Transplantation-tagging-experiments in preliminary studies of migration of cod off Norway

Abstract

Cod along the Norwegian coast show great variability in migration habit. Coastal cod may be stationary for their entire life while mature north-east Arctic cod migrate long distances to reach their feeding areas in the Barents Sea and spawning grounds along the Norwegian coast. In this paper, migratory differences and possible mechanisms behind them are studied by transplanting the two types of cod to a new location and studying their behaviour after release. Individual behaviour is examined by logging information from acoustic transmitters attached to the fish which give continuous information on position and depth.

The data, although limited, show clear differences in migratory activity in coastal cod and north-east Arctic cod; the first show a territorial behaviour compared with a more active and determined migration for the second. It is apparent that the transplantation of north-east Arctic cod induces migratory activity. Low-frequency noise from oceanic waves is suggested as a possible navigational clue for north-east Arctic cod to find their way back to oceanic waters.