Here’s another surprise from the unpredictable frontlines of biology. A new study from Oregon State University finds that steelhead trout raised in hatcheries face a dramatic and unexpectedly rapid drop in their ability to reproduce in the wild—nearly 40 percent per captive-reared generation. Fish reared in a hatchery for two generations had around half the reproductive fitness of fish reared for a single generation. The effects appear to be genetic, and probably result from evolutionary pressures that quickly select for characteristics that are favored in the safe, placid world of the hatchery, but not in the comparatively hostile natural environment. The study, to be published Friday in the journal Science, raises serious questions about what happens to wild populations when they interbreed with hatchery fish, and the wisdom of many hatchery practices.
Julia Whitty is Mother Jones’ environmental correspondent. You can read from her new book, “The Fragile Edge,” and other writings, here.