Relationship between feeding and vertical distribution of bivalve larvae in stratified and mixed waters

We documented the vertical distribution, species composition, size and feeding of bivalve veligers in vertically stratified and well-mixed waters of the Baie des Chaleurs, Quebec, Canada. Larvae aggregated at certain depths in both types of water column. When a pycnocline was present, the mean depth of veligers was generally below it. Veligers' vertical distribution was not related to that of water chlorophyll a except at night in stratified conditions. In stratified waters, gut chlorophyll a content of larvae was associated with water chlorophyll a concentration. In mixed waters, larval gut content was similar at all depths. Turbulence seemed to be associated with increased gut content. Die1 vertical migration was observed for three of the four 24 h sampling periods and was apparently associated with an increase in feeding activity.