Research Document - 2004/084

Exploitation of Atlantic cod (Gadus morhua) in NAFO Subdiv. 3Ps: further updates based on tag returns during 1997-2004

By John Brattey and Brian Healey

Abstract

This document updates the results of a multi-year tagging study of Atlantic cod (Gadus morhua) in NAFO Subdiv. 3Ps, initiated during spring 1997. Since inception, a total of over 63,700 cod have been tagged with single, double, or high-reward t-bar anchor tags and released at various inshore and offshore sites off southern Newfoundland (3Ps) and 18.5% have been reported as recaptured to 10 September 2004. Estimates of exploitation for cod tagged in each region in each year were computed using methods similar to those reported in previously, but with minor modifications; values for 2004 are preliminary as the fishery was still in progress. Estimates of short-term tagging mortality, tag loss, and reporting rate were obtained and are incorporated into the estimation. Among cod tagged in Placentia Bay mean annual estimates of exploitation have declined from 34% in 1999 to 22% in 2003; however, some individual estimates remain quite high with four of seven estimates exceeding 25% in 2003. Mean annual estimates for cod tagged in Fortune Bay have been similar (10-11%) over the past four years, although cod tagged in the inner reaches of Fortune Bay at Poole's Cove have been more heavily exploited (20-31%) than those tagged in the outer reaches off Pass Island (4 to 6%). Tag returns indicate considerable movement of cod between Fortune Bay and Placentia Bay. Exploitation of cod tagged in 3Psd (Burgeo Bank) appears to have declined to only 2% in 2003 (compared to 4%-9% during 1998-2002); this decline may be due to closure of the directed cod fishery in the neighbouring northern Gulf management area (3Pn4RS) during 2003 as well as seasonal closures and restrictions to the directed cod fishery in western 3Ps (3Psa, 3Psd, and more recently 3Pse/g). Reported commercial landings from 3Psa/d during November-April 2002/2003 were only 260 t and for 2003/2004 totaled 507.7 t. These data suggest that potential removals of 3Pn4RS cod from winter fisheries in western 3Ps in the past two management years are relatively small and likely to have little influence on the dynamics of that stock. Mean annual estimates of exploitation during 2003 for cod tagged in offshore areas of 3Ps (3Psh) remain consistently low (1-2%) in spite of offshore landings of >6,000 t. Offshore tagging coverage was expanded during 2003 with the assistance of industry, and approximately 1,000 tagged cod were released in southern 3Psg and 3Psh during December. To date, only 10 of the cod tagged offshore in December have been reported as recaptured, one from Placentia Bay, six from offshore 3Ps and three from unknown locations in 3Ps.

Complete Document

Part 1 - Text and Tables (PDF, 154 KB)

Part 2 - Figures 1-5 (PDF, 3,933 KB)

Part 3 - Figures 5-7 (PDF, 5,905 KB)