scallop had been dead was estimated by dividing the total shell 

 growth by the shell growth rate for that specific sized scallop 

 as shown in Figure 1. The tagged live scallops (LIVEDE and 

 LIVEDI ) had been dead for 8.5 + 3.5 months, whereas the tagged 

 dead scallops (DEADE and DEADI ) all had been dead since the 

 beginning of the experiment. Seven percent of the initially live 

 tagged scallops (LIVEDE and LIVEDI) had fractured hinges, 

 suggesting predation. Figure 2 shows how the hinge and resilium 

 deteriorate after the sea scallop dies. 



Sea Scallop Epizooic Assemblages 



Biomass and composition. 



The relationship between epizooic settlement and the amount 

 of time that a mollusc has been dead have been investigated in 

 oysters ( Gunter et al. 1957), clams (Driscoll and Swanson 1973), 

 and scallops (Merrill et al. 1966). There were 55 species from 8 

 phyla represented in the offshore tagged scallop epizooic 

 assemblages. These assemblages included juvenile sea scallops 

 (less than 1 cm in height) and small Cancer borealis, both of 

 which were found inside of the dead tagged scallops. Figure 3 

 shows that there were consistent differences between the epizooic 

 biomass on the interior and exterior shell surfaces of the 

 initially live tagged scallops (LIVEDE and LIVEDI) and of the 

 dead tagged scallops (DEADE and DEADI). The differences between 

 these treatments were compared with paired t-tests and were 

 significant at P = 0.05. Jackknifed comparisons of species 

 richness (Heltshe and Forrester 1983) also indicated that these 

 assemblages were significantly different. 



DISCUSSION 



Tagging studies have been an important means of assessing 

 the growth, movement and mortality of the sea scallop. However, 

 interpretations from these studies have been based on low returns 

 (less than 15 percent), experimental errors introduced by scallop 

 dredges, and by inaccurate methods of reporting recapture 

 information ( Posgay 1963, Merrill et al . 1966). The use of 

 manned-submersibles provided a method for recapturing over 58 

 percent of the tagged live scallops (LIVETAG, LIVEDE and LIVEDI) 

 and an in situ view of the tagged scallop population. 



Because a large percentage of the tagged scallops were 

 recaptured, it is possible to speculate how the tags affected sea 

 scallop mortality and growth. The annual mortality rate, 

 estimated for the recaptured tagged scallops that died between 

 July 1986 and July 1987, was over 65 percent. Mortality 

 estimates based on the proportion of "clappers" (dead scallops 

 with paired valves; Dickie 1955) in the population are around 

 0.10 (Merrill and Posgay 1964). However, the tagged scallop 

 growth rates calculated in this study were not significantly 

 different from those of other studies (Merrill et al . 1966). 

 These data suggest that while the tagged scallops were alive they 



235 



