DISPERSAL AND GROWTH OF PELAGIC JUVENILE ARCTO-NORWEGIAN COD (GADUS-MORHUA), INFERRED FROM OTOLITH MICROSTRUCTURE AND WATER TEMPERATURE

Dispersal of pelagic juvenile cod (Gadus morhua) off northern Norway from the main Lofoten spawning grounds to the western Barents Sea is regulated by the north-easterly circulation of the Norwegian coastal current (NCC). In July 1988 the smallest cod occurred within the spawning area (25.2 mm standard length, SL). but offshore small cod consistently occurred furthest from, rather than nearest to, the spawning area. The average SLofcod was 37 mm just offshore from the spawning area near Lofoten, 35 nun on the main post-larval nursery area on Tromsoflaket, and 33 mm in the western Barents Sea. Otolith microstructure analysis revealed no comparable difference in age. the mean age of cod ranging between 61 -65 days post-hatch throughout the offshore distribution. Cod offshore of Lofoten were distinguished from other cod by significantly greater length at age. higher condition factor (dry weight adjusted for length), and a different growth history. Change in SL back-calculated from the summed width of seven daily increments of the otolith, for each of 6 weeks before capture, revealed significantly greater growth for cod offshore from Lofoten which was correlated with water temperature. The slightly slower growth of cod in the western Barents Sea is consistent with transport in the colder NCC from the Lofoten spawning ground, while faster growth of cod offshore of Lofoten is consistent with transport in warmer Atlantic Ocean water, originating from the southern Mare coast spawning areas. © 1993 Conseil International pour l’Exploration de la Mer.