North Dakota Outdoors/ Doug Leier: Fall surveys help fisheries managers measure reproduction, stocking success

In the spring, fisheries biologists have a small window of time to collect the northern pike and walleye eggs that eventually are stocked in North Dakota lakes as fingerlings in May and June.

In the fall, those same biologists revisit many of the waters where fish are stocked to see how those fingerlings are faring.

Scott Gangl, fisheries management section leader for the North Dakota Game and Fish Department, shared some insight into fall fish reproduction surveys in a recent edition of “Outdoors Online,” the Game and Fish weekly webcast.

“Our biologists sample a lot of our lakes around the state looking for young-of-the-year fish; fish that were either stocked or reproduced this year,” Gangl said, “and it gives us an index of how well those stockings took … how well those fish survived into the fall or whether there was any natural reproduction on some fish species.”

Angler use is a factor in determining which lakes are surveyed, Gangl said, as biologists can’t get to all of the more than 400 lakes in one year.

“Some of our heavily fished lakes are a priority, because this information really factors into what they're stocking next year, what their plans are for the future,” he said. “Or they might have a new lake that they just stocked for the first time this year.

“We like to see how well our stocking success is from this year. It tells us, did we have a really good year class? Was there good survival?” he said. “Or if we know that there's good survival this year, we might be able to take a year off next year. Or if we know that there's good survival on a new walleye fishery, we can kind of monitor how fast those fish are growing.”

Anglers are always interested in the reproduction/stocking success on the state’s “Big 3” fishing waters – Lake Sakakawea, Devils Lake and Lake Oahe/Missouri River. Here’s a preliminary assessment of those waters.

“It looks like Sakakawea might have a fairly good number of walleye out there. I haven't seen information on the other species yet, but we had high water this summer and I think conditions in Sakakawea were pretty good for a lot of fish.”

“It looks like their young-of-the-year walleye catches were pretty much close to the long-term average. The downside to Devils Lake, they're not seeing much for young-of-the-year perch, and we could use a perch year-class up there.”

“The one good-bad thing that they found is fairly good numbers of (naturally produced) young-of-the-year walleye (on Oahe). And I say ‘good-bad’ because everybody likes walleye, right, but there's not a lot of forage in Lake Oahe. … I think anglers who fish Lake Oahe are probably familiar with the fact that there's a lot of smaller fish in the system. They have been there for a few years and they're not growing. We don't need another year-class of walleye out there right now, but it looks like there might be one coming up.”

Leier is an outreach biologist for the North Dakota Game and Fish Department. Reach him at dleier@nd.gov.