February 2, 2011

THERE'S NO SUCH THING AS SPECIES:

A Fishy Date: Steelhead and Rainbow Trout Mingle in the Northwest (Nick Neely, 02/01/2011, Audubon)

Anglers know that steelhead aren’t quite like rainbow trout—they’re enormous, reaching up to 55 pounds! But in fact, these ocean-running, rod-debilitating, aquatic gorillas of the Northwest are indeed rainbows, Oncorhynchus mykiss. That some members of this species rove the sea for years and become giants before returning to their birth streams to spawn, while others live quieter, local lives in freshwater, is an enigma. Depending on environmental cues like water temperature and food availability (factors we don’t fully understand), it seems any combination of parents—two trout, two steelhead, or a steelhead and a trout—can produce either form.

Now researchers at Oregon State University have added further intrigue to this mystery by discovering that steelhead and their smaller counterparts mingle (wink, wink) quite a lot: On the Hood River, a tributary to the mighty Columbia, 40 percent of returning steelheads’ genes are derived from rainbow trout, not steelhead parents. “What’s particularly remarkable is the extent to which they interbreed,” says Mark Christie, a fish geneticist and coauthor of the recent study, which appeared in Molecular Ecology.

Posted by Orrin Judd at February 2, 2011 5:49 AM
blog comments powered by Disqus
« THOSE ARE "RETIRE TO SPEND TIME WITH MY FAMILY" NUMBERS: | Main | SEIZING THE MORAL LOW GROUND: »