Salmon born in captivity become domesticated in as little as one generation, a new study finds, explaining why hatchery-born fish don't do as well as wild-born ones in Oregon rivers.

Researchers created an enormous fish family tree using genetic samples from 12,700 steelhead trout (which are in the same family as salmon) returning from the sea to Oregon's Hood River to spawn. This fishy pedigree revealed the fish that spawned well in hatcheries had offspring that spawned poorly in the wild.

"They're adapting to captivity in a single generation," study scientist Mark Christie, a postdoctoral researcher at Oregon State University, told LiveScience. In other words, the fish rapidly became domesticated, Christie and his colleagues reported yesterday (Dec. 19) in the journal Proceedings of the National Academy of Sciences.

"It's similar to the process by which wolves were transformed into dogs," Christie said. "That's all that's occurring here, except it's occurring at a really rapid time scale." From LiveScience.com