grew at a natural rate, but that their mortality rates may have 

 been increased by the tags. 



The "clapper" method of estimating mortality is dependent on 

 the time that it takes for the valves to separate after the 

 scallop has died. Based on laboratory experiments, Dickie (1955) 

 suggested that it took an average of 14 weeks for the valves of 

 the sea scallop to separate. Using shell deterioration in a 

 natural population, Merrill and Posgay (1964) estimated that it 

 took an average of 33 weeks for the valves to separate. The dead 

 tagged scallop treatments ( DEADE and DEADI ) in this study show 

 that after one year only half of the scallops had separated 

 valves (Figure 2). The tagged live scallops that died (LIVEDE 

 and LIVEDI ) show that only 17 percent of the scallop's valves had 

 separated after 8.5 + 3.5 months. Together, these scallop 

 treatments demonstrate how the valves of the sea scallop 

 deteriorate over time, from attached valves with a resilium to 

 unattached valves without a resilium (Figure 3). These 

 estimates, of how long the valves stay paired, vary widely and 

 indicate that this aspect of the clapper mortality estimate 

 should be investigated further. 



The biomass of the epizooic assemblage on the interior valve 

 of the sea scallop also has been related to the length of time 

 that a sea scallop has been dead (Merrill and Posgay 1964). The 

 biomass of the epizooic assemblages on the interior shell 

 surfaces (LIVEDI and DEADI) was significantly greater and more 

 variable than those on the exterior shell surfaces (LIVEDE and 

 DEADE); see Figure 3. Yet, there was no trend between the 

 biomass of the epizooic species on the interior valve surfaces 

 and the period that a tagged scallop had been dead. The absence 

 of this trend might be expected because epizooic species in the 

 Gulf of Maine have seasonal settlement cycles (DePalma 1969), and 

 they may not begin to develop until long after the scallop has 

 died. The fact that epizooic species richness was significantly 

 different between these assemblages suggests, however, that 

 epizooic composition may be useful for assessing the length of 

 time that a sea scallop has been dead. 



These data clearly demonstrate that the adult sea scallops 

 do not migrate because all of the recaptured individuals were 

 found within a 10 meter radius of their release site. The live 

 scallops were found in depressions in the sediment and the dead 

 scallops were found on the sediment surface (Figure 4). As 

 suggested from this study, tagged scallops do not distribute 

 themselves randomly over large areas and therefore, caution must 

 be used when extrapolating information from tagging studies to 

 the natural population. 



ACKNOWLEDGEMENTS 



In a practical sense, this study could not have been 

 conducted without the help and friendship of Rich Langton, Bill 

 Robinson, and Dan Schick. The generous assistance of the Maine 



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