Sea scallop larvae Placopecten magellanicus on Georges Bank: vertical distribution in relation to water column stratification and food

Abstract

[Vertical distribution of sea scallop larvae was studied from pump samples in mixed, stratified, and frontal areas of Georges Bank. The extent of larval aggregation was positively related to the degree of water column stratification. In mixed areas larvae were distributed evenly over the 40 to 50 m water column, while in stratified waters larvae showed subsurface peaks in concentration above the pycnocline. Where the pycnocline was well developed, differences in the larval centre of mass (ZCM) were associated with differences in the position of the pycnocline. Food for sea scallop larvae was measured as the concentration of chlorophyll a < 15 μm and particles 2.5 to 16 μm. In stratified areas food was usually greatest within the upper 10 m. Sea scallop larvae were most concentrated below 10 m and did not aggregate in relation to food concentration. The capacity of sea scallop larvae for depth regulation on Georges Bank appears limited, since there were no diel differences in the ZCM, and sizedependent differences in vertical distribution were weak and inconsistent.]