Hampshire border) and Damariscotta Rivers. At one time the Sheepscot estuary 



supported scallops in abundance but they have largely disappeared. There is 



no proven explanation for the disappearance. Commercially valuable scallop 

 beds are illustrated in atlas map 4. 



Life History 



Scallops in Maine waters are reported by Baird (1967) to reach sexual maturity 

 in the third or fourth year of life or at the size of 2.2 to 2.9 inches (56 to 

 74 mm). Spawning occurs from July to October, with peaks in late August in 

 eastern Maine (region 6; Bourne 1964) and in September in Penobscot Bay 

 (region 4; Baird 1953). Spawning is believed to be triggered by a slight 

 change in temperature; however, some investigators believe a rise in 

 temperature is necessary (Culliney 1974) whereas others claim a drop in 

 temperature initiates spawning (Altobello et al. 1976). According to Culliney 

 (1974) optimal temperatures for successful spawning of natural populations is 

 about 46 to 52°F (8 to 11°C). 



No information is available on the number of eggs released per individual; 

 however, it can be assumed that numbers would be several million, as is 

 typical of large molluscs (TRIGOM 1974). Sexes are separate, and gametes are 

 released into the surrounding water where fertilization occurs. The larvae 

 are pelagic in laboratory conditions from 23 to 35 days (Culliney 1974). The 

 length of this stage in natural conditions is unknown, since the planktonic 

 larvae of this species of scallop have never been positively identified in the 

 ocean. 



After approximately a month the larvae undergo metamorphosis and develop eye 

 spots, a foot, and byssus (Culliney 1974). Settling response, according to 

 Culliney (1974), is related to contact with a solid body and is not highly 

 specific as to type. Natural populations of juvenile scallops have been found 

 attached by their byssus to the branches of a bryozoan (Baird 1953), to a 

 hydrozoan, to amphipod tubes, and to grains of sand (Larsen and Lee 1978). 



Natural mortality of juvenile scallops is high according to surveys in 

 February and May on Georges Bank, which indicated a sharp drop in abundance of 

 live scallops (Larsen and Lee 1978). 



Baird (1967) reports that scallops grow to 0.08 inch (2 mm) in their first 

 winter and Larsen and Lee (1978) report a growth of 0.05 inch (1.3 mm) in the 

 5 months after settlement on Georges Bank. These growth rates are slower than 

 those observed on and around navigational buoys in the Nantucket Shoals area, 

 0.08 to 0.5 inch (2 to 14 mm). The adult size generally ranges from 2 to 4.9 

 inches (50 to 125 mm; Baird 1967). 



The scallop feeds on phytoplankton and suspended detritus, which it filters 

 through its gills. 



Habitat Preferences 



In Maine, scallops of commercial size are most abundant in saline waters (>30 

 ppt) at depths of approximately 20 m (66 feet; personal communication from D. 

 F. Schick, Maine Department of Marine Resources, Augusta, ME; April, 1978). 

 In the southern part of the range, i.e., Long Island to North Carolina, the 



12-11 



10-80 



