grained quartz sand (Hulings and Hemlay, 

 1963), and sand and dead shell (Drummond, 

 1969). Grassle (1967) found calico scallops as- 

 sociated with a mud sediment that contained a 

 high percentage of quartz and shell. 



Essentially nothing is known concerning the 

 food requirements of the calico scallop. This 

 subject was discussed by Kirby-Smith (1970), 

 who suggested that zooplankton may be an im- 

 portant source of nutrition. Where scallop 

 abundance is greatest, plankton concentration 

 may be high, since upwelling in the general areas 

 of Cape San Bias, Cape Kennedy, and Cape Look- 

 out is reported respectively by Gaul, Boykin, and 

 Letzring (1966), Taylor and Stewart (1959), 

 and Wells and Gray (1960). 



On the Cape Kennedy grounds, the locations 

 of individual scallop beds vary from year to year 

 and probably are determined by environmental 

 conditions which control setting and survival of 

 larval scallops (National Marine Fisheries Ser- 

 vice, see footnote 7). Personnel of the Miami 

 Laboratory are attempting to relate scallop 

 abundance and growth to substrate types, and 

 to water temperatures and currents now being 

 monitored on the Cape Kennedy grounds. 



Relative Abundance 



The relative abundance of calico scallops var- 

 ies between areas. The greatest known abun- 

 dance is located off the Florida east coast near 

 Cape Kennedy, with lesser concentrations near 

 Cape Lookout, N.C., and in the northeastern 

 Gulf of Mexico near Cape San Bias, Fla. Con- 

 centrations were also reported from the eastern 

 Gulf of Mexico between Sanibel Island and Dry 

 Tortugas (Bullis and Ingle, 1959; Carpenter, 

 1967). Generally fewer scallops are found else- 

 where within the calico scallop range. 



Abundance also varies within areas. Young 

 calico scallops in the northeastern Gulf of Mex- 

 ico were more abundant on fouling arrays an- 

 chored 18 km offshore in 31 m than on those an- 

 chored 3 km offshore in 19 m and 40 km offshore 

 in 46 m (Pequegnat and Pequegnat, 1968) . Vari- 

 ations in average abundance of commercial size 

 scallops off the Florida east coast for 1960 to 1966 

 were given by Drummond (1969) as follows: 

 Scallops were most abundant on the southern 

 portion of the grounds in 28 to 65 m (Fig. 3). 

 At these depths, the average rate of catch with 



a 2.4-m (8-ft) scallop dredge ranged from 3.9 

 to 12.8 bu per hour. For these catches, 1 bu 

 equaled 36 kg (80 lb.) of scallops in the shell. 

 The rate of catch was highly variable; within 

 one area, catches ranged from to 54 bu per 

 hour. Within a scallop bed, also located off the 

 Florida east coast, average scallop densities were 

 about 43 individuals per square meter (4 per 

 square foot) (Cummins, 1971), but densities 

 may exceed 108 per square meter (10 per square 

 foot) (Roe, Cummins, and Bullis, 1971). 



Abundance varies with scallop size, although 

 this is poorly documented. Dense concentrations 

 of scallop spat are caught in spat traps, e.g., 107 

 individuals per liter (3,000 per cubic foot) per 

 2-month period (Allen, see footnote 8). While 

 density of spat set naturally on the bottom is 

 probably much less, catches of small scallops with 

 dredges at times exceed catches of large indi- 

 viduals (Commercial Fisheries Review, 1968). 



Abundance varies both seasonally and annu- 

 ally. Monthly changes in scallop abundance by 

 area off the Florida east coast were shown by 

 Drummond (1969). On these grounds, abun- 

 dance (as measured by catch rate) was highest 

 from September to December in 1967 and 1968 

 (Roe, Cummins, and Bullis, 1971). Abrupt 

 yearly differences in scallop abundance have been 

 reported for the grounds off North Carolina 

 (Cummins, 1971; Lyles, 1969) and in the north- 

 eastern Gulf of Mexico (Bullis and Ingle, 1959; 

 Hulings, 1961). 



Reproduction 



The calico scallop is hermaphroditic. When 

 this species spawned in the laboratory, the sperm 

 and eggs (in that order) were ejected sepa- 

 rately into the water where fertilization took 

 place (Costello et al.).° 



We observed, based on gonadal color (see be- 

 low) , that some calico scallops as small as 19 mm 

 in height are ripe, which indicates either ripeness 

 at a very early age or that these small scallops 

 are older than suspected (see footnote 2). Roe, 

 Cummins, and Bullis (1971) stated that spawn- 

 ing of the calico scallop "is related to age rather 



" Costello, T. J., J. H. Hudson, J. L. Dupuy, and S. 

 Rivkin. 1971. Larval development of the calico scallop, 

 Argopecten gibbus. Unpublished manuscript filed at the 

 National Marine Fisheries Service, Southeast Fisheries 

 Center, Miami Laboratory, Miami, Fla. 33149. 



