Sensitivity of American Eels (Anguilla rostrata) and Atlantic Salmon (Salmo salar) to Weak Electric and Magnetic Fields

Abstract

Two long distance migrating fishes, the American eel (Anguilla rostrata) and the Atlantic salmon (Salmo salar), consistently showed conditioned cardiac responses to weak electric fields applied perpendicular but not parallel to their bodies. In fields with a power density of 0.11 × 10⁻³ pW/cm³, 63% of the eels tested were successfully conditioned, as were 56% of the salmon tested at 0.9 × 10⁻⁴ pW/cm³. At greater field intensities greater percentages of salmon and eels were successfully conditioned. However, at two lower intensities fewer salmon and no eels responded. These fields are of the magnitude that occur naturally in ocean currents. As geoelectric fields are perpendicular to the water motion that generates them, this sensitivity might allow a migrating fish to align itself upstream or downstream in an ocean current in the absence of fixed references. Results of magnetic conditioning experiments in eels were equivocal. Attempts to condition salmon to weak magnetic fields were unsuccessful.