Research Document - 1999/103

Stock Structure and Seasonal Migration Patterns of Atlantic Cod (Gadus morhua) Based on Inshore Tagging Experiments in Divs. 3KL During 1995-97.

By J. Brattey

Abstract

During 1995-1997, a total of 11,975 cod were tagged with t-bar anchor tags and released at various inshore locations in Divs. 3KL from statistical area 3Kd (Northern Peninsula) southward to 3Lq (St. Mary's Bay). Most tagging was conducted during July-September and the spatial extent of coverage varied among years. Tagged cod were reported as recaptured mainly during the sentinel survey (1996-1998), summer recreational fisheries (1996 and 1998), a fall inshore "index " fishery (1998 only), and during by-catch from fisheries directed at other species such as herring, lumpfish, and winter flounder. A total of 504 tagged cod have been reported as recaptured up to the end of 1998. The results indicate that the inshore of 3KL is inhabited by at least two groups of cod: (1) a resident inshore group that inhabits northern 3L and 3K from approximately western Trinity Bay northward, and (2) a migrant group from 3Ps. The migrant group may constitute the bulk of inshore cod inhabiting southern 3L (eastern Trinity Bay southward) during summer and early fall, but only a small proportion of cod in northern 3L and 3K. There appears to be considerable seasonal movement along the inshore with a counter-clockwise, northward movement of some inshore cod around the eastern portion of insular Newfoundland during summer. A southward return migration presumably occurs in late fall and early winter, but this could not be confirmed from tag returns due to lack of fishing activity at that time of year. Inshore-offshore movement of tagged cod may also have occurred, but such movement could not be detected due to the lack of offshore fishing activity associated with the moratorium on northern (2J-3KL) cod.

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