Orientation and Navigation of the European Eel Using the Earth's Magnetic Field and Its Possible Implications for Management

Little is known about the orientation cues used by eels to guide their short- and long-distance migrations. The Earth’s magnetic field can provide directional and positional information to an individual that possesses magnetosensitivity. Magnetosensitivity has earlier been reported in salmon and tuna, and was recently demonstrated in yellow and silver eels. Eels oriented in a manner that was related to ambient temperature and to a transitory displacement immediately before the test. Their ability to position themselves relative to the Earth’s magnetic field can be used for orientation along a river axis (to learn the direction of the main flow) and in the open sea (to maintain a compass heading). Eels may derive positional (map) information from the Earth’s magnetic field and use it to navigate to distant spawning grounds. This would involve imprinting the location of the spawning grounds by larvae. We discuss this possibility with regards to secular variation and the physical properties of the geomagnetic field over the course of their hypothetical migratory route. Understanding the eel’s orientation and navigation mechanisms is crucial to evaluating the potential effectiveness of current management measures which typically involve translocating juvenile eels 100s to 1000s of km.