Learning what fish do in their natural environment long has been a focus of fisheries biologists and science-minded anglers alike, and the findings from an ongoing tagging and telemetry study involving U.S. and Canadian research partners are beginning to shed light on the movements of channel catfish in the Red River Basin.

Oddly enough, the two research techniques tell very different stories-at least to this point, said Henry Hansen, a University of Nebraska-Lincoln student researcher who recently published his master's thesis, "Implications of Channel Catfish Movement in an Internationally Managed System."

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Bottom line, channel catfish fitted with special tags inserted near their dorsal fins as part of what's known as a "mark and recapture" study have shown a knack for moving upstream. In Grand Forks alone, local catfish guide Brad Durick has reported clients catching and releasing more than 60 catfish tagged near Selkirk, Man., more than 250 river miles away.

Based on tag returns, or "recaptures," about 30 percent of the tagged, or "marked," catfish reported caught in the U.S. initially were tagged in Canada, Hansen said.

By comparison, catfish surgically implanted with acoustic transmitters seem to favor moving downstream or staying close to where they were fitted with the transmitters, early findings show.

That was unexpected, said Hansen, who gave a presentation on his research during the recent Minnesota and Dakota Chapters of the American Fisheries Society meeting in Fargo.

Hansen also received the Best Student Presentation award at the meeting.

"There was a lot of downstream movement, and what really surprised me was that we saw fish (with transmitters) move from the Red River all the way over to the Winnipeg River," said Hansen, a Mora, Minn., native who worked on the Canadian and U.S. portions of the Red in 2017 and 2018. "We did not expect fish to be jumping tributaries to (Lake Winnipeg). We expected maybe some fish would go to the lake and then maybe move back into the river for spawning and feeding during the summer months."

About 40 percent of the fish with transmitters also moved into Lake Winnipeg at least once during the study, he said.

About the study

As part of the study, which began in 2012, UNL students and faculty adviser Mark Pegg worked with project partners over the next few summers to tag some 16,000 catfish, mostly on the Canadian side of the Red River. In 2016, the project expanded to include the implanting of acoustic transmitters in about 160 catfish, mainly on the Canadian stretch of the river but also in about 40 cats along the U.S. portion of the Red.

A series of 250 "listening stations" anchored to the bottom of the river from Fargo into the north basin of Lake Winnipeg pick up the signals from fish implanted with the transmitters, Pegg said. Each transmitter has a unique frequency and beeps at the listening station when the fish swims by, he said, also recording the date and time.

Data from the listening stations then is downloaded once a year, allowing researchers to track the travels of specific fish. Pegg downloads data from the stations along the U.S. side of the river, while Canadian researchers handle the Manitoba receivers.

Canada's Department of Fisheries and Oceans, a primary partner in the project, also is tracking other species, including walleyes, bigmouth buffalo and sturgeon, Pegg said, but Hansen's research focused on catfish.

The transmitters, which last about five years, cost about $300 each.

"It's been a pretty awesome collaboration," said Pegg, who first met Canadian biologists in 2010 at a conference that set the stage for the research project. "DFO has a lot of resources in terms of the equipment that became available, so it was just kind of the perfect alignment of all things coming together at the right time."

Population scenarios

Besides tracking catfish, Hansen in his research used a series of computer models to gauge the potential impacts of various harvest scenarios on catfish populations based on the extent of those movements.

Considering stable recruitment, or fish from a given year's hatch that are added to the population, the takeaway message is that catfish could be susceptible to overharvest, he says.

That could have implications in Lake Winnipeg, which has an extensive commercial fishing industry, should the netters ever put more focus on harvesting catfish. That, in turn, could compromise the Manitoba stretch of the Red River's reputation as a destination for trophy catfish. Anglers in Manitoba are required to release all catfish longer than 24 inches, but nets don't have that restriction, and there is no harvest quota.

"If we have stable recruitment regardless of where those fish are coming from, and we have a consistent number of fish coming in every year for harvesting, we wouldn't necessarily see less fish, but the quality of fish would go down with very little fishing pressure-especially in the region where exploitation is taking place," Hansen said. "So, for example, if commercial fishing were to take place in Lake Winnipeg, you're not necessarily going to see a decrease in the number of fish if recruitment is stable, but the trophy fishery might start going away in the lake.

"Your number of mature fish might start going away, and that might start spilling over in the lower Red River. And if you have a bad year for recruitment and on top of that have exploitation, that can really start affecting other reaches (of river). Especially when movement is taking place in the system."

More info needed

Still to be determined is whether the differences in documented movements for catfish fitted with tags and catfish with transmitters is a trend or just a blip. River flows and levels generally have been low since 2016, when researchers first began implanting the transmitters, which could account for the general lack of upstream movement.

By comparison, high flows were commonplace during the first few years of tagging.

"There's definitely some head scratching going on with that" disparity, Pegg said. "A big difference is we have almost seven years of tagging data and only 1½ years of telemetry. Once we get more time under our belts from telemetry, we may see a more complete picture."

Given the amount of snow on the landscape and forecasts for spring flooding, there undoubtedly will be plenty of flow along the Red River this spring. That, in turn, could trigger more fish with transmitters to head upstream.

"By sort of an unfortunate luck of the draw, we've had different flow regimes between the two projects," Pegg said. "We'll take it all with a grain of salt until we see the full circle come around for the telemetry. We'll see what that does (with higher flows)."

With his work on the Red River complete and his master's thesis published, Hansen this week heads to Germany, where he'll be working with researchers studying northern pike near the Baltic Sea. Working on the Red River was a dream come true, he says, providing the opportunity to work with fisheries experts from multiple agencies on both sides of the border.

Besides the Canadian Department of Fisheries and Oceans and the University of Nebraska-Lincoln, partners in the project include the Minnesota Department of Natural Resources, the North Dakota Game and Fish Department, Manitoba Sustainable Development and the Manitoba-based Fish Futures organization.

"It's been an incredible experience working for an international team of researchers," Hansen said. "It's a multimillion dollar project where at the end of it, I've walked away with a greater appreciation of what scientists have to do to try to investigate certain topics. But I'm also one of the few people in the world who's probably traveled almost every river mile from Fargo to the north basin of Lake Winnipeg.

"Experiences like that are, in my opinion, life changing."