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Wisconsin's Great Panfish Experiment

It probably would not surprise you that panfish (Bluegill, crappie, sunfish, and Yellow Perch) are the most sought after fishes in Wisconsin and many other states. Sure, Walleye, bass, and musky are more "glamorous" but who among us does not love panfish? For most of us, a Bluegill or some other panfish were the first fish we caught. I still love catching panfish - whether on my fly rod or spinning tackle. They are abundant, they generally bite readily, and for their size, they give a good fight, particularly on tackle scaled to their size. They are, quite simply, great fishes, well worth our time and effort!

Source: https://dnr.wi.gov/topic/fishing/documents/outreach/PanfishManagementPlan.pdf


The name "panfish" certainly implies that they are meant to be eaten and that has been the history of panfishing. Panfish regulations have been liberal - high bag limits, no size limits, and year-round seasons. Until somewhat recently, the limit was set at 50 fish and later cut to the current 25 fish limit. However, evidence suggests that 25 panfish is creating overharvest and a reduction in the size of panfish over time.

Source: https://dnr.wi.gov/topic/fishing/documents/outreach/PanfishManagementPlan.pdf


Wisconsin has been conducting a pretty significant panfish experiment - an adaptive management study. I LOVE experiments. The idea behind adaptive management is that you try a management strategy, assess what the results are, and then "tweak" the strategy based on the results. Or keep things as is, if that is what the results tell you to do - but you keep monitoring the effects and adjust management if that is what is needed. Some refer to it as "trial and error management" but that really is not a great descriptor. More accurately, it is trial and improvement - management by incremental changes. Essentially, evolutionary principles are used.


In the case of panfish, they are trying to figure out if we can change the size structure of panfish populations by reducing the harvest and/or implementing size limits? Can panfish anglers keep fewer larger fish and will that result in a more desirable fishery?

Source: https://dnr.wi.gov/topic/fishing/documents/outreach/AdapManPanfishPlan.pdf


To be sure, the state's anglers were not clamoring for changes to the panfish regulations. Over 65% of respondents preferred the current 25 panfish bag limit and as the proposed regulations decreased the number of panfish that could be kept, anglers opinions dropped quite significantly. A bit less than 8% of anglers approved of the 5 panfish limit. But, to their credit, Wisconsin anglers were up for trying the great panfish experiment.

Anglers have, in general, been reluctant to embrace size limit reductions. Rypel points out that the limit reductions may actually result in more meat harvested. That may seem counterintuitive, but it’s true. “As bluegills get bigger in length, they get exponentially bigger in weight,” he says. “So if you catch a few larger bluegills, you often get more meat than if you caught a bunch of smaller ones.”

Source: https://blog.nature.org/science/2015/10/15/why-everything-you-know-bluegill-management-wrong-fish-fisheries-panfish-fishing/


This may be the selling point. Harvest fewer fish - and have to fillet fewer fish - and get the same amount or more meat for the pan (or deep fryer). It will be interesting to see what the results of the experiment are, how they "tweak" the regulations, and maybe most importantly, how will anglers respond to the regulations? Will anglers be willing to change their view of panfishing? If the science leads us in this direction, will anglers follow? That really is the "great panfish experiment" in a nutshell.

Source: https://dnr.wi.gov/topic/fishing/documents/outreach/PanfishFactSheetMay15.pdf


A bit of fish biology - the generalized equation to estimate the weight of a fish is W = aL^b where a is the Y-intercept and b is the slope and W is weight and L is length. The slope is a number around 3 which means that the length is cubed and has a huge impact on the weight of a fish. This means that as length increases, small increases result in MUCH greater increases in weight. A 6.5 inch Bluegill averages 0.19 pounds, a 7.5 inch Bluegill averages 0.30 pounds, and an 8.5 inch Bluegill averages 0.44 pounds - nearly half again heavier than a fish one inch shorter! (Schneider et al. 2020)


Preliminary evidence is that it is working. Bluegill maximum size increased by a half-inch and average size increased by nearly an inch (0.8 inches; source). Additionally, Rypel (2015) found that the time that the regulation was in place was important in the increase in average size. In other words, the longer the regulation has been in place, the larger the increase in average Bluegill size.

Source: https://dnr.wi.gov/topic/fishing/documents/outreach/AdapManPanfishPlan.pdf


The proposed regulations in the first part of the study essentially allow 5 or 10 of any one species to be harvested and the seasonal regulation protects panfishes during May and June when fishing pressure is high and their susceptibility tends to be very high. In particular, nest guarding male Bluegill which are typically at least 6 to 8 years old are most vulnerable during their spawning period. I know one of my most fantastic days with a fly rod in hand was for Bluegill spawning in less than a foot of water where catching them on a foam spider was fast and furious. And I out-fished everyone 3 to 1 or more because the fly rod was able to set the fly down so much more gently than a spinning rod and a casting bubble could. I am not terribly proud in saying that I kept 25 nice large male Bluegills. But our thinking about panfish and harvest is changing. What we thought we knew about panfish management is probably wrong (source) and quite possibly, times are changing.


It is an interesting experiment and so far, it seems to be working. How will anglers respond to the regulations? Do we - can we - apply the regulations more broadly if they do work and are accepted by anglers? And if we do, will anglers be willing to have more - or even all - lakes with more restrictive regulations? It is one thing to change the regulations on a relatively small number of lakes and allow anglers to chose over lakes with less restrictive regulations. It will be interesting to see what happens with the experiment and how the experiment is applied to the rest of the state's lakes.


Applications to Trout


Honestly, I do not know that there are any. I know it sounds sort of counter-intuitive but panfishes are longer-lived than are trout (for the most part). Parental (nest guarding) male Bluegills are typically 6-8 years old before they spawn for the first time. Few stream trout make it to 4, let alone 6 or 8 years old. This is the old r-selected / K-selected continuum. r-selected species have high potential rates of population growth and they tend to grow fast but do not live long. K-selected species tend to have fewer offspring, are more likely to care for them, and generally their populations do not grow as fast. Panfishes, fall more on the K-selected end of the compared to trout. For trout, survival to a relatively old age and large size is a rarity. For panfishes, it is less of a rarity. Different life histories for different fishes.


References:


https://blog.nature.org/science/2015/10/15/why-everything-you-know-bluegill-management-wrong-fish-fisheries-panfish-fishing/

https://dnr.wi.gov/topic/fishing/documents/outreach/PanfishManagementPlan.pdf

https://dnr.wi.gov/topic/fishing/documents/outreach/AdapManPanfishPlan.pdf

https://dnr.wi.gov/topic/fishing/documents/outreach/PanfishFactSheetMay15.pdf


Rypel, A.L. 2015. Effects of a Reduced Daily Bag Limit on Bluegill Size Structure in Wisconsin Lakes. North American Journal of Fisheries Management 35:388–397.

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