Originally Posted by
prister
Some good discussion on regulations so far, but let me throw in some angler attitude facts and biology. As for bass, the trend we see is actually too much catch and release. Now don't throw tomatoes at me for that comment. But here is the problem. A typical creel survey on KY Lake shows that only 23% of the harvestable size bass (> 15 inches) are harvested. So right now, 77% of the legal bass caught, are released. The bass fishery can withstand greater harvest than that. By removing a few more bass, allows the others to grow bigger. The smaller the body of water the truer that statement is. Think of the fishery like the economy; supply and demand. The supply of shad (forage) versus the demand (bass wanting to eat). We have a great abundance of shad in the lake, which supports an excellent bass fishery. Could it be better if we released more bass? Probably not. You also have to factor in growth season and genetics. The lakes have the potential to produce the occasional 10 pounds, and periodically an 11 pounder. With the data we collect, when there are large year classes their average growth will be a little slower, as compared to a year class with less fish. So, it is ok to harvest a bass. But that is not to say catch and release has not helped. It has. I might sound like a politician on that issue; going both ways. But, anglers should not be scared that keeping a limit of bass on an occasion is going to crash the population.
As for crappie in comparison, creel survey data indicates only 4% of the harvestable (>10 inches) crappie that are caught, are released. The exploitation study (tagging study, 2003) that we did indicated that harvest mortality was around 41%. So for every 100 crappie we tagged, 41 were caught. But then you have to factor in that some anglers did not send in their tags (reporting error), some tagged fish lost their tag (tag loss) and a few tagged crappie might have died (tagging mortality); so then harvest mortality could be as high as 74%. Similar results were seen in a study conducted in 1988, before the 10 inch size limit. This is high for fishing mortality, but the opposite of this, which would be bad, is to have high natural mortality. High natural mortality would suggest that regulations are too protective and therefore the crappie are just dying of old age. Like at Lake Weiss, fishing mortality in 1991 was estimated at 34%, while total annual mortality was 73%. Fishing mortality accounted for only 20% of the annual mortality. Therefore at that time, their study suggested that harvest restrictions were not warranted. Now that is a 20 year old study I reference, so things may have changed since then at Lake Weiss. That just happen to be a research paper I had read. At KY Lake, we have high harvest mortality and good growth, which indicates we need harvest restrictions, which we have. If we went with a higher size limit, our harvest mortality would go down, and natural mortality would go up. Crappie are short lived fish. Old age for a crappie would be around 5 or 6, though we see some up to age 10. However, in last years sample, crappie 12 inches in length ranged between 3 and 9 years old (average is age 5). So you can see genetics also plays a role in fish growth. We have aged some 15 inch crappie, and they were 8 years old. The crappie are sexually mature at age 2, and the 10 inch size limit is protecting crappie to age 3 and 4. So, most will get off 1, if not 2, spawns before being harvestable size. Yes, protecting them a few more years might make sense, but the biology does not support it. Reducing the limit during March –May, also makes sense, but makes enforcement and regulations more difficult. I wish regulations were a simple process, but to change a regulation due to governmental bureaucracy, takes almost 2 fishing season. If we felt a reduction in creel was needed, we would do it across the board for the whole year. But we are not to that point yet. Should we reduce the limit to 10? It might help. But this process of fishing regulation sometimes seems to be 10% biology and 90% angler attitude. It is a balancing act. We have to manage the population for sustainable yield, while keeping the angler happy and buying a license. You have to think, at what point does the limit have to be reduce, for you to say the limited number of fish is no longer worth the cost of a license. So then you give up fishing, or at least buying a license.
Here is another study to supports my theory about crappie at KY and Barkley lakes. Every few years there could potentially be a good year class due to population densities; however you then have to factor in environmental conditions that affect spawns. In other words, just because you have a lot of spawning potential (lots of adult fish in population) does not mean you will have strong year classes. Actually, having moderate spawning potential should produce stronger year classes, if spawning conditions are favorable (water level not fluctuating and no cold fronts).
Can. J. Fish. Aquat. Sci. 58(3): 594–601 (2001) | doi:10.1139/cjfas-58-3-594 | © 2001 NRC Canada
Quasi-cycles in crappie populations are forced by interactions among population characteristics and environment
Micheal S. Allen and Leandro E. Miranda
Abstract: Crappie (Pomoxis spp.) populations have been characterized as cyclic, with strong year-classes recurring at 2- to 4-year intervals. We evaluated the potential for cyclic trends in crappie populations using a population model that included a density-dependent stock recruitment function and random environmental variation. Slow, medium, and fast growth were simulated over 100 years. The model predicted highly variable recruitment that was strongly influenced by environmental fluctuation at low and intermediate stock densities. At high stock density, recruitment was low, even if environmental conditions were favorable. Significant quasi-cycles occurred, but they were not sustained throughout the time series due to random environmental fluctuation. Quasi-cycles occurred because intermediate stock density and favorable environmental conditions occasionally combined to produce a very strong year-class that greatly increased stock density in the following 1–3 years and produced low recruitment, even if environmental conditions were favorable. Empirical data from 32 years of sampling age-0 crappies at Ross Barnett Reservoir showed trends similar to the simulated fluctuations. We conclude that crappie populations likely do not exhibit true cycles but may show quasi-cycles as a result of the interaction between random fluctuations in environment and density-dependent mechanisms. The frequency of such quasi-cycles may be enhanced by rapid growth and high exploitation.
