Lake Koshkonong System - Slot or Not?

Lake Koshkonong System - Slot or Not?

There’s been quite a bit of buzz the last few years in regards to enacting a slot limit on Rock River/Lake Koshkonong system. The fact that’s occurring is a good thing; it shows many anglers care deeply about the future of this fishery. Anyone who has fished Lake Koshkonong system for any number of years has seen the up and down cycle of the walleye population and size. What’s concerning to many of these anglers is the bigger fish population appears to be going down. Not only are they seeing it, data and surveys obtain by the DNR also supports this finding. So that brings us as a group to a crossroad. What changes can be implemented that will better protect walleyes and also appeal to most anglers?

There actually are a few options to look at. Enacting a slot limit is the option getting the most attention, but if we look deeper into this, it may not be a good option right now. Let me explain. I’ve had the opportunity to sit down with DNR fishery managers and pick their brains on this topic. Along with discussing Lake Koshkonong’s fishery, I was able to view data obtain over the years from both netting surveys and shocking surveys. What stuck out the most was the huge inconsistent walleye spawning and stocking survival numbers. The fishery managers stated from their experience, in order for a slot to work, a system needs to have consistently higher numbers of natural or stocked “replacement” fish coming back into a system.

So how do we know how many new walleyes are coming into a system? The DNR conducts a “Young of the Year” survey annually to analyze the previous spring walleye spawn. Crews travel “X” amount of miles in a boat and use a boom shocking device to count the number of walleye hatched that spring. (Large fish are not part of this data). Once crews complete their time on the water, they calculate how many walleye per mile they found. Past data, which is listed in the table below, shows that these numbers are all over the board. Some years have a great survival rate, however many are quite low. As one can see, this data supports the inconsistent spawning behavior seen on the Rock River/ Lake Koshkonong system. For a slot limit to work as intended, this up and down cycle must be balanced first.


“Young of the Year” reporting data from 2002 to 2016

 Year    2002     2003     2004     2005     2006     2007     2008     2009     2010     2011     2012     2013     2014     2015     2016  
 Walleyes / Mile   7 13 55 4 9 20 15 4 7 9 2 104 8 6 20


But slot limits work great on other systems such as the Wisconsin River. True, however using the slot limit success seen on the Wisconsin River/Lake Wisconsin system as an example of what the Rock River/Lake Koshkonong system could become is not a fair comparison for a couple of reasons.

One, the Wisconsin River system is much larger than the Rock River system. The Wisconsin River spans 430 miles and is located entirely within the Wisconsin border. The Rock River spans 299 miles throughout Wisconsin and Illinois, which only about a third is located within the Wisconsin border. So, if we don’t include the Illinois section of the Rock River, we’re comparing a 430 mile system to a system roughly 100 miles long. That’s not exactly apples to apples.

Secondly, the Wisconsin River has awesome spawning habitat locations for walleyes, making for good consistent spawning numbers each year. (Again, a huge factor in slot limit success) The Rock River system is quite opposite. It’s deficient in needed walleye spawning habitat and relies heavily on stocking to help maintain a healthy fishery. Even though stocking is a huge benefit, it too can be inconsistent. For an example, in 2016, the Bark River Fish Hatchery attempts to harvest walleye eggs were unsuccessful for a variety of reasons, but no stocked fish were placed into the Rock River/ Lake Koshkonong system. Although it’s not normal, natural spawn numbers alone can sometimes hold their own. Thankfully this occurred in 2016 when stocking efforts failed and will help bridge potential gaps in walleye populations seen down the road.

So if a slot limit isn’t the way to go right know, what are other options? Changing the size/possession limit to an 18” minimum size and three fish daily possession limit is one choice. This option targets the 15” minimum size and five fish daily possession limit currently in place. Since female walleyes are considered mature at 18”, this change would allow female fish the opportunity to reach spawning potential for at least one season before they can legally be harvested. Allowing more fish to reach maturity and spawn will only help increase natural spawning numbers. The change in possession limit to three fish is pretty obvious. Less fish harvested daily increases survival rates and allows all walleyes a chance to grow.

Another option would be to enact a restricted season of some sort. Completely closing the season like that of other systems is not likely, nor would it be accepted by us as anglers. However, a reduction of the daily possession limit during the spawn (March – May) could be an avenue to pursue. Allowing only a one or two fish daily possession limit during this time would help increase chances of a more successful spawn in an already struggling system.

The third option would be to enact both a size/possession limit change and a restricted season. This would be the most controversial way to go out of the options discussed above, but it would likely increase walleye survival and growth the quickest.

The key to success on the Rock River/Lake Koshkonong system is walleye numbers. We need consistent high numbers to withstand the high pressure and/or we reduce the pressure to help the numbers. Enacting a slot limit at this time will help the fish currently in the 18” to 25” range, but the populations of those fish are small right now. A slot limit does nothing to protect the replacement fish needed for its success. Think of it like this - A slot limit is Step Three. Fixing the numbers first by enacting a size/possession limit or possibly a restricted season change are Steps One and Two. A slot limit may very well be the answer down the road, but let’s set it up for success and not skip the first steps.


Captain Adam Walton
Pike Pole Fishing Guide Service