SOURCES OF ZOOPLANKTON ON THE NOVA-SCOTIA SHELF AND THEIR AGGREGATIONS WITHIN DEEP-SHELF BASINS

A large-scale survey/study of zooplankton on the Scotian Shelf south of Nova Scotia was performed during 1984-1985. Rapid sampling was accomplished using a Batfish vehicle mounted with an optical plankton counter, a multiple opening/closing net system (BIONESS), and multifrequency acoustics. From the Batfish survey reported here, we present evidence indicating that the dominant supply of zooplankton to the Scotian Shelf is provided by the Nova Scotia Current, a strong localized flow adjacent to the coast. During late winter and spring, the Nova Scotia Current supplies our shelf water with most Calanus species which originate from the Gulf of St Lawrence to the north. Further sampling indicated that the deep Scotian Shelf basins harbor large populations of zooplankton during autumn and winter which consist mainly of stages IV and V of C. finmarchicus, C. hyperboreus, and C. glacialis. This winter storage mechanism is also a dominant source of young copepedite stages in surface waters during the spring. Weak circulation within the shelf basins ensures that copepod populations are not displaced throughout the year.