Bay scallop, continued 



commercial landings are coastal areas of Massachu- 

 setts, Rhode Island, New York, North Carolina, and the 

 gulf coast of Florida (Heffernan et al. 1988, Rhodes 

 1991). 



In the United States, Argopecten irradians is consid- 

 ered to include three subspecies: A. i. irradians, rang- 

 ing from Cape Cod to New Jersey; A. i. concentricus, 

 New Jersey to the Chandeleur Islands, east of the 

 Mississippi River; and A. i. amplicostatus, Galveston 

 Bay to Tuxapan, Veracruz, Mexico (Andrews 1981, 

 Fay etal. 1983). 



Within Study Area : Along the Florida Gulf coast, bay 

 scallops are most abundant from Pepperfish Keys, 

 south of Steinhatchee, north and westward to St. 

 Andrew Bay (Arnold pers. comm.). Populations are 

 scattered in the northwestern Gulf, but become more 

 common in the western Gulf. In Texas, the bay scallop 

 is most abundant in bays of the southern coast where 

 the salinities are generally higher and seagrass mead- 

 ows are extensive. The subspecies Argopecten 

 irradians concentricus ranges from Key West, Florida 

 to the Chandeleur Islands of Louisiana (Broom 1 976). 

 Argopecten irradians amplicostatus ranges from 

 Galveston, Texas to the Laguna Madre (Broom 1976, 

 Andrews 1981) (Table 5.01). 



Life Mode 



Fertilized eggs are demersal (Belding 1910). Early 

 larval stages are pelagic and planktonic. Late larval 

 stages are epibenthic. Juveniles up to 20-30 mm in 

 length attach to a surface suspended off the bottom by 

 byssal threads (Sastry 1 965). Adults and juveniles >30 

 mm in length are epibenthic, sometimes motile, and 

 gregarious (Belding 1910, Gutsell 1 930, Marshall 1 947, 

 Sastry 1 962, Robert 1 978, Peters 1 978, Fonseca et al. 

 1984). 



Habitat 



Type : All life stages are estuarine, and marine in 

 nearshore waters, occurring in high salinity (euhaline 

 to polyhaline) waters. Bay scallops are typically sub- 

 tidal, but may be exposed during especially low tides 

 (Rhodes 1991). Collections have been recorded at 

 depths from to 10 m and a maximum of 18 m. They 

 are most abundant in waters from 0.3 to 0.6 m at low 

 tide (Marshall 1960, Sastry 1962, Thayer and Stuart 

 1974, Peters 1978, Robert 1978, Fay et al. 1983, 

 Fonseca etal. 1984). Larvae inhabit the water column 

 while searching for a settlement site (Sastry 1 965). At 

 settlement the young scallop attaches epifaunally to a 

 surface suspended off the bottom (rock, seagrass, 

 algae, rope) by means of byssal threads (Belding 

 1910). At 20 to 30 mm in length the juvenile scallop 

 settles to the bottom, beginning a demersal existence 

 that continues through the adult stage (Castagna 1 975). 



14 



