Horizontal and Vertical Swimming of Eels During the Spawning Migration at the Edge of the Continental Shelf

Abstract

Tracking experiments on migratory eels (Anguilla anguilla L.) on the shelf near the East Atlantic continental slope showed a NNW preferred compass direction (PCD) and confirmed earlier results in the North Sea. Eels tracked off-shelf (water depth more than 200 m) exhibited a westerly PCD with probably a slight tendency to the southwest (direction of the Sargasso Sea). Off shelf preferred hourly mean depths were 50 – 215 m at night. Short-term depth changes of 200 m occurred at a maximum. At dawn the eels showed a strong vertical downward migration. The preferred depths were probably greater than 400 m during daylight.