EFFECTS OF SITE AND SEASON ON MOVEMENT FREQUENCIES AND DISPLACEMENT PATTERNS OF JUVENILE SEA SCALLOPS PLACOPECTEN-MAGELLANICUS UNDER NATURAL HYDRODYNAMIC CONDITIONS IN NOVA-SCOTIA, CANADA

In this study, we examine the effect of site and season (spring vs fal l) on the movement frequency and net displacement of juvenile sea scal lops Placopecten magellanicus, and the relationship between the net mo vement direction of scallops and the near-bed current direction at 2 s ites in Lunenburg Bay, Nova Scotia, Canada. At each site, a total of 1 50 and 100 individually marked juvenile sea scallops were released on the sea bed at 2 points (Stns 1 and 2) placed 50 m apart for the sprin g (March) and fall (September) studies. The movement frequency and net displacement of the scallops were monitored within a 10 m radius from the release point approximately once a week during the spring study, and once a day during the fall study. Current meters placed 60 cm off the sea bed recorded near-bed current velocity. There was a significan t interaction between site and season on the movement frequency of sca llops. Scallop activity was low during the spring study at both sites when similar to 30% of scallops were found at their release point on t he sea bed after 30 d. Scallops were much more mobile during the fall study when <5% of scallops were found at their release point after 2 d . However, the net daily displacement was <3 m for more than 60% of sc allops recorded. In similar to 50% of the surveys, the net movement di rection of scallops was significantly related to the direction of the main current vectors over daily to monthly periods, whereas in the oth er cases the net movement direction was independent of the direction o f the main current vectors. The results of this study indicate that lo cal hydrodynamics is not a good predictor of the swimming dispersion o f juvenile P. magellanicus in natural habitats.