GRANTS PASS, Ore. (AP) — Salmon have long been known to use their sense of smell to find their home river when it comes time to spawn, but how do they get close enough to smell the river? A new study suggests that, like birds on long migrations, salmon use the earth's magnetic field. The study this week in Current Biology looked at 56 years of fisheries data about which route sockeye salmon use returning to the Fraser River in British Columbia.

Scientists found that which way the salmon chose to go around Vancouver Island matched changes in the geomagnetic field. Lead author Nathan Putman, a researcher at Oregon State University, says they think salmon log in magnetic waypoints as they swim out to sea, then follow them back until they can smell the river.