Lake Chippewa Flowage Vacation

I’m pleased to report that after our big spring walleye survey we know a whole lot more about
Chippewa Flowage walleye than we did a few months ago. I referenced this survey in past editions of this newsletter, but this was our once-a-decade estimate of the total number of adult walleye in the Chippewa Flowage.

These “population estimate” surveys are a large undertaking on any waterbody, but on a lake the size of the Chip it’s akin to a small military operation. We had lots of help coordinating and conducting the survey, and I want to acknowledge all the other DNR teams that came from Spooner, Brule, Mercer, Park Falls, Barron, and even Lacrosse and Madison. We also had great collaboration with the Great Lakes Indian Fish and Wildlife Commission and LCO Conservation Department. Many local businesses assisted as well. The Landing and Deer Run offered their boat ramps at a time when ice was blocking most other access points to the lake. Other resorts have been great about allowing our creel clerks to use their grounds to interview anglers (more on that at the end).

Our population estimate is a “mark-recapture” type survey. The first phase of the survey is the “mark”. In this phase we use fyke nets to capture any and all walleye that we are able to and “mark” them with a fin clip (you may catch a fish with one of these fin clips this summer, the fin grows back over time). We started netting in the small open water area near CC bridge on April 24 and caught spawning walleye immediately, even though the rest of the lake was still >90% ice covered. As the ice receded over the following days we expanded the netting operation and brought in more teams to run them all. At our peak we had 80-90 nets in the water and were handling about 3,000 walleye a day. By May 1 we’d captured and “marked” 12,888 different walleye. These are all released back into the lake to mix back into the population.

The second phase is the “recapture”. In this phase we use our electrofishing boats to cover shoreline all throughout the flowage. We selected 97 miles (43% of total shoreline) and conducted the electrofishing surveys over three nights (May 2-4). We capture all walleye we encounter and record whether they had a fin clip or not. It is that ratio of clipped to unclipped fish that can be put into equations to estimate the total number of walleye in the lake. In the electrofishing phase we captured 4,604 walleye, 762 of which had a clipped fin.

If you’ve hung with me this far you must really like fish. And you probably have some questions. I will tryto anticipate those and answer them with the remainder of the article:
So what’s the estimated number of walleye in the Chip?: Our (preliminary) estimate is 72,837 adult
walleye. There are many more juvenile walleye that are not represented in this estimate.
Cool, but how many of those are legal?: We conduct estimates by size class as well. We estimate there are 19,168 walleye between 15-20” and another 904 over 24 inches. So right around 20,000 legal walleye.

What about male:female ratio?: We estimate there are 4.4 males for every 1 female. That is right in line with what we observe in healthy walleye populations.

How does this estimate compare to other points in the flowage’s history?: It might help to convert the big numbers down to per acre estimates for this. Our 2022 estimate was 4.8 adults per acre. The last estimate was done in 2011 and was 3.1 adults/acre. In 1990, the estimate was 5.2 adults/acre. It’s great to see that we have been able to increase abundance since 2011 and are now approaching what was observed in the 90s. Not a lot of lakes can say that right now. Remember, the larger pattern throughout the Midwest is declining walleye abundance.

How does this compare to our shared goals for the fishery?: In the Chippewa Flowage Fishery
Management Plan we set two objectives for walleye: The first was a population with 4-8 adults per acre.

We’re right in the low end of that range with our recent estimate of 4.8/acre. The second objective was to have 20-40% over 15 inches. We estimate that 31% of the flowage walleye are over 15”. The current population is meeting our targets for both abundance and size. That’s not to say things are perfect though! More on that later.

What’s the biggest walleye out there?: We captured a number of walleye between 29.0-29.5 inches,
but we never cracked 29.5 inches. Considering that sample includes around 17,000 total walleye, I can say confidently that walleye larger than 29.5 inches are very rare in the flowage.

Did you get data on other species?: Yes, some. We recorded lengths and tag data on all musky we
captured since we have a lot to learn there. Other species were counted but not measured. That will give us some idea of abundance but not size. With our focus on walleye, we will have less data available for other species this year. We’ll be back to a more wide-ranging focus next year. However, we will do our regular bass and bluegill survey in early June 2022.

Any other surprises?: One thing that was striking was the difference in size structure between the east and the west. The average size of walleye on the east side appears to be about 2 inches smaller than the west side, and gets more extreme the further east and southeast that you head. That means an angling regulation that is a good fit in one area may not be a good fit elsewhere. That will be a management challenge that we will be looking at in the near future.

What happens next?: Technically, this survey is not done. We also have a creel survey component that will provide a lot of fantastic data. That will run through summer and into fall. If you fish often (or are just lucky) you may get stopped by one of our friendly creel clerks. They will ask some questions about what you targeted, what you caught, and how long you were out. If you harvested any fish on that trip they may ask to measure them. Please be cooperative. These data are critically important to managing the fishery and we do not get this opportunity often. Ultimately, we’ll want to use all these data to update our management strategy for walleye and other species. CFAPOA members will be an important part of that conversation.

There’s always more to learn in fish world, I’ll report back soon with more information on the creel
survey and anything else we’ve learned out on the water.

Until then, good luck fishing.