2018 DNR Survey Process
Fish population surveys
Beginning soon after ice out, the Wisconsin DNR will be starting a fish survey on your lake. The survey will begin with fyke netting to mark walleyes and other gamefish. Fyke nets are large trap-style nets that are set along the shoreline in walleye spawning areas. They are checked and emptied once a day. All gamefish will receive a clip on one of the fins, with about half of a fin removed. The fin will grow back in about a year, but the mark will still be visible as a distinct bend in the fin rays. Netting continues until a sufficient number of walleyes are marked.
The netting period will be immediately followed by two nights of electrofishing along the shoreline. Electrofishing works by putting an electrical field in the water to temporarily stun any fish within about 4 feet of the boat, allowing them to be scooped up in dip nets and later released.
Fish marked in the nets will provide a known number of marked walleyes swimming around in the lake. From the electrofishing run, the ratio of marked to unmarked fish will be used to estimate the population. For example, if 1,000 walleye are given a left-ventral fin clip, 500 are captured during electrofishing, and 200 of these have the fin clip, then the estimated population = 1000 X 500/200 = 2,500 walleye.
Additional sampling will be done later as the water warms up. Fyke nets will be re-set to gather data on muskies in their spawning areas, and more electrofishing runs will be done to collect information on bass.
Finally, additional electrofishing runs will be done in the fall as water temperatures cool. These are intended to mainly target young walleyes to assess the amount of reproduction that occurred this year.
Creel Survey
In addition to the netting and electrofishing surveys, a nine-month angler creel survey will be conducted throughout the gamefish season excluding the month of November. Creel surveys are conducted by creel clerks who work all weekend days, most holidays, and randomly-selected weekdays. Shift times each day, either early or late, are also selected at random.
The clerks will conduct counts of anglers to determine fishing pressure on the lake and also record biological information on harvested fish: fish species, length, and finclips. This is used to characterize what anglers are harvesting, and the finclip information is used to calculate the percent of the adult walleye population that is harvested over the course of the season, known as the “exploitation” rate.
The information gained is useful for determining fishery management strategies and evaluating the effects of various management actions like regulations and stocking. The walleye sport harvest and exploitation information is critical to assure that the total harvest of adult walleyes, after tribal harvest is added in, does not exceed a safe level. Thirty-five percent is considered to be the maximum safe level of exploitation that an adult walleye population can sustain. The estimates of catch and harvest from this subsample of lakes can also be used to make projections of catch and harvest over broader geographic areas.
The full results of all of the surveys will not be available until July of the next year, but any preliminary results will be made available as soon as possible. In the meantime, feel free to talk to the DNR staff working on the lakes. They’ll be glad to update you on what they’re seeing.
We appreciate your cooperation with our creel survey clerks.
http://dnr.wi.gov/topic/Fishing/north/trtysprngsrvys.html