NORTH DAKOTA OUTDOORS MAGAZINE

Marked Fish, Multiple Waters

Ron Wilson

Walleye partially in water held by biologist

A walleye tagging study was started in spring on Devils Lake to gain a deeper understanding of how anglers are utilizing the state’s most sought-after species.

It’s been nearly 20 years since the North Dakota Game and Fish Department initiated a study using marked walleyes on this popular fishery.

Todd Caspers, Department fisheries biologist in Devils Lake, said the aim of the new three-year study is to tag at least 1,000 walleyes each year throughout the lake’s reach.

“The purpose of this study is to estimate the exploitation rate on our walleye, or basically the percentage of the fish that anglers are going to harvest each year,” Caspers said.

While the three-year study at Devils Lake is the state’s longest-running look into a walleye fishery, Department fisheries biologists from around North Dakota earlier in spring initiated one-year walleye tagging studies on six other waters: Lake Addie, Griggs County; Mosher WPA, Barnes County; Horsehead Lake, Kidder County; Davis WPA, Sheridan County; Heart Butte Dam, Grant County; and the Missouri River System from Garrison Dam to Oahe Dam. The latter study is a team effort between the Game and Fish Department and South Dakota Game, Fish and Parks.

“One reason that we conceptualize this multi-lake, multi-year study is to gather information from a wide variety of populations,” said Scott Gangl, Department fisheries management section leader. “So, putting it all together gives us a bigger picture to say whether our statewide regulations are serving our fisheries well over a broader scale than just looking at exploitation on a single lake.”

Caspers said the walleye fitted with metal jaw tags in Devils Lake ranged from 13 to 30-plus inches, or those fish anglers are interested in harvesting for the table or maybe for hanging on the wall.

“We’re running this study on Devils Lake longer than the other fisheries because one year the fishing might be really good and exploitation might be a little higher, and vice versa if it’s a slower year for walleye fishing and exploitation would likely be lower,” Caspers said. “So, in the three years we’ll see that kind of average out to get a better picture of what our exploitation rate is.”

Walleye being released after being tagged

Game and Fish Department fisheries biologist, watches as Jonathon Simak, fisheries seasonal personnel, releases a tagged walleye back into Devils Lake. The walleyes fitted with jaw tags in the three-year study on Devils Lake ranged from 13 to 30-plus inches.

The waters picked for the tagging studies are well-developed walleye fisheries, lakes anglers are likely to target and, in return, report their catches of tagged fish.

“They don’t necessarily have to be lakes that we expect fishing to be really good this year because we want to see the spectrum of exploitation. We want to see the spectrum of fishing quality out there,” Gangl said. “Some of them could be really good, some of them could be a little bit slower and the tag returns will come in a little bit slower.”

What’s certain is that the study waters hold plenty of walleyes.

“We have a good variety of size structures out there … some of the lakes we’re tagging fish are chockfull of eater-sized fish, the 15- to 20-inch walleyes that anglers like to keep,” Gangl said. “And then some of them are maybe top heavy, dominated by bigger fish because people haven’t exploited them very heavily. So, we’re getting a little bit of really cool information on the sizes that anglers prefer to harvest.”

Preliminary findings from other Department tagging studies have shown, Gangl said, the sizes of fish that anglers desire and selectively harvest.

“We see higher release rates on the larger fish, or we see more of the smaller fish being released,” he said. “Most of the fish that we’re tagging are going to be 13 inches and longer, so they’re kind of right at that breaking point where people are going to start harvesting. We don’t have tagged fish that are really small, but we did tag everything above that, so we’ll get a lot of those larger fish that are in the systems too.”

Ignoring fish size for a second, Gangl said the goal for the one-year study lakes was to tag a minimum of 500 walleyes.

“We’ve done some background analysis to say that 500 is the number of fish we need to get good statistical confidence in our data. The numbers could go up from there,” he said. “In spring when biologists are tagging fish is a busy time, but if they’re catching a lot of fish they’ll oftentimes tag more. Once they reach that 500 threshold, everything else on top of that is just going to improve our statistical power.”

When it comes time to report the study fish, fisheries managers want anglers to treat the tagged walleyes just as they would treat any other fish they might have caught. So, if it’s a fish an angler was planning on harvesting, go ahead and harvest that fish. If it’s a fish an angler was planning on releasing, go ahead and release that fish. Just record the tag number and leave the tag on the fish.

Anglers can report any tagged fish they encounter by logging into their North Dakota Game and Fish Department account or use the “tagged fish reporting” feature on the Department’s website at gf.nd.gov.

Like last year, a number of fish in the study lakes have been fitted with metal reward tags.

“We assume that the reward is big enough that anglers are going to 100% turn it in, because not every tag that gets caught is reported to us,” Gangl said. “We need to have some idea of what that reporting rate is so that we can use the bigger data set to meet our needs. That’s just part of the study process.”

Gangl said anglers who catch a fish with a reward tag can present the tag in person at a Game and Fish Department office or simply provide a photograph of the tag on the online reporting site.

While surrounding states have seen lower reporting rates from their anglers, Gangl said, that’s not been the case in North Dakota.

“I have to give a shout out to our anglers because they have always been really good about reporting tags ... they’ve always taken an active role in these studies and we’ve long had really good reporting rates,” Gangl said.

Return to North Dakota Outdoors June 2025 Edition