Study to reveal where St. Louis River muskies roam, feed

As muskies go, he was a beautiful specimen. A big male, 46 inches long.

His day was about to change. Already he was lying belly-up in a wooden trough that served as an operating table.

Using a sharp scalpel, Erin Schaeffer, a graduate student at the University of Minnesota, cut a slit about an inch long in the muskie’s white underbelly. The slit complete, she took a hydro-acoustic transmitter - about the size of a tube of lipstick - and pushed it through the slit she had just carved.

She wasted no motion. She was in and out of that fish in three minutes and 36 seconds from incision to tag insertion to three closing stitches.

Schaeffer performed her surgery on a cool May morning in a Minnesota Department of Natural Resources boat tied up at the Rice’s Point boat ramp below the Blatnik Bridge. The Minnesota and Wisconsin Departments of Natural Resources are working with Schaeffer on this project to better understand the movements and feeding habits of muskies in the St. Louis River estuary.

“We want to see if they’re using the restored habitat in the St. Louis River and if they’re migrating to Lake Superior, especially the big fish,” Schaeffer said.

Forty hydro-acoustic receivers are already in place throughout the estuary and in Lake Superior, said Jeramy Pinkerton, a Minnesota DNR fisheries specialist at French River. Schaeffer and the DNR crews have surgically implanted the hydro-acoustic “tags” in 60 muskies on the river this spring.

“When a fish passes within about 400 meters of a receiver, it’ll ‘ping’ to that receiver,” Pinkerton said.

Some of the receivers are located in the Duluth Ship Canal and a few are in Lake Superior, so biologists can track muskie movements in and out of the estuary.

At least one 53-inch muskie is swimming in the river, Pinkerton said. That was the longest muskie captured in this spring’s netting. The heaviest was a 48-pounder that was about 50 inches long, he said. About one-third of the muskies were 40-45 inches long.

Curt Ellestad, president of the Lake Superior chapter of Muskies Inc., said this study is important. Many muskie anglers have had difficulty, after the flood of 2012, finding muskies in the river. That storm washed out much of the vegetation where anglers had previously caught muskies.

“Nobody really knows, including the DNR, what the muskies do all summer. Do they come in to spawn and go back to Lake Superior?” Ellestad said. “Where the guys used to fish, pre-flood, those fish aren’t there anymore. This will tell us where the fish are, where they’re going, and also tell us how many fish are in the river.”

Several members of Muskies Inc. assisted the two states’ DNRs and Schaeffer in the tagging effort this spring. The club, along with the Twin Cities chapter of Muskies Inc., also contributed more than $15,000 to the effort, Ellestad said.

This project is similar to one started last year with lake sturgeon in the estuary. A total of 45 hydro-acoustic tags were implanted in sturgeon last year, and another 55 this year, Pinkerton said. The hydro-acoustic receivers in the estuary will receive signals from both the sturgeon and the muskies.

To collect muskies for the hydro-acoustic tagging this spring, trap nets were placed near shore at various places up and down the estuary. A long lead net steers fish to the trap net, where the fish enter a funnel-shaped portion of the net. Once inside a larger net enclosure, it’s difficult for the fish to swim back out through the funnel.

In addition to Schaeffer’s work placing hydro-acoustic tags in the muskies, DNR biologists also are inserting internal tags in the fish to identify them. When a fish swims past a receiver and leaves its ‘ping,’ researchers will know exactly which fish it was, Pinkerton said.  All muskies received a tag with a number unique to that fish. Each of the hydro-acoustic tags have an individual number as well. That number is recorded on the receiver.

Some 250 muskies were tagged this spring as part of a population-monitoring effort, but only 60 received the hydro-acoustic tags.

The hydro-acoustic tags in muskies will send signals for five years. Those implanted in sturgeon will last 10 years.

“The study is kind of cutting-edge, as it is the first of its kind to document the extent of an individual muskie’s use of available aquatic habitats in the St. Louis River and Lake Superior,” said Paul Piszczek, Wisconsin DNR fisheries biologist in Superior. “The resource agencies and anglers can infer how Lake Superior contributes to the success of the fishery. A data gap exists between the river and the lake, and this study will help fill that gap.”

The muskie project should benefit anglers, Schaeffer said.

“Anglers are seeing less muskies,” she said. “We want to get a better idea of what the population is and what habitat they’re using.”

Muskies were native to the river, Pinkerton said, but were thought to be extirpated, mostly due to overfishing, habitat destruction and pollution.

The Wisconsin and Minnesota DNRs have been stocking muskies in the river since 1983 to re-establish the population. The agencies stopped stocking in 2005, and have been monitoring natural reproduction since.

Anglers won’t see most of the hydro-acoustic receivers placed in the river, because they’re too deep, Pinkerton said. However, a few of the receivers have been placed in water about 5 feet deep, he said. Those receivers are marked with white buoys that have a band of black tape around them.

Cost of the hydro-acoustic tagging project is about $113,000, Pinkerton said. Of that, about $86 is from a Minnesota Sea Grant grant, and the remainder is in-kind funds from the Minnesota DNR and the University of Minnesota.

Biologists trying to determine river’s muskie population

In addition to placing acoustic transmitters in muskies this spring, fisheries biologists also are doing an assessment of the muskie population in the St. Louis River estuary. The Minnesota and Wisconsin Departments of Natural Resources are cooperating in the population assessment.

The agencies want to know whether St. Louis River muskies are doing well enough to sustain their population without further stocking, said Deserae Hendrickson, DNR area fisheries supervisor at French River.

In doing the population assessment this year, fisheries officials captured about 250 muskies through trap-netting and placed identifying tags in them. Muskie anglers cooperating with the DNR will keep track of the number of muskies they catch with and without tags this summer, said Jeramy Pinkerton, Minnesota DNR fisheries specialist at French River.

The DNRs will trap-net muskies again next spring for another recapture event, Pinkerton said.

By determining the ratio of tagged fish in the recapture effort to the number originally tagged, biologists can make an estimate of the total muskie population.

Muskie anglers have said that in a few years before and following the 2012 flood, muskies were hard to find in the river.

“There were some habitat changes as a result of the flood,” Hendrickson said. “Places that (anglers) typically caught fish, they weren’t catching them. Whether the fish behavior changed or they weren’t there, we don’t know. Maybe a larger percentage of them went out into Lake Superior to feed.”

The population assessment will give biologists - and anglers - a sense of how many muskies are present in the river.

Netting of muskies for the population assessment was done at several locations in the estuary this spring. Despite the off-and-on cold weather, biologists say it has gone well.

Muskies were first stocked in the St. Louis River estuary in 1983 by the Wisconsin DNR. Both Wisconsin and Minnesota DNRs stocked the species almost annually through 2005. Since then, the agencies have taken a break from stocking to see if muskies are successfully reproducing on their own.

“We’ve seen natural reproduction - young-of-the-year muskies - every time we’ve looked since 2005,” Hendrickson said.