Inbreeding Fish to Death

Hatchery trout being restocked in Pennsylvania.

It turns out that it's not just dogs, cows and chickens that suffer deficiencies when inbred. So too do fish. As Scientific American reports:

Plummeting numbers of several salmon and trout species have conservationists looking more and more to hatcheries — where fish are reared in comfortable captivity and then released into natural bodies of water. But this strategy may hurt wild populations, according to a paper published this week in Biology Letters.

Researchers at Oregon State University (O.S.U.) found that not only do hatchery-raised steelhead—a Pacific trout sharing the same genus, Oncorhynchus, as salmon—produce relatively fewer and weaker offspring once back in a natural environment, but so do their wild-born spawn....

....Araki and his colleagues looked at the Hood River steelhead supplementation program in Oregon and found that trout fry raised by two hatchery-reared parents had just 37 percent of the reproductive success of those with two wild-born parents, even though both sets of offspring were born in wild waters. If the fry had a mix of one wild and one hatchery-raised parent, then it had 87 percent of a pure-bred wild fry’s reproductive fitness.

Scientists are studying the issue, and are not certain the cause for the decline in fecundity, but inbreeding depression in hatchery stock is strongly suspected.
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