are released directly into the water column where fertilization takes place. 

 Eggs and larvae are planktonic. Fertilized eggs hatch in approximately 30 to 

 40 hours, undergo the usual molluscan larval stages of development (Culliney 

 1974), and the larvae remain planktonic for a month. As they metamorphose 

 into spat they attach to such objects as broken and whole shells (including 

 live scallops), bryozoa, red algae, pebbles, metal, and wooden objects 

 (Mackenzie 1979). After a year the spat descend to the bottom to live as 

 unattached benthic organisms. During their planktonic stage they are at the 

 mercy of the prevailing currents. It is thought that, with the exception of 

 Georges Bank, the "down current" areas are probably populated with larvae from 

 "up current" populations due to a semi -persistent gyre which may retain the 

 larvae until they become benthic (Posgay 1982). 



The sea scallop is a filter feeder, consuming phytoplankton and some 

 organic detritus (Posgay 1982). 



At present, the 1972 year-class still dominates the population. Survey 

 abundance indices show that, with the exception of eastern Georges Bank and 

 the Virginia-North Carolina area, recruitment from the 1973, 1974, and 1975 

 year-classes continues to be poor. Landings remain high, but this is due to 

 increased fishing effort rather than an increased stock size (Serchuk et al . 

 1979). 



Bottom Trawl Survey Results 



The cumulative spring and autumn di strubutions over the time series are 

 shown in Figures 20.1 and 20.2. Since scallops are mobile, but do not 

 migrate, the seasonal distributions are similar. 



The graphs of mean weight and number per tow (Figures 20.3-20.6) indicate 

 some seasonal sampling inconsistencies. Trawls with roller sweeps decrease 



43: 



