Nearshore settlement and localized populations of age 0 Atlantic cod ( Gadus morhua ) in shallow coastal waters of Newfoundland

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Grant, Scott M, Brown, Joseph A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; atlantic cod; Gadus morhua; Newfoundland
• Online Access: http://dx.doi.org/10.1139/f97-310; http://www.nrcresearchpress.com/doi/pdf/10.1139/f97-310

Mark-recapture experiments and seasonal sampling were carried out to examine the nearshore movements, abundance, and behaviour patterns of age 0 Atlantic cod (Gadus morhua) in eelgrass (Zostera marina) and no-eelgrass habitat in Trinity Bay, Newfoundland, during 1994 and 1995. Cod remained localized, not moving further than a few hundred metres in eelgrass and no-eelgrass habitats for several weeks after settling from a pelagic habit, and may remain localized during their first winter. Observations from this study of bulk movements of marked and unmarked cod, high within-site variation in catch rates during the day, and significant day-night differences in the mean and variance of catch data, combined with results from related studies, provide indirect evidence that age 0 cod shoal during the day and disperse at night within the study area. Behaviour patterns exhibited by age 0 cod (restricted nearshore movements, diurnal shoaling, and preference for structurally complex habitat) are mechanisms for predator avoidance, suggesting that predation risk is high in coastal Newfoundland. A significant increase in abundance of age 0 cod in less suitable habitat (no-eelgrass cover) when settlement strength was high is consistent with the hypothesis of density-dependent habitat selection.