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| Is there any reason to believe that stocked fish will spawn (or attempt to spawn) under different conditions than naturally reproducing populations?
Thanks,
Brian
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Posts: 32886
Location: Rhinelander, Wisconsin | They will attempt to spawn under whatever circumstances. If the environment is right, they will reproduce, if not, they won't. There's a ton of variables, when Dave or Sorno get some time I'm sure they'll answer. | |
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Posts: 178
| Snowcrest 6 - 4/30/2006 4:06 PM
Is there any reason to believe that stocked fish will spawn (or attempt to spawn) under different conditions than naturally reproducing populations?
DAVE: If stocked fish are the product of several generations of captive broodstock, as was the case with Wisconsin trout until recently, then the most important traits of wild fish can be lost in just a few generations, resulting in stocked fingerlings that cannot compete with wild fish or reproduce successfully in the wild. If, on the other hand, we annually capture broodstock in the wild, as has always been the case with muskellunge in Wisconsin DNR hatcheries, the offspring probably have just as good a chance of spawning successfully (as adults) as any of their cohorts born in the wild. However, problems could occur if we fail to take ENOUGH brood fish from the wild to represent the full range of genetic diversity in our wild populations. If we take too few fish for broodstock, we run the risk of missing some of the rare fish that may be genetically programmed to spawn at different water temperatures or in different habitats. This can lead to a more uniform hatchery product that is not as adaptable to changing conditions in the environment. We want to avoid this uniformity. We want diversity. We want fish of all sizes from different self-sustaining lake populations with various behavioral characteristics in order to maintain a diverse, adaptable, product in our stocked fingerlings. Such fish will have a better chance of "making it" in a world where temperature and habitat are changing, new diseases and invasive species are showing up, etc. That is why you see the Wisconsin DNR changing procedures to rotate among at least 5 different lakes annually to supply wild broodstock to each hatchery; and it is why we have increased the target level from ~10 females to 19-26 females annually (mated with 2-3 different males each) for purposes of collecting and fertilizing eggs for each hatchery rearing muskellunge (Woodruff and Spooner).
Hope that answers your question, Snow...
Dave Neuswanger
Fisheries Team Leader, Upper Chippewa Basin
Wisconsin DNR, Hayward | |
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Posts: 203
Location: Germantown, WI | Snowcrest,
Dave N. gave a pretty thorough answer on the issue of broodstock. Was that really your question or were you thinking more about the issue of why stocked muskies do not seem to reproduce well in many waters outside of their native range? That is the issue that has really intrigued me. While I am not a scientist I have come to the conclusion that muskies have adapted to have fairly narrow spawning habitat requirements. They are not nearly as adaptable when stocked into new waters as some species are. For example, largemouth bass can seemingly spawn and thrive just about anywhere. This is clearly not so with muskies. That is why they must be stocked Southern WI, IL, IN, OH, and PA to maintain fishable populations. There is obviously more to it than that, but it seems clear that stocking muskies in less than ideal habitat or disturbing their habitat in native musky lakes has a profoundly negative effect on musky reproduction. I'm sure that in some waters there is probably reproduction, but not enough to offset predation with the result that there is very little recruitment of fry to adults.
Muskies are a native fish to Pennsylvania, my home state, but now are maintained almost entirely through stocking. Why is that? The main reason is probably habitat loss. Muskies were historically found in the Ohio River drainage, especially the Allegheny River, its tributaries and natural lakes that drained into the Allegheny River. If you look at those rivers, they were dammed for navigation and then polluted, dredged and developed. Many of those rivers have recoverd and are now producing good fishing for a variety of gamefish, but they may never recover suitable musky habitat such that stocking can be discontinued. If you look at some of the natural lakes that drain into the Allegheny River which once contained native muskies such as Conneaut Lake, Edinboro Lake, Sugar Lake, and Lake LeBoeuf you could point to extensive shoreline development, the draining of marshes, and the damming the lakes for water stabilization (which elimated fish passage to and from the Allegheny and its tributaries) as major negative impacts.
Most of the reservoirs in the midwest that have been stocked with muskies such as Kincaid, Shelbyville, Webster, Leesville, Piedmont, Pymatuning, Arthur, etc do not have any significant natural reproduction taking place. All are dependent on stocking. It could be a combination of factors leading to poor reproduction/recruitment including broodstock issues, habitat issues and predation, but the bottom line is that those fisheries are dependent on stocking. Also it seems that there is no reason to believe that these waters will ever have naturally sustained musky populations. That is why we should be so diligent to protect and preserve the naturally sustained musky lakes in MN, WI, MI, Ontario and elsewhere.
Tom Ramsey
member Milwaukee Chapter Muskies Inc | |
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spawning among natural populations versus stocked fish