Earlier this spring, biologists from North Dakota and South Dakota tagged the last of some 36,000 walleyes that are part of a comprehensive and long-running study on the Missouri River System in the two states.

Since 2013, North Dakota Game and Fish biologists have tagged more than 17,000 of those fish from the Missouri River and upper end of Lake Oahe. The study area extends from Garrison Dam in central North Dakota downstream to Oahe Dam in South Dakota, and involves a major collaboration of biologists and researchers from North Dakota Game and Fish, South Dakota Game, Fish and Parks, and South Dakota State University.

Tagged Walleye

Angling mortality rate that we've seen in the first three years of the study has been about 17-27 percent, depending on the region of Lake Oahe and the Missouri River. (Photo courtesy NDGF)​

"The study is designed to assess walleye movements, mortality and what proportion of the walleye population is harvested annually by anglers," said Paul Bailey, south central district fisheries biologist for North Dakota Game and Fish.

The study targets adult walleye, each fitted with a metal jaw tag stamped with a unique number to identify the fish, and a phone number to report the tag. Anglers can either keep or release the fish. Anglers practicing catch-and-release can write the tag number down and report it, leaving the tag on the fish when released.

In both states, anglers have caught enough tagged walleyes already to provide

biologists with some valuable information. "The angling mortality rate that we've seen in the first three years of the study has been about 17-27 percent, depending on the region of Lake Oahe and the Missouri River that we are in," Bailey said. "Those are all acceptably low rates of mortality that basically says that anglers are not having a negative impact on the fishery at the present time."

In addition, Bailey believes a lot of anglers assume there is a walleye migration that occurs every spring, similar to a spawning run. "The information that we are getting suggests that this really isn't the case," he added. "What anglers are seeing is really an illusion, based on water temperatures."

Movement patterns suggest over half of the tagged walleye that were reported by anglers were caught within 10 miles of where they were tagged and released. However, Bailey said the pattern shows fish tagged in North Dakota moved greater distances than those tagged farther downstream, and North Dakota fish moved both upstream and downstream after tagging.

"The rule is that these fish aren't moving very far, but for every rule there are some exceptions" Bailey said, noting that some fish tagged in the Garrison Dam area were caught near the Oahe Dam more than 200 miles away.

While the tagging portion of the project is now complete, anglers can still report tagged fish as they are caught in the future.

Anglers can report tags by calling the phone number found on tags, which, anglers should note, is a South Dakota phone number. Tag information can also be reported on the North Dakota Game and Fish website, gf.nd.gov, or by calling 701-328-6300.

Anglers should record the date and location of the catch, whether the fish was kept or released, tag number and length and weight (if the fish was measured). Anglers who report tagged fish can keep the tag, and will receive a letter providing some history on the fish.

A small portion of the tags offer a reward to anglers to encourage returns, Bailey said, with these tags clearly marked "Reward."

Continued study and research is important in differentiating between the perceptions and realities of fish movement and mortality on the Missouri River System in the Dakotas.