Affiliation: | (1) Integrative Zoology, Institute of Biology Leiden, van der Klaauw Laboratorium, P.O. Box 9511, 2300 RA Leiden, The Netherlands;(2) Organization for Improvement of Inland Fisheries, Postbus 433, 3430 Nieuwegein, AK, The Netherlands |
Abstract: | Synopsis We studied the circadian and monthly activity, the distribution patterns, and orientation to the earths magnetic field, of yellow (non-migratory) female eels in a freshwater pond by means of microchips injected into their muscles. Detectors for microchips mounted in tubes were placed in the pond to detect if eels oriented themselves with respect to earths magnetic field. Based on the frequency of tube visits (search for shelter), the data indicated that the presence of eel in the tubes decreases gradually during the study period. We saw more activity during the night in the first months. There was a seasonal component in the orientation mechanism, with a significantly lower preference component in the summer compared to the fall. A preference for tubes oriented in a south-southwest direction (the direction of the Sargasso Sea) in fall suggests an orientation to the earths magnetic field. |