Efforts to restore lake sturgeon populations in the Red River Basin are going well, and Minnesota Department of Natural Resources fisheries personnel are finding additional evidence of natural reproduction as they work to learn more about the species.
The DNR discovered the first reproductively mature female sturgeon in the Red River Basin in 2019, and crews sampled two more this spring for a confirmed total of three, said Nick Kludt, Red River fisheries specialist for the DNR in Detroit Lakes, Minn.
“That’s really the exciting part of all this,” Kludt said. “The fact that we are beginning to find sexually mature females, that really is the big take-home for me. They’re starting to show up right on schedule when we expected them to start to show up.”
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Using stock from the Rainy River on the Minnesota-Ontario border, the DNR began stocking juvenile lake sturgeon in the Otter Tail River and other Red River tributaries in 1997 in an effort to reintroduce the species to the Red River Basin. Lake sturgeon were common throughout the basin until the early 1900s, when the construction of dams that blocked access to key spawning habitat and pollution resulting from settlement of the Red River Valley decimated their numbers.
In 2002, the DNR began stocking lake sturgeon even more aggressively throughout the Red River Basin, Kludt said, using eggs collected by the Rainy River First Nations in Ontario. These are now hatched and raised to fingerling size at the Valley City National Fish Hatchery in North Dakota.
The DNR, U.S. Fish and Wildlife Service and White Earth Nation Natural Resources Department have collaborated on the effort, Kludt said, and the Red Lake Nation’s tribal DNR also began stocking lake sturgeon in Red Lake in 2007.
This spring’s survey work had three objectives, Kludt said: to implant additional acoustic telemetry tags and smaller, cheaper PIT – short for Passive Integrated Transponder – tags in sturgeon to learn more about their movements and habitat use within the basin; to look for sexually mature or actively spawning female sturgeon; and to continue ongoing tagging efforts along the Otter Tail River, particularly below Otter Tail Lake Dam.
Dam modification projects to accommodate fish passage are planned over the next four years on the Otter Tail Lake outlet, Rush Lake and Little Pine and Big Pine lakes, Kludt said. This year's sampling effort focused on those sites, he said.
“We wanted to get a lot of tags in the system below those barriers, so then we could assess upstream movement post-project,” Kludt said. “It will be a phased approach where Big Pine and Little Pine will be one phase and then Rush-Otter Tail will be the other phase.”
Similar to other dam work on the mainstem Red River and elsewhere in the basin, the modification projects will feature rock-arch rapids that still function as dams but also accommodate fish passage.
“We need fish passage there, but we also don’t want to alter the lake levels,” Kludt said.
This spring, Kludt and other personnel from the DNR’s area fisheries office in Detroit Lakes sampled 102 lake sturgeon during 2½ weeks of survey work that began the second week of May and continued through the month.
The survey ended earlier than planned because of unseasonably hot weather.
Of the sturgeon sampled, 52 were positively identified as males because they were squirting milt, Kludt said, and 48 were of unknown sex that could have been immature males or females. The two reproductively mature females brought the total to 102.
Unless they’re actively spawning, it’s nearly impossible to tell males from females without surgically checking, Kludt said.
The first sexually mature female the crew sampled this spring was a 53-inch sturgeon they discovered with ripe eggs while surgically implanting an acoustic transmitter.
Kludt described the female as an “F4,” meaning she had black eggs and could spawn if she encountered the proper water temperature cues.
Sturgeon don’t reach reproductive maturity until age 15 or so and then only spawn every four to six years; their eggs are black when ripe.
The female sturgeon was captured on Deer Lake in Otter Tail County and released below Orwell Dam on the Otter Tail River after the transmitter was implanted, Kludt said. The second reproductively mature female measured “just shy of 55 inches” and was releasing her eggs, a stage referred to as “F5.”
She was sampled and released below the Otter Tail Lake outlet dam, which is a few miles upstream from Deer Lake, Kludt said.
“That was really exciting because that was a female that was in the system spawning that we captured and were able to verify an attempt at natural reproduction going on,” Kludt said.
The biggest sturgeon sampled during the survey was a 56.7-inch male, he said. Crews also noted six “recaptures” of sturgeon that had been previously tagged.
“Two of those had been tagged upstream near Big Pine (Lake) dam near Perham but were detected down below Otter Tail Lake Dam,” Kludt said. “And then the remainder of those recaptures from previous years had been tagged below Otter Tail Lake dam and then were recaptured there.”
None of the six recaptured fish were able to move upstream from below the barriers where they were tagged, Kludt said.
“Six fish is a small sample size, I will readily admit,” he said. “But again, it just underscores the importance of this dam removal program that we have. There is homing within lake sturgeon populations, so if we have fish that are successfully spawning at a location and then they disperse downstream over a barrier, most data points to the fact that they are going to have a very difficult time getting back to that spawning habitat.”
Sturgeon populations now have recovered to the point where the DNR offers a catch-and-release season throughout the Red River Basin. Fishing has been very good, at times, in recent years, especially on the Otter Tail River.
Anglers also are encouraged to report tagged sturgeon on the DNR website at mndnr.gov and then typing “tagged fish” in the search window. All of the tagged sturgeon, whether stocked by the DNR or one of the tribes, are tied into a central database that allows anglers to learn about where and when they were tagged, Kludt said.
The prospect of a trophy sturgeon fishery in the Red River Basin is exciting, Kludt says.
“If you caught, say, a 50-inch muskie, that’s an old fish, that’s a rare fish and that’s a red-letter day in the life of an angler,” he said. “In the Red River, if you catch a 50-inch lake sturgeon right now, you’re catching a fish that is just edging toward its upper teenage years toward 20 years old and has potentially 60 years of life and growth yet to go.”
Ultimately, Kludt said, the goal is to learn enough about sturgeon movements and habitat use within the Red River Basin to establish an effective sampling program and someday, perhaps, even offer a limited harvest season.
“That’s years and years in the future, but being able to have that sort of fishery within our area on this side of the state, which is part of their native range, (think about) just how exciting that would be, what a benefit to local economies that would be,” Kludt said. “And just how neat that we were able to bring back that species to a place where it had been but then was lost.”
Tagging by the numbers
The Minnesota Department of Natural Resources and partnering provincial and tribal agencies have fitted sturgeon in the Red River Basin with a combination of acoustic transmitters, PIT (Passive Integrated Transponder) tags and “dangler” tags, which are the yellow tags anglers sometimes see attached near the rear dorsal fin, in an effort to learn more about fish movements.
Here’s a look at the number of tags that have been inserted or implanted in lake sturgeon by tag type.
Acoustic transmitters: 19, in addition to 44 Canadian lake sturgeon fitted with transmitters in 2016 and 2017.
PIT: 484 to date, including 436 since 2018.
Project partners also have “marked” other fish species with surgically implanted acoustic transmitters throughout the Red River Basin and into Lake Winnipeg. Some 250 “listening stations” anchored on the bottom of rivers or lakes in the study area pick up the frequencies emitted by the transmitters. Each transmitter emits a unique frequency, which allows researchers to follow the movements of specific fish when the data is downloaded.
In addition to 63 lake sturgeon (19 in the U.S. and 44 in Manitoba), other species acoustically tagged include 80 bigmouth buffalo, 161 channel catfish, 40 common carp, 357 walleyes, 81 freshwater drum and 21 burbot. That adds up to 803 fish in the Red River system that have been acoustically tagged since 2016.
– Brad Dokken