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Research Document - 1999/037

Seasonal Migration Patterns of Atlantic Cod (Gadus morhua) in Subdivision 3Ps Based on Tagging Experiments During 1997-1998.

By J. Brattey, G. Lawson and G. Rose

Abstract

Migration patterns based on recaptures of cod tagged in the inshore of Subdivision 3Ps and adjacent areas (inshore southern 3L) during 1997 and both inshore and offshore areas of 3Ps during 1998 are described. Cod tagged in Halibut Channel (N=1842) during April 1998 were recaptured offshore in small numbers throughout the year mostly within 50 nm of the tagging site; however, there were four recaptures in Placentia Bay during July-September indicating a portion of this offshore stock component moved inshore during summer. Cod tagged in the Hermitage Channel south of Burgeo Bank during early April were recaptured either inshore along the south coast of Newfoundland eastward to southern 3L, or north and westward to 3Pn4RS. Recaptures of spawning cod tagged in Fortune Bay during May 1998 came mostly from within Fortune Bay itself, with smaller numbers of recaptures westward along the south coast or eastward into western Placentia Bay; there were no recaptures from offshore 3Ps or inshore 3L, suggesting that these were predominantly an inshore south coast stock. Spawning and pre-spawning cod tagged at the head of Placentia Bay during 1997 and 1998 dispersed widely throughout the bay during the summer and in both years a portion migrated eastward across the stock boundary into southern 3L, approximately as far north as the eastern side of Trinity Bay. These cod appeared to migrate back into Placentia Bay during fall. The tag returns indicate that the 1998 summer and fall fishery in Placentia Bay exploited a complex mixture of stock components that included fish from Burgeo Bank, Halibut Channel, and Fortune Bay as well as 'local' fish. The numbers of Placentia Bay-tagged cod recaptured per unit weight of catch was compared between Placentia Bay and adjacent areas in southern 3L (St. Mary's Bay and southern Avalon, eastern Avalon, and Conception Bay). The comparison suggests that a substantial portion of the catch from southern 3L during 1998 was fish of 3Ps origin. In contrast, Placentia Bay-tagged cod were extremely rare further north in 3L (western Trinity Bay and Bonavista Bay) and in 3K in spite of considerable landings (>2,000mT).

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