Orientation of the American Eel, Anguilla rostrata

Abstract

The use of geomagnetism as a navigational aid by American and European eels during their seaward migration has recently been and currently is an area of research. This investigation reviewed previous studies concerning the use of geomagnetism as well as light and olfaction as guidance mechanisms during various life stages of American and European eels. In this study yellow-phase and silver-phase American eels were investigated for their orientational (directional) preferences in a chambered tank. The eels were observed while the tank was rotating and while the tank was stationary. In general, the eels were found to prefer easterly directions--particularly northeast. The variability with which the eels sought their preferred directions decreased or increased depending upon whether they were examined in the tank while it was rotating or while it was stationary. It is believed that because no other orientational cues were available to the eels during testing, the orientation which was observed to occur was dependent upon geomagnetism. This supports some current theories that eels make use of directional cues derived directly from the earth*s magnetic field or from oceanic electric fields which are associated with the geomagnetic field in making their long migration across the open sea to their breeding places in the Sargasso Sea.