MINNEAPOLIS (WCCO) — A stinky and unsightly problem is washing ashore in Twin Cities lakes: thousands of dead fish.

But officials say it’s nothing to worry about.

As the water warms up, a naturally occurring bacteria kills fish. This year, it’s happening a little later than usual because Minnesota had a cooler spring.

The Department of Natural Resources says the bacteria weeds out the weaker fish, so only the strong, healthy ones can continue populating the lakes. The DNR says it’s important to remember the seasonal fish kill does not affect the lake’s water quality for swimming or boating.