The use of transplantation-tagging-experiments in studies of migratory diversity of cod off Norway

Abstract

Cod along the Norwegian coast show great variability in migration. Coastal Cod may be stationary for the whole life while mature Northeast Arctic Cod migrate long distances to reach the feeding areas in the Barents Sea and the spawning areas along the Norwegian coast. In this paper migratory differences and possible mechanisms behind them are studied by transplanting the two types of cod to new locations and study their behaviour after release. Individual behaviour is examined by logging information from acoustic transmitters attached to the fish giving continuous data on position and depth. The data, although limited, show clear differences in migratory restlessness in Coastal Cod and Northeast Arctic Cod; the first showing a territorial behaviour compared to a more active and determined migration for the second, particularly in winter time. The use of low frequency noise from oceanic waves is suggested to be a possible navigation stimulus for Northeast Arctic Cod to find back to oceanic waters.