Iron, steel in hatcheries may distort magnetic “map sense” of steelhead, June 5

Exposure to iron pipes and steel rebar, such as the materials found in most hatcheries, affects the navigation ability of young steelhead trout by altering the important magnetic “map sense” they need for migration, according to new research from Oregon State University.  The exposure to iron and steel distorts the magnetic field around the fish, affecting their ability to navigate, said Nathan Putman, who led the study while working as a postdoctoral researcher in the Department of Fisheries and Wildlife, part of OSU’s College of Agricultural Sciences.  Just last year Putman and other researchers presented evidence of a correlation between the oceanic migration patterns of salmon and drift of the Earth’s magnetic field. Earlier this year they confirmed the ability of salmon to navigate using the magnetic field in experiments at the Oregon Hatchery Research Center. Scientists for decades have studied how salmon find their way across vast stretches of ocean.  “The better fish navigate, the higher their survival rate,” said Putman, who conducted the research at the Oregon Hatchery Research Center in the Alsea River basin last year. “When their magnetic field is altered, the fish get confused.”  Subtle differences in the magnetic environment within hatcheries could help explain why some hatchery fish do better than others when they are released into the wild, Putman said. Stabilizing the magnetic field by using alternative forms of hatchery construction may be one way to produce a better yield of fish, he said.