KEEP OLD PANFISH? - Bob Boese - May 21, 2012
KEEP OLD PANFISH?
First, a little science; fish can be aged by examining scales or various bones (scale exams leave a live specimen). Hard body parts grow as the fish grows, adding annual rings similar to the rings in trees. Under a microfiche reader, panfish scales look a bit like a blend of a fingerprint and a common seashell. Scales get larger as the fish grows by adding to the outside edge. Because fish are cold-blooded and grow very little during winter, a thicker ring is formed, giving a year mark.
Once again, I find myself disagreeing with Mr. Boese. As a scientist myself, with an M.S. in Biology (I minored in Ecology), I am once again appalled at the lack of actual scientific evidence that many 'experts' put forward as fact, all in the name of Political Correctness. As far as "a little science" goes, it's nothing of the kind. A growth chart from the Alabama Co-Op Extension does not constitute a scientific evaluation. It is just an estimate. That's all, and it wouldn't even be relevant for bodies of water in other parts of the country.
A larger fish is not necessarily genetically superior to a more average-sized fish. It's just older, and on top of that, more than likely approaching the end of it's natural life. Leaving all the larger fish can actually hurt the gene pool, because since they have a size advantage, they can run more average-sized fish off from the best breeding areas, meaning less fish will be born, and less will survive. Keeping some of the larger ones allows average fish to have a fighting chance to increase the diversity of the gene pool.
And, large fish do not necessarily spawn large offspring. That only works under a controlled selective breeding situation, which is impossible in the wild. If large fish consistently spawned larger offspring, then panfish, which most species evolved during the Pliocene Period, around 5 million years ago, would be much larger than their fossilized ancestors. Fossil specimens of ancient bluegills are around 8-10"long, on average. So their descendants should weigh around 20 pounds and be a few feet long by now, but they aren't. The size has changed little in 5 million years. It's because genetics doesn't work that way in nature. There are many factors effecting genetics other than just size. Unusually large fish can even be an indicator that all is not well with its genes. An unusually large size usually comes at the expense of something else, just like in other animals. Organisms suffering from gigantism, and acromegaly have a short life-span, and if they can even breed at all, pass undesirable genes along.
The "leave the large fish" crusade is just a PC motto, as far as panfish go. They are in no danger of being wiped out anywhere in their range from over-fishing, and in most places do not get enough fishing pressure. Culling may benefit marginal trout populations to a certain degree, but it has no meaningful effect on panfish populations. They breed at an unbelievable rate, and can over-populate areas if there is not enough predation. So, the best way to keep the panfish populations healthy is actually not to cull your fish (except to release fish that are not legal sized), and just keep what you catch and enjoy them. As long as you do not exceed the legal creel limits, the panfish will be just fine.
I'm not much on PC and don't try to mislead folks, but I try to do homework. Translating hard data into readable articles requires a bit of interpretation and interpolations, and, hopefully, doesn't produce too many mistakes.
I can always be wrong, and maybe I am this time, but I don't think I misunderstood the finding in http://publish.uwo.ca/~bneff/papers/...fe history.pdf, although I might have. What I understood was that sneakers and satellites pass their genetic traits to offspring and their offspring have as good a chance at survival as parentals offspring. Consequently (and this is my extrapolation) a diminished population of parentals (larger fish) means more bluegill with cockholder characterics (smaller size).
Similarly, http://www.pnas.org/content/101/8/2381.full suggests to me that such genetic effects happen in the wild.
A more casually presented site http://hatch.cehd.umn.edu/research/f.../bluegill.html indicates that smaller females produce smaller egg numbers.
And if both genetics and enviornment effect growth patterns http://repository.lib.ncsu.edu/publi...e+history.pdfs it would seem to me that saving larger fish to breed would produce larger future generations.
Other data was also reviewed and led me to the same general conclusion.
The expert in this field (based on studies completed) appears to be B.D.Neff, and I will endeavor to get more of his materials to further evaluate the need for survivorship of larger bluegill.
Sorry if I'm wrong.
Bob, I think I'm trackin with you. While it doesn't necessarily mean that the survivability of the species is enhanced....it can benefit a particular water in the genetic "size" of the fish it supports.
I didn't say you were wrong, Bob. I just disagree with the conclusions, and the methodology. There are advocates on both sides of the issues, and it has been hotly debated for at least a decade or more. The differences that I can see is that the "leave the big fish" group seems to rely mostly on statistical information, from samples taken in the wild. The "keep a random selection" crowd mostly relies upon previous genetic lab research, and experimentation under controlled conditions (a lab or hatchery), where all random elements are removed or accounted for. This is impossible in the wild.
I am of the experimentation and direct observation crowd. Old school, maybe, but for me, if it cannot be duplicated under controlled conditions, then it is not a fact. Experimentation over the last 100 years has shown that size is not necessarily an indicator of superior genetics. For livestock, raised under human control, selection of desirable traits does allow a greater degree of expression in future generations, but that is not always a superior genetic trait. Chickens, for example, have absolutely no chance of survival in the wild, because we have selected them according to preferences, sometimes to the effect that they cannot even walk on their own. They are certainly not genetically superior to their wild cousins. And further experimentation has shown that artificial selection only works in a controlled environment.
As for bluegills, few fisherman would be able to tell if a large fish they have caught is a younger, genetically superior specimen, or just a genetically-average old fish. Odds are, it's just an average old fish. These fish are going to die off soon, most likely within a season or two, making the next younger group the new superior breeding population. However, since the they have been disproportionally targeted, in favor of leaving the large fish, next season will have a lot smaller breeding population, meaning less eggs will be laid, meaning less fish in the long-run. It's shooting yourself in the foot. In my opinion, this defeats the entire purpose of fish management. Harvesting fish equally along the adult size range preserves the genetic diversity that populations need to maintain. Genetic diversity, not artificial culling, is what keeps populations healthy, and in balance.
And, as I said, it can be argued the other way as well. I just prefer to rely on experimental, reproducible data, rather than statistics that change every time they are conducted, depending on when, where and who did them. Any politician will tell you that you can use statistical information to prove any point of view, depending on what kind of spin you put on it. I do believe that statistical information can be useful as additional information, but not as proof of anything, and can only be relied upon very lightly. For science, it is the same as eyewitness testimony in a court of law....somewhat useful, but not enough to convict on its own.
And this is just my opinion, and is certainly not the last word on the subject. One of the things I love most about science is the free and open exchange of differing viewpoints, even with regards to itself, that transcend all national, and social boundaries. Even when we think we have proved something beyond all doubt, such as when we believed dinosaurs were reptilians, new evidence comes along, such as the idea that at least some dinosaurs may have been warm-blooded, that forces us to reopen the issue to attempt to arrive at the truth. I hope it never changes.....
In nature there are to many variables such as food souce, oxygen in the water, optimal water temps and so on which may create a genetically enhanced fish. These fish may appear bigger compared to fish from another area of a pond, stream, river, what have you. I for one cannot tell by looking at a fish whether it is an older fish or just a healthy fish do to nature. Whereas in a lab, you could raise a fish from conception and track growth and age but, if you place the lab fish along side the natural fish, would you be able to tell the age of the natural fish based on comparison? I don't think so.
I love reading this post and hopefully I may learn how to actually age a fish properly
Tags for this Thread