PLANKTONIC SEA SCALLOP LARVAE (PLACOPECTEN-MAGELLANICUS) IN THE GEORGES BANK REGION - BROADSCALE DISTRIBUTION IN RELATION TO PHYSICAL OCEANOGRAPHY

During autumn surveys for sea scallop larvae (Placopecten magellanicus) from 1985 to 1987, the mean abundance of sea scallop larvae on the northeast part of Georges Bank (1201-20080.m-2) was much greater than on the southern Scotian Shelf (5-240.m-2). Few larvae were collected between these two areas, and exchange between Georges Bank and the Scotian Shelf appears very limited. Transects across the northern flank in 1988 revealed peaks in larval abundance when on-bank temperature stratification was high. Relative larval abundance on the transects was positively related to the speed of the along-front current, suggesting physical convergence of larvae. The on-bank retention of scallop larvae on Georges Bank appears to be due to physical processes alone, since scallop larvae undertake only limited diel vertical migration. Larval exchange among adult scallop aggregations on Georges Bank (the northeast peak, the southeast part, and the South Channel) is probable, but evidence from this study is limited. The autumn production of late-stage larvae on the northern flank and northeast peak of Georges Bank is estimated to range from 120 to 1500.m-2, which is 10-1 00 times greater than the density of scallops aged 1-2 yr.