Researchers seek answers to Missouri River fishery decline after 2011 flood

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Biologists are continuing to tag and track walleye and sauger in the Missouri River and Lewis and Clark Lake between Fort Randall and Gavins Point dams as part of an effort to understand declines in the fishery following historic flooding in 2011.

Since 2021, 201 fish have been tagged in the river and reservoir as part of a study of fish movement. The fish sport metal jaw tags, but also have acoustic transmitters implanted in their abdomens. Fifteen receivers spaced every 5 miles throughout the system record any fish that passes within a half mile. So far, 44 fish have been caught and 39 harvested. Two fish have been caught three times.

Biologists hope to use this information to help determine why fish has declined in the reservoir since 2011, when months of high flows flushed many fish through the Gavins Point dam. The loss included emerald shiners, the primary forage base in the reservoir, which hasn't recovered. Neither have walleye, despite more than 100 million fry and fingerlings being stocked since 2014.

Will Radigan, the University of Nebraska-­­­­­Lincoln graduate student doing the field work for the project, said so far the study has shown about 25% of the nearly 200 tagged fish are moving less than a mile, while 10% have moved more than 60. One fish tagged in May 2022 below Fort Randall dam moved 66 miles downstream to Gavins Point dam by September, turned around and went back upstream and was caught in April near where it was tagged.

Two walleye and two sauger have passed through Gavins Point Dam, a fact that is suspected to be part of the issue facing the fishery. Radigan is also sampling larval fish in the spillway below the dam and has found during peak entrainment, more than 20,000 fish per hour pass through the dam. More than 90% are freshwater drum, which is now the primary forage base in the reservoir, but walleye and sauger are also moving through the dam.

Biologists used nets, electrofishing and hook and line to catch a sampling of fish from different reaches of the river, reservoir and the delta at its upper end. They even enlisted the help of Mike Hamsa of Yutan, a fishing guide with The Walleye Guys, who helped catch 56 fish to tag.

A few more fish will be tagged next spring, and tracking will continue through 2025.

Jaw tags are stamped with a three-digit number. Anglers catching these fish are asked to call the conservation agency in their state to report the tag number. If they harvest the fish, they are asked to recover the transmitter and return it as well.

In Nebraska, anglers should report tag numbers to the Northeast District Office in Norfolk at 402-370-3373.

Partners on this research project include the Nebraska Game and Parks Commission, South Dakota Game, Fish & Parks, and the University of Nebraska-Lincoln School of Natural Resources.