Farm fish can jump the fence and cause trouble for their wild relatives.
Arctic Science Journeys reporter Robert Hannon has more. Salmon farming is a rapidly growing business in the chilly coastal waters of the northern U.S., Canada and Europe. But salmon sometimes escape from their pens, and that has scientists worried about the future of wild salmon stocks. Mary Colligan is a biologist for the National Marine Fisheries Service. She's studying what happens when Atlantic salmon escape and breed with their wild counterparts in Maine.