Thursday, February 2nd, 2023
Thursday, February 2nd, 2023

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DNR aims to increase understanding of paddlefish

St. Paul — There’s a lot that’s not known about paddlefish, those long- and hard-nosed dinosaurs swimming in Minnesota waters.

Anglers on the Mississippi River occasionally bump into these fish this time of year while walleye fishing, incidentally snagging the powerful swimmers and suggesting that paddlefish, which are on Minnesota’s threatened species list, might be doing OK.

“If anything, (the population) seems to be expanding,” said John Hoxmeier, a research biologist based out of the DNR’s Lake City fisheries office. “We have gotten some juvenile paddlefish in some of our sampling, which is a good sign. We don’t have a monitoring program set up for them. Mainly the catches we get are incidental.”

But the DNR is set to launch a program this spring that could shed new light on the paddlefish population, or populations in the state.

The DNR is hoping to learn more and be able to evaluate the species by placing transmitters into select fish, which ping strategically placed receivers that capture acoustic signals. The fixed receivers are set at various locations throughout the river system, from St. Anthony Falls on the Mississippi and Taylors Falls on the St. Croix to the north end as far south as Iowa. Some of the receivers are sunk to the bottom of the river with anchors, while others, which are removed because of ice floes, are attached to navigational buoys.

When a fish with a transmitter passes by one of the receivers, data are logged, allowing for monitoring that previously was too time-consuming. Biologists used to have to ride around on the river to pick up a signal. 

“That’s the thing with paddlefish,” Hoxmeier said. “They don’t stop at borders.”

This spring, Hoxmeier is planning on putting transmitters in 10 paddlefish from Lake Pepin.

Joel Stiras, a DNR fisheries specialist out of the East Metro office, already has tagged three fish on the St. Croix River and one fish on Pool 2 of the Mississippi, with plans to tag more fish in both of those river stretches this year.

“We are trying to get a handle on what the population is like,” Stiras said.

But there are a number of questions the DNR hopes to answer about these fish in Minnesota.

“Really, the main thing is to monitor their movements,” Hoxmeier said. “There is some thought that there are distinct populations in the rivers.”

The way that thinking goes, there could be separate populations in the Minnesota River, the St. Croix River, and up and down the Mississippi River.

“Or is it one population that uses the entire river system?” Hoxmeier said, adding that the data should allow for a survival estimate to be determined.

The DNR doesn’t know if there is suitable spawning habitat for the species in Minnesota, though Stiras suspects they use the same rock and rubble with fast-moving water that species such as lake sturgeon and walleyes prefer.

“We hope these transmitters are going to tell us that,” Stiras said, noting that some of the transmitters the DNR plans to use will give temperature and water pressure readings, allowing the department to determine how deep the fish are. “It will be interesting to see if the fish are real high up in the water column,” he said.

Another chief concern regarding paddlefish, which are at the northern edge of their range in Minnesota, is how they might be affected by invasive silver and bighead carp.

“Paddlefish would be in direct competition with them, since they are all filter feeders,” Stiras said. “So it’s kind of important to find out (as much as we can about paddlefish) before invasive carp become established here.”

The DNR also plans on working with St. Mary’s University of Minnesota in Winona, which also began monitoring paddlefish in the Mississippi River a few years ago. Currently, the program, run by professor Joshua Lallaman, has five paddlefish in the river that were tagged at Winona.

Lallaman takes his students out to monitor fish with a remote receiver, and has picked up signals from fish Stiras tagged on the St. Croix. 

“We were able to track it as it was moving from (Pool) 5A,” he said.

It took an email chain to reveal the identity of the fish to Lallaman.

“It’s a mystery,” he said. “You expect it to be one of your fish, and then it’s not. So it’s fun to track it down.”

And the point of all of this is to find out much more about this unique fish species – research that could perhaps lead to an angling season in Minnesota (there are seasons for the fish in Iowa and the Dakotas, among others).

“This is going to be the start of how they’re doing and where we need to go next,” Hoxmeier said.

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