BIOLOGY AND NATURAL HISTORY 173 



many areas shortly afterwards. Since that period wherever patches of eel- 

 grass have appeared scallops have soon followed. Many studies have shown 

 a possible positive correlation between the abundance of eelgrass and bay 

 scallops, but as Marshall (1947) points out, the relationship is complex and 

 indirect. Forms other than scallops disappeared from some areas following 

 the eelgrass. Stauffer (1937) describes the absence, five years after eelgrass 

 disappeared from an area, of nine out of thirteen species that had been 

 found in a former typical eelgrass habitat. Marshall (1947) reports scallops 

 flourishing in the absence of eelgrass in Long Island Sound. Belding (1910) 

 and Outsell (1931) both suggest that eelgrass was important in offering a 

 surface for attachment of young scallops and afforded some means of pro- 

 tection to the adult. The presence of any suitable grass, algse, or other 

 surface for attachment would be expected to serve the same purpose. Scallops 

 do occur in commercial quantities in New England, presumably because 

 the rocky, weed-covered bottom offers a surface for attachment and some 

 protection. A few young scallops were recently found attached to old shells 

 and bryozoa in Core Sound, North Carolina. Market-sized scallops occur 

 sporadically in the vicinity of Hatteras and the western end of Bogue Sound 

 usually correlated with the appearance of some eelgrass. 



GROWTH. The growth of the scallop is rapid in comparison with the oyster 

 and the clam. A marketable size of three inches in diameter is attained in a 

 year or even less in the waters of North Carolina. According to Outsell 

 commercial crops are of an age group between 12 and 20 months. Belding 

 reports that few scallops live to be 2 years old but found a few living to 

 an age of 30 months. In controlled experiments Belding showed that un- 

 molested scallops in their second year begin to show signs of physical de- 

 cline by slower growth, thickening of shell, and degeneration of the adductor 

 muscle, and by becoming more susceptible to adverse conditions. Twenty 

 per cent of the scallops reach the two-year mark and probably less than 10 

 per cent pass it. This factor has been the justification for protecting scallops 

 less than one year of age, for they spawn to provide future seed. Spawning 

 may occur in the second year, but the majority of the scallops die before 

 their second spawning. 



Orowth lines or annual rings corresponding to the one-and two-year 

 periods are characteristically found on the shell. Belding attributes the for- 

 mation of the annual ring to cessation of shell growth during the winter 

 months. Outsell says that the ring is formed in the North Carolina waters 

 usually in the fall and thus is not correlated with cold weather. Risser 

 (1901) showed that the growth line corresponds well with the spawning 

 period. The most plausible explanation of the growth line appears to be 

 the correlation with spawning. 



