Depth-dependent vertebral number of Atlantic cod ( Gadus morhua ) on the Magdalen Shallows and Scotian Shelf: stock mixing or microgeographic trends within populations?

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Swain, D P, Frank, K T
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2000
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Magdalen; atlantic cod; Gadus morhua
• Online Access: http://dx.doi.org/10.1139/f00-218; http://www.nrcresearchpress.com/doi/pdf/10.1139/f00-218

We examined spatial variation in the vertebral number of Atlantic cod (Gadus morhua) during the summer feeding season in the southern Gulf of St. Lawrence and on the Scotian Shelf. Mean vertebral number increased significantly with depth in the southern Gulf and on the northeastern Scotian Shelf but not on the southwestern Scotian Shelf. In the southern Gulf, where sampling was most extensive, mean vertebral number increased steadily as depth increased from 25 m to over 175 m. Mean vertebral number was also strongly related to relative length within age-classes, with the larger fish at age having more vertebrae. However, the association between vertebral number and depth could not be attributed to confounding between depth and size at age. These results indicate either unexpected mixing between neighbouring cod populations or unexpected structure at fine spatial scales within cod populations.