Migrations and Intermingling of Atlantic Cod (Gadus morhua) Stocks of the Newfoundland Area

Abstract

Commercial recaptures of 26% (22.5% in years after the tagging year) of 18,822 Atlantic cod (Gadus morhua) 50 cm or more in length that were tagged mainly in the feeding season at 13 localities in the Newfoundland area in 1954–55 elucidated migrations and intermingling of cod of various stocks or stock complexes. Cod of the northern Gulf of St. Lawrence stock migrated southward from the Strait of Belle Isle to winter on the northern side of Cabot Strait and vicinity, mingling there with the Burgeo Bank stock. Cod of the Newfoundland–Labrador complex tagged at three sites mingled along the east coast of Newfoundland and off southern Labrador and with cod of the northern Gulf stock near the Strait of Belle Isle, of the Avalon–Burin stock complex off the Avalon peninsula, and of a Grand Bank stock on the northern part of the bank. Though cod tagged off the Avalon peninsula and on St. Pierre Bank were recaptured mainly near the tagging sites, some moved as far north as Labrador, to the southern Grand Bank, and to Cabot Strait. Fish tagged on the northwestern Grand Bank were recaptured mainly at the tagging site but also elsewhere on the bank and off the east coast of Newfoundland. Those tagged on the Southeast Shoal of the Grand Bank were recaptured mainly on the southeastern part of the bank though some moved as far as southeastern Newfoundland. Those tagged on Burgeo Bank mingled with the Avalon–Burin stock complex, including the St. Pierre Bank component, but mainly with the Northern Gulf stock in winter–spring near Cabot Strait.Cod 90–129 cm long at tagging were recaptured at shorter distances from the tagging sites than 50–89-cm cod. Tagging–recapture distances also increased with increasing age for cod of the smaller length ranges on tagging. In their vertical movements, most tagged cod moved to shallow water in late spring or early summer and retreated gradually to deeper water from late summer to early spring. Some remained in deep water throughout the year.Recapture rates at different size ranges varied with area but were not greatly different at length ranges from 50–59 to 80–94 cm, which included 95% of the tagged cod.