scallop (Waller, 1969). At Bermuda, however, 

 calico scallops were found in an almost complete- 

 ly enclosed sound (Neumann, 1965; Kirby-Smith, 

 see footnote 3). 



Environment 



Factors that probably influence distribution 

 and/or growth of the calico scallop include cur- 

 rents, temperatui-es, salinities, substrates, and 

 food supply. 



Currents may be of primary importance in 

 controlling distribution of scallop larvae and, ul- 

 timately, the positioning of the scallop beds. 

 Kirby-Smith (1970) suggested that North Car- 

 olina populations of scallops may be at least par- 

 tially maintained by larvae transported from 

 Florida scallop grounds via the Gulf Stream. 

 The greatest concentrations of calico scallops are 

 found near coastal prominences such as Cape 

 San Bias and Cape Kennedy, Fla.; and Cape 

 Lookout, N.C. Bullis and Cummins (1961) sug- 

 gested that the Cape Kennedy projection causes 

 "interruption and eddying" that produces "re- 

 petitive settling of scallop larvae . . . creating 

 a permanent resource." The scallop beds are 

 generally distributed along the flow lines of cur- 

 rents (National Marine Fisheries Service)' and 

 are thus oriented parallel to the coastline. On 

 the Cape Kennedy grounds, scallops are irreg- 

 ularly distributed but "occur in long narrow 

 bands" (Bullis and Cummins, 1961). Some 

 bands or beds are more than 800 m long and 

 several hundred meters wide (Roe, Cummins 

 and Bullis, 1971). An elliptical-shaped bed 

 16 km long near Cape Lookout was reported by 

 Cummins, Rivers, and Struhsaker (1962). A 

 bed 16 km long and 8 to 16 km wide near Cape 

 San Bias was reported by Bullis and Ingle 

 (1959). 



The importance of temperature in controlling 

 reproduction and survival, and thus geographic 

 distribution, of marine bivalves, including the 

 calico scallop, was emphasized by Pulley (1952). 

 Waller (1969) suggested that calico scallop dis- 



tribution is limited primarily by temperature. 

 According to Parker (1956), the calico scallop 

 is one of a faunal assemblage in the northern 

 Gulf of Mexico that inhabits waters deep enough 

 to avoid winter cooling. Bottom temperatures 

 associated with calico scallops range from 9.9°C 

 (Merrill see footnote 4) to 33.0°C (Waller, 

 1969). Vernberg and Vernberg (1970) ob- 

 served, however, that calico scallops collected 

 near the northern end of their range, off North 

 Carolina, did not survive 48-hr exposure to lab- 

 oratory water temperatures of 10°C, and have 

 "tropical affinities." Near Cape Lookout, a cal- 

 ico scallop bed was "usually dominated by Car- 

 olinian coastal waters" (Wells, Wells, and Gray, 

 1964), although bottom temperatures in this 

 area show considerable fluctuation in conjunction 

 with winter and spring meanders of the Gulf 

 Stream (Grassle, 1967). North of Cape Hat- 

 teras, the existence of calico scallops may coin- 

 cide with a mass of relatively warm water (Mer- 

 rill, see footnote 4). 



Salinities from areas where calico scallops 

 occur are fairly stable and range from about 31 

 to 37;:*', (Anderson, Moore, and Gordy, 1961; 

 Hulings, 1961; Grassle, 1967; Pequegnat and 

 Pequegnat, 1968). 



The substrates required or preferred by the 

 calico scallop may vary with scallop size. Young 

 scallops up to about 25 mm in height are found 

 byssally attached to whole or broken mollusk 

 shells. Although commonly attached to dead 

 scallop shells (Commei'cial Fisheries Review, 

 1962) , they are also found on dead shells of other 

 mollusks (Allen)' and on live scallop shells 

 (Wells, Wells, and Gray, 1964). Shells may be 

 necessary for successful settlement of small scal- 

 lops (Kirby-Smith, 1970) , but spat may com- 

 pete with adults for optimum substrate (Roe, 

 Cummins, and Bullis, 1971). 



Larger scallops, usually unattached, are re- 

 ported from bottoms composed of hard sand 

 (Rivers, 1962a), sand and shell (Sastry, 1962; 

 Cummins, Rivers and Struhsaker, 1962), quartz 

 sand (Hulings, 1961), smooth sand-shell-gravel 

 (Struhsaker, 1969a), fairly clean, medium- 



' National Marine Fisheries Service (in cooperation 

 with state, industry, and university groups in Florida, 

 Georgia, South Carolina, and North Carolina). 1971. 

 Joint plan for the calico scallop fishery. Unpublished 

 report, 115 p., filed at the National Marine Fisheries 

 Service, Southeast Fisheries Center, Miami Laboratory, 

 Miami, Fla. 33149. 



' Allen, D. M. 1971. Ecology of the calico scallop, 

 Argopecten gibbus, as determined by spat monitoring. 

 Unpublished manuscript filed at the National Marine 

 Fisheries Service, Southeast Fisheries Center, Miami 

 Laboratory, Miami, Fla. 33149. 



