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Metal at hatcheries confuses migratory fish

Metal building materials used in most fish hatcheries have a negative effect on the species the facilities are designed to help.

Iron rebar and steel pipes interfere with the magnetic field around young steelhead trout, confusing their map sense critical to migration, according to a study by Oregon State University researchers published this week in the journal Biology Letters.

“The better fish navigate, the higher their survival rate,” says Nathan Putman, who conducted the research. “When their magnetic field is altered, the fish get confused.”

Last year, Putman found evidence that salmon migrational patterns correlate with the Earth’s magnetic field. He repeated the experiment with steelhead trout and received similar results.

Researchers are unsure whether the distortion of a fish’s magnetic map sense is permanent or temporary from the materials in the hatchery. However, Putman recommends changing materials in proximity to developing fish.

“You can fix these kinds of things,” Putman says. “Retrofitting hatcheries with non-magnetic materials might be worth doing if it leads to making better fish.”

Oregon Sea Grant and the Oregon Department of Fish and Wildlife funded the research, with support from Oregon State University. OSU’s David Noakes, senior scientist at the Oregon Hatchery Research Center, and Amanda Meinke of the Oregon Hatchery Research Center are co-authors of the study.

Kate Stringer can be reached at 503-357-3181 or This email address is being protected from spambots. You need JavaScript enabled to view it.

Twitter: @KateStringer2

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