Abstract

Female silver eels (Anguilla anguilla L.) were tagged with data storage tags and released in the Baltic Sea at the same time at a single site on the east coast of Sweden. Data on temperature, light, and depth were obtained from six eels, continuous records for 71 d at sea. The swimming behaviour was similar for all fish, almost stereotyped: swimming activity was between dusk and dawn, starting at a light level corresponding to civic twilight and ending in the morning at generally the same light level. During daylight, the eels rested on the seabed at depths of 2-36 m. Swimming depth was typically close to the surface: up to 95% of swimming time was spent within 0.5 m of the surface. Short dives at irregular intervals (some 1-2 h(-1)) were made down to the thermocline depth, or occasionally, to the seabed. The duration of such dives were typically 5-10 min. Although only a few days at liberty, the eels had migrated a considerable distance between recapture and release sites, indicating a mean rate of travel of similar to 16 km d(-1). The recapture positions suggested unidirectional movements towards the southwestern Baltic Sea, i.e. close to the straits leading to the ocean, supporting a belief that the recorded movements were related to eel spawning migratory behaviour.

Keywords

diurnal behaviour; eel; migration; swimming depth

Published in

ICES Journal of Marine Science
2007, volume: 64, number: 7, pages: 1457-1462
Publisher: OXFORD UNIV PRESS

Authors' information