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Harvesting Large Fish


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A recent study by the Scripps Institution of Oceanography details great harm to fish populations and genetics by the harvesting of large, mature fish.

 

See article at http://news.yahoo.com/s/nm/20080416/sc_nm/...Kw761BdBBAhANEA

 

The DNR sets many of its fishing regulations toward keeping large, mature and genetically successful fish. There are numerous examples of this, most notably LaSalle Lakes regulation for Largemouth or Smallmouth bass of an 18 inch minimum length limit, Lake Bloomington's 15 inch minimum length limit, Lake Michigan's 21 inch minimum length limit, Powerton lakes 18 inch minimum length limit etc.

 

Most regulations protect young, small, immature fish. The fish that don't reproduce or may not have the successful genetic potential of the large, mature fish.

 

The Alliance has a club position on catch and release but in light of this study do we press the DNR, Forest Preserve Districts, and Park Districts to set regulations against the harvesting of mature, successful fish and shift the harvesting of fish to small immature fish? Not everyone is an Alliance member who follows a catch and release ethic. Should the Alliance consider this an important conservation step to protect against the ecological-evolutionary consequences of the harvest of mature, genetically successful fish?

 

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A recent study by the Scripps Institution of Oceanography details great harm to fish populations and genetics by the harvesting of large, mature fish.

 

See article at http://news.yahoo.com/s/nm/20080416/sc_nm/...Kw761BdBBAhANEA

 

The DNR sets many of its fishing regulations toward keeping large, mature and genetically successful fish. There are numerous examples of this, most notably LaSalle Lakes regulation for Largemouth or Smallmouth bass of an 18 inch minimum length limit, Lake Bloomington's 15 inch minimum length limit, Lake Michigan's 21 inch minimum length limit, Powerton lakes 18 inch minimum length limit etc.

 

Most regulations protect young, small, immature fish. The fish that don't reproduce or may not have the successful genetic potential of the large, mature fish.

 

The Alliance has a club position on catch and release but in light of this study do we press the DNR, Forest Preserve Districts, and Park Districts to set regulations against the harvesting of mature, successful fish and shift the harvesting of fish to small immature fish? Not everyone is an Alliance member who follows a catch and release ethic. Should the Alliance consider this an important conservation step to protect against the ecological-evolutionary consequences of the harvest of mature, genetically successful fish?

 

Don't consider myself very knowledgeable on this subject but am trying. I read somewhere that "old" mature fish stop reproducing at some point and are actually a drain on the available resources. Any truth to that? If true, it seems that the minimum length should be at the uppermost range of growth for that particular body of water.

 

-jim

 

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Kevin,

 

Years ago I had a publication from the DNR on Smallmouth growth rates in Illinois which has been tossed to make room in the file cabinet. If my memory serves me correctly, not that many smallies grow to 16-18 " lengths or larger. Most will die naturally before reaching that stage. My own personal beliefs are that these larger fish possess better genetics and should be returned to produce more of the same stock. I'm sure that stream size and habitat also plays a role in overall size as well. I have heard that the larger fish produce fewer eggs but at what stage reproduction stops, I have no idea. Perhaps Someone at the DNR can help out in this area. Policy changes should only be implemented after the science is in.

 

Mike D

 

Not PHD Mike

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  • 1 month later...
Kevin,

 

I have heard that the larger fish produce fewer eggs but at what stage reproduction stops, I have no idea. Perhaps Someone at the DNR can help out in this area. Policy changes should only be implemented after the science is in.

 

Mike D

 

Not PHD Mike

 

I read somewhere that "old" mature fish stop reproducing at some point and are actually a drain on the available resources. Any truth to that?

 

Interesting thread. I tend to agree that size regulations are somewhat upside down. Slot limits often make more biological sense than minimum limits. Maximum size limits might make better sense still but the fishing public would rebel against the idea altogether.

 

In productive streams like the ones we have in Illinois, I doubt we have to worry much about the resources larger smallmouth are taking. The relative number of big fish compared to small ones tends to be low. Also, once they stop growing, fish consume less food and in general the overall relationship between fish size and egg production is positive.

 

I would be pretty surprised if we had streams with so many old fish that the population suffers. Larger fish are in better condition in the spring, tend to produce a larger, higher quality egg with more fat resources and better fry condition. Larger males attract big females, build bigger nests that contain more eggs and presumably produce more young (although males lose growth from the energy they spend defending their nests so they don't usually live very long or reach trophy size).

 

Bigger is usually better.

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Tim

 

Are the genetics of larger specimens of a species different from the other specimens in the system, even though they they are of the same strain? Would these genetics then be passed down through successful spawning in a given system?

 

I hope I am clear on what I am asking. :unsure:

 

The reason I ask is because of a recent experience in Wisconsin when we witnessed anglers legally harvesting large, prespawn/spawning smallmouth. Our minimum argument is to at least close the season to protect these bass through the breeding season. It was difficult to watch 4 and 5 pound smallmouth being tossed in the grass or in buckets, full of spawn, even though it was legal. We were told by the DNR that the legislators thought process is the bass are a renewable resource, so they didn't have a problem with anglers taking the large and vulnerable bass out of the system, since small bass would grow into bigger bass someday to replace them. Do all bass have the potential to grow to trophy size, assuming conditions are favorable, or is there a genetic factor involved? BTW, the CPO as well as the department did not agree with the lawmakers.

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Large body size promotes fitness and survival for a lot of different reasons. There are breeding programs all over the US that believe big fish are "better" genetically. I accept that idea in a statistical sense, but there are probably specific examples where it doesn't hold true.

 

Large smallmouth bass may have simple differences with other bass. Simple behavioral differences (still driven by genetics) may affect them. They may be cautious enough to live long or aggressive enough to grow fast (or just the right mixture in between) or maybe they delayed reproduction and got big instead of making lots of eggs.

 

As far as fishing off spawning beds...if you want a robust smallmouth fishery, you especially want to conserve aggressive dads on the nest. Aggression and risk-taking are genetic traits in largemouth bass and other species and almost certainly in smallmouth as well. Studies have shown that aggressive smallmouth males make better dads when guarding the nest. They defend their fry more actively, allowing more of them survive. Unfortunately, aggressive fish fare worse in a hook and line fishery. They get caught over and over, pulling them off their nests and increasing the chances that someone will finally take them home or kill them with a hook wound.

 

As usual, I'd take the DNR's side rather than the legislators. It sounds like the Wisconsin legislature either doesn't care about smallmouth or they haven't thought about sustainable harvest.

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Thanks Tim.

 

I wrote my post at work (might have even been on the phone when I was typing!). I wanted to add a couple more thoughts, though I believe you got the gist.

 

I may have been a little unclear to those reading this post when I stated the "large and vunerable bass" being taken out of the system. Their vulnerability was because of being in the spawning stage, not because of size.

 

Anyway, I have heard the "trophy fish representing the best of stock" theory as well. If a best of stock theory has any validity, then it would be important to protect these bass and their offspring from fishing pressure during this period. One theory the CPO offered was there is pressure from resort and guiding businesses on the legislators to maintain their right to give their customers what they want (catching lots of big fish) rather than protect the future of the fishery. There was also a reference made to some individuals reasoning that "this is how we've always done it". The bass are still showing up every spring (for now), so how do your change that perspective? Somewhat frustrating to say the least. I believe in an angler's right to harvest within the legal limits. It just seems that the laws may need some realistic updating to protect these bass during the spawn.

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