore.

One person reported seeing hundreds of dead fish along the shore. parkypark1, Reddit

Cedar Lake is a little patch of calm in Minneapolis’ Kenwood neighborhood. Bikers and runners love the trails, and kids love its beaches. But some are noticing it's a little too calm for comfort.

Last week, Reddit user parkypark1 saw “hundreds” of dead fish on the shore. A photo showed weeds and algae peppered with pale corpses, caught in the mix among discarded candy wrappers and fallen leaves.

“I’ve been in the area about two years now and have never seen anything like it,” parky wrote.

It turns out parky wasn’t the only one who noticed. Minnesota Department of Natural Resources spokesperson Harland Heimstra says the department received reports of a fish die-off from “multiple park staff.” Heimstra didn’t know about hundreds, but there were quite a few dead fish to be seen – especially crappies. They’ve sent specimens off to the pathology lab.

What’s killing them? “We’re not sure.” 

There are any number of suspects, but the most likely is a strangulation of sorts. The department recently had a fish crew on an unrelated visit to Cedar Lake, and they discovered oxygen levels from 12 feet deep to the bottom (about 50 feet) were “very low.”

“That can happen in the summertime,” Hiemstra says. Warm water is generally worse at holding oxygen, and decaying vegetation and algae – in their heyday during hot months – tend to produce oxygen-gobbling bacteria that can suffocate organisms like fish.

It paints a macabre picture, but Hiemstra cautions not to worry too much. Fish kills are a “common, normal thing,” especially this time of year. Even if the Cedar Lake kill looks like a massacre on the surface, these die-offs tend to only cull a small percentage of the lake’s denizens each year, and the ecosystem usually recovers on its own.

“We do not believe there’s any cause for alarm at this point,” he says.

But if you see any more clusters on your lakeside hikes, feel free to call 1-800-422-0798.