Research Document - 2005/071

Exploitation of Atlantic cod (Gadus morhua) in NAFO Subdiv. 3Ps: further updates based on 1997-2004 mark-recapture data

By Brattey, J., B.P. 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 65,400 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 12,603 (19.2%) have been reported as recaptured to 20 September 2005. No new tagging was conducted in the inshore of 3Ps during 2004. Estimates of exploitation for cod tagged in each region in each year were computed using methods reported in our previous document; values for 2005 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 (3Psc) mean annual estimates of exploitation have declined from 34% in 1999 to 20% in 2004. For cod tagged in Fortune Bay (3Psb) mean annual estimates have been similar (10-11%) during 2000-2003, but declined slightly to 8.1% in 2004, with tag returns indicating considerable movement of cod between Fortune Bay and Placentia Bay. For cod tagged in 3Psd (Burgeo Bank) the estimate for 2004 was 2.1%, comparable to the 2% estimated for 2003. Mean annual estimates of exploitation for cod tagged in offshore areas (3Psh) remain consistently low (2.2% for 2004 and ranging from 1.5-3.5% during 1998-2003) in spite of offshore landings of >6,000 t. Offshore tagging coverage was again expanded during 2004 with the assistance of industry, and approximately 1,750 tagged cod were released in southern 3Psh during December. To date, 47 of the cod tagged offshore in December have been reported as recaptured. Results were almost identical to those for cod tagged offshore in December in 2003, with recaptures taken either in the local offshore area (3Psh) or within Placentia Bay (3Psc).

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