Examining the Distribution and Spatial Interaction of Juvenile and Adult Sea Scallops with High-Resolution Still Imagery

The Atlantic sea scallop (Placopecten magellanicus) supports one of the world’s largest scallop fisheries, however, our understanding of factors that affect juvenile abundance and distribution is limited.  Recent surveys using high resolution imagery on Georges Bank and in the Mid-Atlantic have enabled the observation of juvenile scallops (<50 mm) in the wild, which was previously difficult.  Using these images, we compared levels of juvenile and adult crowding and examined spatial relationships over a range of scales.  Georges Bank juveniles were 2.6 to 7.4 times more crowded than all other scallops.  Juvenile and adult scallops were negatively associated at small scales (m²) and positively associated at larger scales (km²), with stronger negative correlation in the Mid-Atlantic.  These results suggest differing population dynamics between the Mid-Atlantic and Georges Bank.  Mid-Atlantic scallop recruitment seems to be highly dependent on favorable currents, causing infrequent large year classes.  Currents on Georges Bank may retain larvae more effectively, providing a steadier supply of young scallops.  Further, seafloor habitat is more heterogeneous, likely resulting in spatially variable levels of juvenile mortality.  This may lead to a more persistent bed structure on Georges Bank and a more cohort driven population structure in the Mid-Atlantic.