BBC: The migration of adult sockeye salmon from the northern Pacific Ocean back to the freshwater rivers where they were born is one of the most incredible of any species. How the fish find their way has been the subject of much debate, and one of the primary theories was that they used Earth’s magnetic fields. Nathan Putman of Oregon State University and his team examined 56 years of data on salmon migrations back to the Fraser River in British Columbia, Canada. When the team compared the local magnetic field variations along the river to the magnetic field around Vancouver Island, they found that the salmon chose their route around the island by selecting the local magnetic field intensity that matched that of the intensity near where they were born. How the fish remember or detect information about the magnetic field is not yet known, but it may be tied to olfactory abilities.