Are Hatcheries Helping, or Hurting, Wild Fish Populations?

A spawning steelhead trout works its way up the Lewis River at Lucia Falls near Vancouver, WA. (Credit: Greg Shields/Flickr) The Columbia River basin, stretching from Idaho down through Washington and Oregon, is dotted with more than 200 hatcheries in which salmon and steelhead trout are raised before being released to supplement wild populations. Those wild fish have struggled on their own, due to fishing, dams that block migration routes and other human-related pressures. Hatcheries can help stabilize populations, allowing fishing operations to continue, but only if they produce fish whose offspring can thrive in the wild. Michael Blouin, a biology professor at Oregon State University, has long known that fish raised in the concrete troughs of a hatchery are different than wild fish. Blouin and his fellow researchers discovered this back in 2011. Their 19-year examination of steelhead trout — an anadromous fish in the same genus as Pacific salmon — found that steelhead raised in captivity were adapting to the evolutionary pressures of the hatcheries within a single generation. The steelhead that best adapted to hatcheries did worst, in terms of reproductive success, once they were released into the wild. Just how far they were diverging from their wild-born parents wasn’t clear until this month. Blouin and his team published new findings this month that revealed hundreds of genes were being expressed differently due to growing up in hatchery conditions. They counted 723 genes that were expressed differently between fish born from two wild parents and fish born from two hatchery-raised parents. “The study provides further, dramatic evidence that hatchery fish are very different in their adaptations than fish of wild origin,” says Peter Moyle, a fisheries biologist at University of California-Davis who was not involved in the research.