Sorry, I've been outta the country for a few days, will try and catch up here. Not to pick on anyone, but there are alot of misconceptions regarding population genetics that are important to clear up in the discussions here. I'll start with a quote from Fishbadger:
Quote:
Much has been discussed aptly on this site about the problems with introducing fish populations with different genomes into native populations. In my opinion, one of the worst effects is crossbreeding of hatchery fish with native fish, resulting in the introduction of hatchery clone (non Broodstock, mind you) genetic material into the native gene pools. This is called introgression, and results in dilution of native genetic makeup. One could view this as another mechanism of genetic drift (which is good from a natural selective standpoint), but I'd disagree in that it is completely artificial and accelerated, and results in loss of native genomes and hence everything that makes the nates special. The concept of introgression was a theoretic one, and if I remember correctly, has been shown to have occured in certain salmonid populations in low gradient river systems like the lower Snohomish, with statistical significance. Once those unique populations are lost, they can never be recovered (it is an extinction). I reviewed the literature on this about 7 years ago for a talk, but I don't have the references handy. I might be able to find them with a lot of work somehow.
First of all, even under the worst cases of hatchery management, there is little in the published genetics literature to suggest that hatchery stocks are anything near homozygous "clones" as you call them. In fact, recent findings using DNA markers (not the ancient protein electrophoretic ones) suggest that hatchery breeding practices can easily maintain or capitalize on existing genetic variation and often demonstrate high levels of heterozygosity. Secondly, your wording indicates a clear confusion regarding population genetics terminology (whether it be human or otherwise). Random genetic drift is very different than "introgression" (BTW the population genetics term for introgression is migration), with drift not being related at all to crossing among or between populations, but is instead the random changes in gene frequency that occur normally in small populations. In fact your statement that genetic drift is a good thing from a natural selective standpoint makes absolutely no sense at all! Drift and selection are opposing forces, tending to maintain balance in populations. As for effects of migration (introgression), there are many examples of straying in natural steelhead populations. It is an important part of all salmonid biology. In fact, coastal Oregon populations show remarkable levels of straying, even to the point that fish will leave streams they have entered, head back to the ocean, and be later found spawning in systems miles away. It is a proven, natural way of maintaining balance in gene pools.

In conservation genetics literature, particulary as it relates to aquatic systems, intraspecific hybridization is often cited as a threat to the "genetic integrity" of rare native species. But what is genetic integrity, and how do we know it when we see it? Lately, the term seems to be used by scientists and laypersons alike as little more than a euphanism for genetic purity. In reality, there are great difficulties in applying these definitions in wild systems. I have, and continue, to propose that genetic integrity should have a strong functional component, and that it be determined case-by-case. There are recent good examples in the literature, particularly with amphibians.

Another misconception that appears through this thread (sorry to pick on you again, fishbadger) was seen in the following stqatement:

" You cite a statement that “Genetic diversity
in salmon and steelhead populations is extensive, and within-population diversity usually exceeds the diversity that exists between populations.” How do you support that statement regarding degree of diversity? I agree with Geoduck up there. It sounds backwards to me. Do you have any of your own material here? Sounds like there is a teleprompter nearby."

I'll respond to this one. In fact, there are many examples that show intrapopulation genetic variation to be higher than interpopulation variation. This has been shown in native populations of frogs (Scribner, et al. in Molecular Biology and Evolution 11(5):787), humans (YES HUMANS, you should know this one; Da Silva et al Am J Phys Anth 109:425, trees (Kara et al Silvae Genetica 46:2-3:155). That's just the ones directly at my fingertips, there are lots of others. For fish it is less clear, but a recent study of natural populations in Alaska (Olson et al Trans. AFS 133(2):476) show low interpopulation diversity and high intrapopulation diversity in chum salmon, while the opposite was true for coho. This suggests that no one approach will work for each species, and assessment of genetic variation must be done for each species under study.


I agree that the recent issues on Vancouver Island suggest that the health of our salmonid stocks are far beyond a hatchery or non-hatchery issue. We simply don't know enough to restrict our options at this point.

Lastly, why did Geoduck not respond to the chromosome numbers issue? I think that the chromosome numbers especially demonstrate that there could possibly be only a few large metapopulations.

I'll get outta the way here and await the shotgun blasts.