Biologists search for clues on why fish population has declined in Lewis & Clark Lake after 2011 flood

LINCOLN, Nebraska — Nebraska and South Dakota fisheries biologists are studying why fish populations have declined in popular Lewis & Clark Lake since the flooding of 2011.

Populations of emerald shiners — the primary forage fish in the Missouri River reservoir — haven’t recovered, and neither have walleye, despite more than 100 million fry and fingerlings being stocked there since 2014.

So biologists with the game commissions in both states, along with a student from the University of Nebraska-Lincoln, continue to tag and track walleye and sauger in the Missouri River between Fort Randall and Gavins Point Dams, in Lewis and Clark Lake and in the Missouri River below Yankton.

Biologists even enlisted the help of Mike Hamsa of Yutan, a fishing guide, who helped catch 56 fish to tag.

Since 2021, 201 fish have been tagged 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 five miles along the river record any fish that passes within a half mile.

So far, 44 of the tagged fish have been caught and 39 harvested. Two fish have been caught three times.

Will Radigan, a University of Nebraska-­­­­­Lincoln graduate student, is doing the field work for the project. One of his findings is that some fish are moving through Gavins Point Dam, which might help explain the drop in fish population.

Many fish were washed through the dam during the flooding of 2011, washing away many forage fish that sustain sport fish like walleye.

During peak sampling, it was discovered that more than 20,000 fish and larval fish per hour pass through the dam, though more than 90% were freshwater drum.

Anglers catching tagged 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. In South Dakota, anglers may call the Game, Fish and Parks office in Chamberlain at (605) 734-4548 or go online to https://gfp.sd.gov/forms/fishtag/.