Geoduck,
I think I share your concern. However, the thing about market hunting leading to depletions and extinctions is that it wasn't regulated. Banning a practice is one form of regulation. Limiting harvests to a level that can be sustained by a population is a restrictive form of regulation, just not as restrictive as a ban.
Do you really believe that the healthy runs of pink, chum, and sockeye salmon cannot support a harvest? Can a fish population support a sport harvest but not a commercial harvest. Many of us appear to have a pre-conceived notion that sport harvests are lower, and therefore, not harmful to a population, whereas commercial harvests are much larger, and therefore very detrimental to a population, leading to depletion and extinction. This simply isn't true. Overharvest, whatever the method, is just that, overharvest.
If you consider steelhead for a moment, we may have a useful example. I know it's not popular here, and I don't support the idea myself - for other reasons, but the healthiest populations of wild steelhead in WA state on on the coast, and they are subjected to both sport and commercial harvest. OK, but why are wild steelhead populations in SW WA in the tank? No commercial harvest of significance there (excepting the late winters that get whacked by the re-emerging spring chinook gillnet fishery). But SW wild steelhead have been depressed since the early 1990s if not longer. We might say that habitat is degraded, but that's not news; habitat degradation is rampant throughout the state. Besides, you can produce wild salmon and steelhead even from fairly poor habitat, just not as many of them - with fewer or no harvestable surplus, of course.
Try this example: recent recreational ocean harvests off the WA coast have been higher than the commercial harvests. If so, how is it that commercial fishing is inherently worse for those salmon populations than recreational fishing. This seems to support my contention, that the amount of harvest, not the harvest method, is the real issue affecting the health of a fish population.
My point here is that harvest, regardless of whether it is sport or commercial, needs to be regulated so as to achieve necessary spawning escapements. In which case a dead fish IS just as dead whether it is caught commercially or recreationally, and therefore, it is not available to the spawning population.
One last hypothetical example. Fish population X averages a run size of 10,000 fish. We have years of data that indicates a healthy, conservative spawning escapement should number 6,000 fish. That leaves 4,000 fish to be harvested, or not. It's a social and environmental choice, really. If the 4,000 fish are harvested commercially, how is that any more harmful to the population than if the are caught recreationally by hook and line? I can think of "but ifs", however, there should be no functional difference to the sustainability of the population.
Many of us believe in our hearts that commercial fishing, as contrasted to recreational fishing is more detrimental to fish populations, without knowing just what factors are affecting the populations. What you know in your heart is not debatable, but that doesn't make your knowledge right. It's critical thinking, and what you can know in your head, that permits us to understand how systems, like ecosystems, and population dynamics work.
As a personal note, I am picky about what commercially caught salmon I buy, avoiding any that I don't think should be targeted for harvest.
Sincerely,
Salmo g.