DNR Fisheries Management – Max H. Wolter

In 2017, DNR Fisheries Management will be conducting an estimate of the total number of walleye in Nelson Lake. Generating this kind of estimate is useful for evaluating stocking success, setting harvest limits, and adjusting regulations, if needed. The process is commonly referred to as a “mark-recapture” survey. The first step is to set nets on the lake to capture spawning walleye. The nets do not harm the fish, but rather they trap them by creating an area that they can swim into but cannot find their way out (similar to a large minnow trap). Each day, DNR crews empty the fish out of the nets. Each fish is measured, the sex of the fish is determined, and the fish is given a “mark”. In the case of Nelson Lake in 2017, the mark was right ventral fin clip (one of the fins on the belly of the fish). Don’t worry, the fish does not experience pain from this clip and can still swim effectively, it’s similar to clipping a fingernail. The fin will regrow typically within a month or two.
The fish are all then released back into the lake.

The next step is an electrofishing survey that is conducted a few days later. This year, the shocking survey was conducted on April 11th, if you saw lights out on the lake that night it was likely us. The entire shoreline of the lake is surveyed with 5 total electrofishing boats. Each captured walleye is then examined to see if it had a clip or not. The relative proportion of clipped to unclipped fish is then put into an equation that generates the total population size along with “confidence intervals”. This estimate, and the corresponding confidence intervals, are used to set safe harvest levels for both tribal and sport fishing anglers. Complete data from the survey will be available this summer, but there were a few notable catches. We were able to recapture a lot of clipped walleye, which is great for estimating population size, but not a great indicator of a large population. We did see a few of the clipped suckers stocked by NLA over the last two years. I’ll have a more detailed summary of that at the June meeting. And we got a smallmouth bass! Our surveys indicate that smallmouth are exceptionally rare in Nelson Lake so we were very excited to see this lone smallmouth. It was captured near the mouth of the Totagatic River.

Another electrofishing survey will be conducted a few weeks later when the water temperature warms up more. This survey targets bass and bluegill and allows us to make comparisons of how those populations have changed over time and how they stack up to other lakes. We will be very interested to see how largemouth bass have responded to the “no minimum length limit” regulation that has been in place for a number of years.

Throughout the summer a creel survey will be conducted on Nelson Lake. The main creel clerk is from Hayward and his name is Matt. He’s a veteran at doing these kinds of surveys. If he stops you on the water please be cooperative and friendly and Matt will return the favor. His goal is to get the data we need and get you back to fishing as soon as possible. The data collected as a part of this survey is invaluable to understanding the fishery and managing the lake.

The results of all these efforts will be complied into a report that will be distributed to NLA and posted to the DNR website.

– Max H. Wolter
Fisheries Biologist
Hayward Service Center
Bureau of Fisheries Management