Abstract
Observations in 1991 along randomly placed transects within two aggregations (beds) of the giant scallop, Placopecten magellanicus, in Port Daniel Bay, Baie des Chaleurs, Gulf of St. Lawrence, showed that scallops were oriented randomly. During 1992, tag–release experiments were conducted on scallops at four sites, two on gravel (one in each of the above beds), one on sand, and one on bedrock, to examine the effects of current on scallop orientation over time. Current directions and velocities were measured at each site. Circular statistics applied to orientation distributions showed that scallops at the sites with gravel or sand substrata were randomly oriented and also changed orientation between successive observations at random. In contrast, at the bedrock site, scallops were significantly oriented and shifts of 120°–150° between successive observations were less frequent than would occur at random. The differences at the bedrock site possibly occurred because the scallops could not recess into the substratum and were thus more directly exposed to bottom currents. Although giant scallops have the capacity to orient themselves to current, they likely do not do so on gravel or sand substrata if current velocities are below 18.3 cm∙s
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