Cal Vanize wrote:

Your argument is wrong.

The reason why hatchery fish aren't the same as "wild" is that weaker
fish, even with "wild" genes may be able to survive in a hatchery when
they would not in the wild. It also means that they might not build up
defenses against diseases or be as strong as those having to survive in
the wild.

This doesn't change their genes, only their physical conditioning.

Producing hatchery fish -- even ones bred from wild stock -- doesn't
change the genes, but it does change the gene pool. Hatchery conditions
and natural wild conditions exert two radically different kinds of
selection, obviously. Even if you begin with a genetically pure wild
stock, by the time the fish are released from the hatchery you can
expect the frequencies of various genes in the population to be very
different from the frequencies in a wild population.

For example, suppose there's a parasite in the wild that kills 20% of
the fry, and that there's a genetically based susceptibility to the
parasite. Some fish succumb to it and some are resistant, depending at
least partly on their genotypes. If the parasite is carefully kept out
of the hatchery this selective pressure will be absent, and the gene
pool of the hatchery fish will be different from that of the wild fish.

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