Crappie Science in the Headlines By Brian Waldman

Researchers and biologists are always doing studies in order to learn more about what makes our fisheries work, and what at times causes short term problems. Here's a look at some recent research that pertains to our favorite fish, the crappie.




Crappie Anglers: Poler or Troller?


“Trolling May Intensify Exploitation in Crappie Fisheries”


If you're a crappie angler, chances are you're either a poler, a guy that fishes with a single outfit at a time like in bass fishing, or a troller, someone who has multiple lines out, often with multiple baits on each line. One thing that hasn't been taken into great consideration is the ratio of polers to trollers on a given body of water, and whether there are any adverse affects depending on the ratios.



Researchers studied the catch statistics of anglers fishing while trolling with multiple poles (trollers) and those fishing with single poles (polers) in Mississippi reservoirs. They wanted to find out which method caught more fish, if there was a correlation between number of poles used and fish caught, and whether if everybody trolled, could exploitation rates become a detriment to the fishery.

It turned out that on average, the fishery was "equally split between polers and trollers. In spring, 90% of crappie anglers were polers; in summer, 85% of crappie anglers were trollers". As such, the two tended to offset each other over the course of the year. "The size of harvested crappies was similar for the two angler groups, but the catch per hour was almost three times higher for trollers than for polers. Catch rates by trollers were directly correlated to the number of poles fished", although there was a limit to how many. The catch curve flattened out at a certain point, suggesting inefficiency as to how many trolling poles a single angler can handle.

One thing I found very interesting was that "the average harvest rate for one troller fishing with three poles was similar to the harvest rate obtained by one poler". This becomes the breakeven point between the two methods, and just happens to be exactly where Indiana fishery biologists have set the limit as to number of poles allowed to be fished by a single angler at once - good call on their part.

Modeling suggested that a 50/50 mix of polers and trollers (unlimited number of poles) in a fishery works out to be about a 1.3X increase in overall harvest versus a 100% poler fishery. If a fishery becomes a 100% trolling fishery, that exploitation rate increases to 1.7X a polers only fishery. Since most crappie anglers are 'catch-and-keep" anglers, biologists would be wise to take local popularity of crappie methods into account when assessing crappie fisheries and regulations.




Of Crappie and Crappie Minnows

“Seasonal Patterns in White Crappies' Consumption and Growth: Influences of Varying Water Temperatures and Prey Availability”


Everybody wants to catch big crappie, but crappie frequently don't grow very large in some waters. Initial research had pegged water temps as one possible reason why. That research suggested that growth of white crappie will stop when water temperatures exceed 80 degrees. However, this newest research suggests that it's not actually water temperatures that cause the slowed growth in summer, but limited prey availability. Modeling and growth analysis suggested that the fastest growing crappies were ones that had high water temps and plenty of available prey fish as food. When prey fish were limited and crappie had to rely on invertebrates, white crappie often ceased growing or lost weight, even during periods with suitable water temperatures. Which ties in nicely with the following study.


“Risk of Predation, Variation in Dissolved Oxygen, and their Impact upon Habitat Selection Decisions by Fathead Minnow”

When you hit the bait shop to buy "crappie minnows", in most instances you are buying and fishing with a minnow species known as the fathead minnow. Being a very small fish species, it doesn't take a lot of available oxygen for these guys to survive when compared to larger fish, especially larger predators that feed on them. These smaller minnows have learned, and this lab experiment verified, in the presence of a predator to seek refuge in low oxygen environments, which then limits the ability of the predator (in this study, yellow perch) to be in the same habitat and subsequently, diminishes the liklihood of being preyed upon. This is frequently referred to as 'resource partitioning'.

The interesting tie-in between the two studies then becomes one in which even in a body of water where you might have plenty of high energy food (prey fish) living in the same waters, this resource partitioning separates them out sufficiently so that in essence, it acts almost the same as if there wasn't enough food to go around in the first place. A similar theory has recently been proposed relating to walleye and some of their preferred prey fish in certain waters. The point being, it's not often something as simple as having a size limit to ensure larger crappie, because harvest may not be the restrictive problem. Access and availability of suitable high density forage is frequently key.



The Tough Road of Crappie Biologists

“Influence of a modified length and creel limit on the crappie population in a large Illinois reservoir”


Being a biologist isn't easy, especially when it comes to crappie anglers. One subject that constantly gets brought up is why we don't have a size limit on crappie. Seems like crappie anglers are always wanting bigger and better crappie fishing in their lakes. The simple answer is because it largely wouldn't work on most of our waters. Research and modeling suggest you need a population with good to above average growth combined with low natural mortality for them to work well. This is the exact criteria that both Ohio and Pennsylvania have adopted for their crappie programs. Indiana biologists have looked at the stats for a lot of our reservoirs, and to the best of my knowledge, only two bodies of water have been identified that fit the above scenario. Anglers think that you can simply slap a 10" size limit on a lake full of 6"-8" crappie and in a year or two, all those fish will have grown to 10" - WRONG. In many if not most cases, they'll stunt out and the population will be worse off than when you started.

Back on the original point. Biologists over in Illinois (Rend Lake) came up with a creative idea to improve crappie fishing for larger fish while stabilizing the cyclical nature of the population. They took their existing 25 fish limit and applied a tiered bag limit, such that you could only keep 5 of your 25 crappie >10", and the other 20 had to be <10". They later (2004) revised the over 10" component to 10 > 10", with the remaining 15 having to be under 10". This forced harvest of smaller fish while protecting for over harvest of larger fish. From a recent presentation on the results; "The size structure of the crappie population improved noticeably following implementation of the regulation. Data from the fall 2002 trapnet survey showed a sharp rise in the percentage of the crappie population > 10 in and this increase has remained relatively stable for eight years post-implementation. Creel data also showed a dramatic increase in catch rates and harvest of crappie > 10 in."

Sounds like a win for crappie anglers. Some posters on fishing forums even pointed out that it is, at times, difficult to even get your 15 fish under 10". However, the majority of the posters complained that they didn't like the new tiered system, instead arguing that they would just prefer a simple 25 over 10" limit, which as was already mentioned, won't work on a majority of crappie lakes in our region. Some went so far as to call the regulation "stupid".

It just goes to show that there are many facets involved with setting regulations, not the least of which is angler opinion. In this case, even though the fishery probably wouldn't have improved, and maybe even gotten worse, anglers would rather have a simplified creel limit instead of a specialized regulation. Part of this likely stems from the nature of crappie fishermen, that being primarily a catch and harvest type endeavor. Surveys show that not many edible sized crappie get released by anglers. Unlike bass or muskie fishermen who have a very strong catch and release ethic, crappie anglers, along with bluegill and walleye anglers, are more geared toward harvest. As such, any regulations that negatively impact that ability to harvest are frequently met with criticism.