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 w aters of the Baie des Chaleurs, Quebec, Canada. Larvae aggregated at c ertain depths in both types of water column. When a pycnocline was pre sent, the mean depth of veligers was generally below it. Veligers' ver tical distribution was not related to that of water chlorophyll a exce pt at night in stratified conditions. In stratified waters, gut chloro phyll a content of larvae was associated with water chlorophyll a conc entration. In mixed waters, larval gut content was similar at all dept hs. Turbulence seemed to be associated with increased gut content. Die l vertical migration was observed for three of the four 24 h sampling periods and was apparently associated with an increase in feeding acti vity.