Now, researchers at the University of Miami and the Norwegian Institute of Marine Research have shown that the eels use Earth's magnetic field to determine which direction to swim. In a Norwegian fjord, they placed locally caught glass eels in a mesh container that was suspended from a surface float. A camera recorded the behaviour of the eels and the team found that they tended to swim in a southerly direction at ebb tides. The same glass eels were then placed in a specially designed tank in which they are shielded from external stimuli such as daylight. Magnetic fields were applied to the tank, which effectively rotated the magnetic north–south axis by 90°. During periods of ebb tides, the team found that the eels oriented themselves in a southerly direction as defined by the applied magnetic field. This led them to conclude that the glass eels navigate using Earth's magnetic field in a manner that is linked to the local cycle of tides. This, they believe, could help the eels to use the tides to reach freshwater in rivers. "It is incredible that these small transparent glass eels can detect the Earth's magnetic field," says Miami's Alessandro Cresci. "The use of a magnetic compass could be a key component underlying the amazing migration of these animals," he adds. "It is also the first observation of glass eels keeping a compass as they swim in shelf waters, and that alone is an exciting discovery."
Wednesday, June 14, 2017
Hey, Norway gets a mention, too: