What do sturgeon eat? DNR finds frogs in stomach for first time

A giant sturgeon at Critters in Winneconne.jpg
A giant sturgeon at Critters in Winneconne, February 8, 2020 (WLUK/Eric Peterson)

OSHKOSH (WLUK) -- A sturgeon harvested in Lake Winneconne is giving some scientists something they haven't seen before.

Seven frogs were found inside the prehistoric fish's stomach during routine sampling.

During a typical spearing season, the Department of Natural Resources collects sturgeon stomachs, so biologists can see what the big fish are eating. Lake fly larvae, or red worms, are a common find, but this year, one fish was found feeding on something else.

"He's like, 'oh man, what's this?' And we kind of had to stop and take a look," said Ryan Koenigs, DNR Sturgeon Biologist.

Koenigs says it didn't take long to identify.

"You can tell they're frogs. There's seven of them in the pan," he said.

Koenigs says the frog find is a first for him.

"We've never observed this in any of the diet work that I've been involved with, which we've been, probably handled, sampled about 600 stomachs over the last seven seasons, so, this is kind of a rare observation," he said.

Koenigs says the sturgeon likely gobbled up the frogs in shallow sediment, near the Lake Winneconne shoreline.

"It's always interesting to see something new," he said.

Koenigs says checking stomachs is part of an effort to help manage the sturgeon population. He says during the season, giant fish get plenty of attention at the registration stations, but when it comes to the big scientific picture, every sturgeon counts. A 16.7 pound, 45 inch long fish was registered at Waverly Beach on Lake Winnebago opening day.

"It's a known-age fish," said one sturgeon registration station worker.

Scientists say the female sturgeon was hatched, raised and stocked into the Upper Fox River almost 20 years ago.

"Those are the fish that are going to be the future. Those are the fish that you need to sustain this population moving forward. Because those big fish aren't always going to be there, you need the smaller fish to grow in, to be the future bigger fish," said Koenigs.

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