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Measuring Reproduction, Stocking Success

Article By 
Ron Wilson

Fish Stocking

Scott Gangl (left), Game and Fish Department fisheries management section leader, and Paul Bailey, Department fisheries supervisor, sort, measure and record lengths of yellow perch and walleye caught from a Logan County lake. Fall reproduction survey work occurs annually on dozens of North Dakota waters across the state.

Marvin Miller Lake – located 6.5 miles south, 8 miles west and .5 miles north of Gackle – is off the beaten path. You have to be looking for the 800-acre fishery to find it.

With a wealth of waters in south central North Dakota – some with names, some without, and many that look like the one you just passed – a sign along state highway 34 confirms its location.

First stocked with walleye in 2002, and annually thereafter, this Logan County fishery didn’t really catch the interest of anglers until fall and winter of 2012. By then, the walleye had finally reduced the fathead minnow population to the point that anglers’ baited hooks looked tempting.

“We saw the walleye population building and building, but they weren’t reducing the fathead minnow population,” said Paul Bailey, North Dakota Game and Fish Department district fisheries supervisor.

Things changed when Bailey started doubling the walleye stocking rate for Marvin Miller.

“What I learned at Marvin Miller changed my approach to managing this type of walleye fishery,” Bailey said. “I believe it works better to take an aggressive stocking strategy right from the start. A lot of these prairie lakes won’t be around 10 years down the road.”

The word has been out on Marvin Miller, and a number of other prairie lakes like it, for awhile. “The walleye fishing in May and June was unbelievably good,” Bailey said. “It’s not a secret anymore.”

To predict the future of Marvin Miller Lake, or any other body of water for that matter, is difficult, considering the role an unpredictable Mother Nature can play. Even so, every fall fisheries biologists conduct fall reproduction surveys on all large and mid-sized reservoirs in the state, and many of the smaller waters as well, to see what they can possibly expect in the coming year.


Fall reproduction sampling provides fisheries biologists with an index that measures natural reproduction and stocking success. It allows biologists to see if fish did spawn, and how fingerlings stocked in June survived summer.

“Oftentimes, the biggest hurdle for fish is getting through that first year of life,” said Scott Gangl, Game and Fish Department fisheries management section leader.

Department fisheries personnel have been conducting fall reproduction surveys for decades. Today, with a record number of fisheries in the state, biologists are sampling 30 or more lakes in each of their districts alone. Bailey manages 90-100 waters in his south central district and planned to sample 30 in fall, especially those waters where walleye were introduced this year.

“With so many lakes on the landscape, our biologists try to get to as many as possible,” Gangl said. “As far as sampling goes, our fall reproduction surveys are in the top two or three in terms of tools that we use. We combine the information learned from fall reproduction sampling with a number of other things to determine management goals, stocking requests and plans for the upcoming year.”

Fish Stocking

Scott Gangl releases hundreds of young-of-the-year yellow perch, and the occasional fathead minnow, caught in a single trap net set in Marvin Miller Lake earlier this fall. During the release, Gangl estimates just how many young fish are in the tub.

Gangl said fish stocking requests are made months in advance to help federal fish hatcheries prepare. “Initial stocking requests for 2014, for example, will come in around November,” he said. “District fisheries supervisors may tweak those numbers over winter, depending on the forecast for winterkill in district lakes.”

On September 10, Bailey, Gangl, and Justen Barstad, Department fisheries technician, sampled Marvin Miller Lake, using half-inch mesh gill nets and 3- by 4-foot trap nets, both of which are designed to catch smaller fish.

“The small mesh gill nets are set in deeper water and are well-suited for catching young-of-the-year walleye,” Gangl said. “The traps nets are really good at catching other fish species, like fatheads and yellow perch, which cruise the shallow shorelines.”

With many lakes to pick from in his district, Bailey said one of the reasons he chose to run a fall reproduction survey on Marvin Miller is because of the lake’s importance as a walleye fishery.

“Between the really good walleye population and the angler pressure, we wanted to make sure that we’ve got more walleye on the way,” Bailey said. “Plus, we wanted to see what was happening with the forage population.”

Without crunching the numbers, Bailey said the fall reproduction survey at Marvin Miller suggested that walleye stocking efforts earlier in 2013 were successful.

“Young-of-the-year walleye were fairly abundant and in a few years should be to the size that anglers are interested in,” Bailey said. “Also, there is a good yellow perch population, which will provide forage for walleyes for some time to come.”


Bailey said fall reproduction surveys are more important than ever, considering the advent of 40-plus new walleye lakes in the state in the last decade.

“These surveys let us know where we are having some success in developing these fisheries,” he said.

Fish Stocking 3

Justen Barstad, Game and Fish Department fisheries technician, records the lengths and an estimate of the number of walleye and yellow perch young-of-the-year netted during fall reproduction survey work in September in Logan County.

Fisheries biologists who questioned how a late spring and delayed ice-off would influence fish reproduction in North Dakota waters finally have a few answers.

“Things aren’t looking too bad,” said Scott Gangl, North Dakota Game and Fish Department fisheries management section leader. “We weren’t really sure what to expect. While we aren’t setting records, we are seeing some good reproduction.”

Department fisheries biologists have for years conducted fall reproduction surveys on many of the state’s big and small waters in an effort to gauge natural reproduction and stocking success.

Gangl’s report came with about a week remaining in September. At that time, about 80 percent of the scheduled survey work on selected waters was complete. A more complete report will surface sometime in October, he said.

“One thing to note, our biologists around the state are seeing some pretty good numbers of young-of-the-year yellow perch, signaling some good reproduction this year,” Gangl said. “Perch are fairly early spawners, so it appears they weren’t bothered by the late spring.”

According to early reports, Devils Lake was one of those waters that reported fair to good numbers of young-of-the-year yellow perch.

Earlier reports also indicated good numbers of young walleye in the upper reaches of Lake Sakakawea, and fair to good numbers of perch on the east end.


“Another noteworthy thing on Sakakawea is the number of emerald shiners found in the back part of bays,” Gangl said. “While Sakakawea is not hurting for forage, it’s always nice to see those alternate forms of forage for the lake’s game fish species.”

Lake Oahe, on the other hand, is in need of a forage fish boost after the majority of the rainbow smelt were lost during high water in 2011.

“Our fisheries biologists, thus far, are finding good numbers of white bass in Oahe and some shad,” Gangl said. “This was our second year in a row of stocking shad in Oahe, so it’s nice to see some reproduction.”

On another note, Gangl said fisheries biologists are seeing fair survival of walleye stocked around the state in North Dakota’s smaller waters.

“They’re also seeing fair numbers of young-of-the-year pike,” he said. “While we initially didn’t know what to think of the late spring, it apparently was good for fish.”