Distribution and movements of Atlantic cod in Placentia Bay, Newfoundland

Abstract

This study investigates spatial and temporal variability in the distribution and movements of Atlantic cod (Gadus morhua L.) in Placentia Bay, Newfoundland, Canada, and consists of three components. First, a combination of acoustic and submersible surveys is used to reveal systematic variation in acoustic density estimates resulting from diel behavioural patterns of cod vertical movements and habitat associations. Second, acoustic measures of cod distribution demonstrate that cod spawn repeatedly at well-defined grounds in coastal Newfoundland, that the timing and intensity of spawning vary inter- and intra-annually, and that gender and age-related behaviours affect the composition of spawning shoals over time. Third, the within-year distribution and movement patterns of cod in Placentia Bay are studied using acoustic methods and mark-recapture experiments, documenting substantial migrations and a shift in depth-related distribution from the spring spawning to fall feeding period. This thesis reveals strong spatial and temporal trends in coastal cod distribution, demonstrating that acoustics can be effectively employed in the Newfoundland coastal environment. The observations provide evidence for the existence of a Placentia Bay cod stock.