Winter distribution and movements of northern Atlantic cod (Gadus morhua) along the Newfoundland—Labrador continental shelf edge derived from observations on commercial trawlers

Abstract

Catch‐effort data recorded by observers aboard commercial trawlers fishing the Newfoundland‐Labrador continental shelf during the winters of 1980–1991 were used to define the distribution and movements of pre‐spawning and spanning Atlantic cod, Gadus morhua. Although cod were widely distributed over the outer continental shelf in the months of January to April, commercial concentrations were consistently located in three areas along the shelf edge. These three areas, constituting only 16% of the 190000 km2 fishing ground for northern cod, were centred north‐east of Belle Isle Bank, north‐east of Funk Island Bank, and between Funk Island Bank and the northern Grand Bank Tow positions with catch rates 5000 kg h‐1 were plotted on a weekly basis to define movements of cod schools during the winters of 1986–1988. It was assumed that change in the collective position of trawlers taking large quantities of cod reflected shoal movements. Analyses indicate that cod moved southeast along the shelf edge in January and February of each year, crossing from NAFO Division 2J into 3K Each March, cod in Division 3K apparently moved northwest against prevailing ocean currents into the Hamilton Bank region of 2J. These movements do not appear to be a direct response to ocean temperature or pack ice conditions, although cod moving along the shelf break were generally in bottom waters of 24°C. We suggest these patterns reflect the migratory behaviour of pre‐spawning and spawning cod.