Natural Reproduction Next Goal for Red River Sturgeon

As the Red River Lake Sturgeon Restoration Program closes out the first phase of its efforts in 2021 and 2022 fisheries biologists and staff are eyeing up new goals of establishing natural reproduction for the fish which were once extirpated from the border water between North Dakota and Minnesota. With a reproductively mature population now existing and turning up in the sampling efforts of the Minnesota Department of Natural Resources (DNR) and tribal partner surveys each spring, opening more upstream river miles and the full extent of the Red River from Lake Winnipeg to Wahpeton is a key objective and crucial to the continued presence of these prehistoric fish according to Nick Kludt, DNR Red River Fisheries District Specialist.

The Long Run

"We started stocking them in 2002 as part of our phase one of the reintroduction, and the goal there was mainly to reintroduce fish to the system, and to that end, the DNR focused on lakes – particularly Otter Tail Lake and Detroit Lake," Kludt details of a partnership with tribal agencies which stocked Round, White Earth and Red Lakes with sturgeon in northwestern Minnesota, "as we move into phase two of this restoration, we're really making a move toward natural reproduction, so in 2023 into 2029, we're going to focus more on rivers and cease that lake stocking," he concludes.

A big part of the second phase, which begins after the final stocking of fish in those lakes in 2022, will work on river connectivity restoration to help sturgeon complete their life cycle and spur more natural reproduction, with some limited stocking of lake sturgeon in those rivers. Throughout the 1900s, the installation of lowhead dams on the Red River and its tributaries led to their extirpation from the system as the fish were prevented from moving far upstream in the smaller flows which provided suitable spawning areas. Unable to reproduce in these prime locations, their populations quickly dwindled.

With the fish moving hundreds of miles on an annual basis, the longer they can travel uninterrupted, the better it is for their populations. As a result of this need, the DNR has been hard at work removing dams over the last two decades and replacing them with navigable riffles which sturgeon can swim up to the next section of water. Of the 70 dams on the Minnesota side of the Red River, 44 have been removed since 2002, with plans for further replacement for those remaining structures through 2029. One last dam on the Red River near Drayton is set for demolition and replacement in the fall of 2022 with help from the U.S. Army Corps of Engineers, opening the main trunk of the river from Lake Winnipeg to Wahpeton for fish movement.

"In a lot of cases, we already can move fish from the glacial lakebed segments of the river – your flat Red River valley – up into what we call the beach ridge area, that would be the shoreline of glacial lake Agassiz, where you have higher gradient flow and steeper river slope, and you have a lot more riffles; fast tumbling water that is well oxygenated that flushes out a lot of the sediment and that's going to be that preferred spawning habitat for our lake sturgeon," Kludt explains.

Keeping Track

To survey the populations, the DNR uses electroshock surveying in the upper reaches of the Red River basin to collect lake sturgeon – some currently 50 to 60 inches in length – and place them in a tank on the boat for a return trip to the shore. In 2017, the first sexually mature male fish was found, and in 2019 the first ripe female was discovered beneath Big Pine Dam on the Otter Tail River. Once their specifications are cataloged, they will be marked with a dangler tag, which is attached externally and showcases a number on the yellow plastic placed behind the dorsal fin. This season, fish will also be tagged internally with an injected PIT tag, which is scanned like a chip placed in a hunter's bird dog, for

tracking and surveying in the future. Unique to this year's sampling, a selection of 30 lake sturgeon will also have acoustic telemetry tags surgically implanted into their bodies.

"From roughly the Breckenridge-Wahpeton area all the way up to Lake Winnipeg, the south basin of Lake Winnipeg, and the Winnipeg and the Assiniboine rivers are all covered with acoustic receivers - these are essentially hydrophones that are prepositioned on the river bottom - to listen for these sturgeon as they disburse throughout the system," Kludt explains of the new tracking program which will monitor the outfitted fish in real time, providing instant data on their movement to the agency.

The acoustic telemetry tags last for about six years, providing those monitoring the species with data on how far the fish are moving, where they are stationing in their travels, and where the most ideal habitat and spawning areas might be. With sturgeon being able travelers, the DNR has tracked them on the move throughout the Red River system through less technical means in previous years. One of the longest movements documented during the first phase of the program was from a sturgeon that was tagged in the Otter Tail River near Orwell Dam by Fergus Falls, Minn., which then in the span of a month, exited Loon Narrows into northern Lake Winnipeg, constituting hundreds of river miles traveled in that

short timeframe.

"Those rock arch rapids [are] really good shore fishing sites on the Red River and a lot of anglers who report tagged lake sturgeon are fishing below those," Kludt notes of the sturgeon-friendly lowhead dam replacement structures on the system, adding, "that appears to be excellent sturgeon foraging habitat, because we get tag returns from those locations across the summer."

While similar programs have helped increase populations on the Rainy River along the Minnesota-Canada border to a fishable state and brought back the ancient denizens of Lake Superior to the St. Louis River in northeaster Minnesota, it will likely be several decades before such a fishery is established on the Red River. Female lake sturgeon can live to be 80 to 150 years old, and currently those in the system are young at just 19 years of age at most if they came from the first stockings of the program in 2002. Depending on the water temperatures, agents of the DNR will be looking for more sturgeon that are ready to reproduce in the agency's upcoming surveying efforts. Ideal spawning temperatures for lake sturgeon occur right around 50 degrees, and many sampling sites along the Otter Tail River are only in the low 40s right now. However, Kludt is optimistic that with the previous year off due to Covid concerns, the beginnings of a restored, reproductively mature lake sturgeon population will be more evident in the agency's upcoming sampling efforts in the headwaters of the Red River basin.