Atlantic Fisheries Research Document 1996/093

Overview of Atlantic cod (Gadus morhua) stock structure in NAFO subdivision 3Ps inferred from tagging studies

By J. Brattey

Abstract

Since the 1930s, an extensive series of tagging experiments, involving over 54,000 fish, have been conducted on cod stocks inhabiting various areas off the south coast of Newfoundland. Recaptures of over 13,000 of these cod, primarily by commercial fishermen, has shown that stock structure and migration patterns within this area are extremely complex. Interpretation of the recapture data indicates that attempts to estimate stock size within 3Ps are complicated by a seasonal influx of cod from adjacent managements units, notable the western Gulf stock (3Pn4R) from the west during winter, and possible southern Grand Banks (3LNO) from the south and east during fall. Migration of offshore components of the stock to inshore areas during spring and summer, as well as the possible existence of inshore components that remain outside the survey areas throughout the year, have also complicated the assessment of stock biomass. Tagging studies suggest that several components contribute to commercial catches in 3Ps; these include cod from the western Gulf, Burgeo Bank, southern St. Pierre Bank, southern Grand Banks, and the inshore Avalon-Burin stock complex. The origins of the cod that have contributed to the high catch rates observed during the Sentinel Survey in the last four months of 1995 are not known. Further tagging studies, particularly in Placentia Bay where coverage has been poor, could help elucidate the origins of these fish.

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