The genetic impact of hatcheries on salmon is so profound it can create fish that struggle to thrive and reproduce in a wild environment, U.S. researchers say. Genetic traits are selected within a single generation that allow fish to survive and prosper in the hatchery environment but put them at a disadvantage in a natural setting, researchers at Oregon State University said Monday. \"We\'ve known for some time that hatchery-born fish are less successful at survival and reproduction in the wild,\" Michael Blouin, a professor of zoology, said in an OSU release. \"However, until now, it wasn\'t clear why. What this study shows is that intense evolutionary pressures in the hatchery rapidly select for fish that excel there, at the expense of their reproductive success in the wild.\" While hatcheries are efficient at producing fish for harvest, the study findings raise concerns about the genetic impacts hatchery fish may have when they interbreed with wild salmon, scientists said. The speed of the genetic changes came as a surprise to researchers. \"We expected to see some of these changes after multiple generations,\" Mark Christie, an OSU postdoctoral research associate and lead author on the study, said. \"To see these changes happen in a single generation was amazing. Evolutionary change doesn\'t always take thousands of years.\"