Research Document - 2005/055

Migratory routes and stock structure of cod from the Northern Gulf of St. Lawrence (3Pn, 4RS)

By Yvelin, J.-F., A. Fréchet,
J.-C. Brêthes

Abstract

Atlantic cod (Gadus morhua) is a migratory fish, and the general migration patterns of the northern Gulf of Saint-Lawrence stock (3Pn, 4RS) are well known. In the 80’s, more then 45,000 cod were tagged in the northern Gulf by the Department of Fisheries and Oceans and the Department of Agriculture, Fisheries and Food of Québec. Since 1995, close to 60,000 cod have also been tagged in the northern Gulf by the Sentinel Program. For our study, only the fish recaptured less than one year after their tagging have been selected. The analysis of these short term data has confirmed the migratory corridors of the 3Pn, 4RS stock; it also enabled to observe their evolution in the last twenty years. Cod show a homing behaviour, as the recapturing of a lot of fish about one year later, less than nine kilometres from their tagging area proved. Moreover, the 3Pn, 4RS stock seems to be divided in at least four subpopulations. All of them spend winter at the same place, but two of them have got a different summer distribution, one subpopulation seems to be resident all year long south of Newfoundland, and another one, living off Anticosti Island during the summer, looks as if it has already disappeared. Finally, the possibilities of stocks mixings, already mentioned in many studies, seem to be confirmed. It looks fundamental to carry out many other works (studies) in order to quantify these mixings and their impact on the north-west Atlantic cod stocks management.

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