Bay scallop, continued 



etal. 1989, Prescott 1990). 



Personal communications 



Factors Influencing Populations : A probable limiting 

 factor for distribution in the southern range of the bay 

 scallop is its increased metabolic rate in this area 

 associated with the higher temperatures of this region 

 and a decreased food supply that causes a net loss of 

 available energy for reproduction (Barber and Blake 

 1 983). Excessive turbidities and current velocities can 

 inhibit growth and reproduction (Kirby-Smith 1 972, Fay 

 et al 1983). Bay scallops living on soft mud substrate 

 are subject to burial during events that increase current 

 velocity (Tettelbach et al. 1 990). Seagrass provides a 

 substrate for attachment by bay scallop larvae, and the 

 abundance of this species is influenced by its presence 

 (Thayer and Stuary 1974, MacKenzie 1989). Destruc- 

 tion of seagrass areas results in decreased abundance 

 of this species. Smith et al. (1 988) have demonstrated 

 that transplanted seagrass does not serve as a quality 

 habitat with apparently greater loss due to predation 

 and/or transport in the transplanted seagrass as com- 

 pared to the natural seagrass. Blooms of red tide algae 

 in sufficient concentrations can result in conditions 

 toxic to adult and larval bay scallops (Summerson and 

 Peterson 1 990). Nuisance blooms of algae can affect 

 bay scallops by altering feeding rates. These species 

 are often low in nutritive value causing poor recruitment 

 and settlement of the bay scallop due to the algae's 

 inability to suport adequate larval growth (Nelson and 

 Siddal 1988, Summerson and Peterson 1990). Popu- 

 lation sizes are subject to a large degree of variation 

 within the year because of the bay scallop's short life 

 span and semelparous reproductive cycle (Fay et al. 

 1983, Nelson and Siddall 1988, MacKenzie 1989). 

 Bay scallops generally spawn only once during their 

 lives when they reach the end of their first year. 

 Although two year old animals occur rarely, popula- 

 tions are almost entirely composed of only one year 

 class, upon which the following year class is com- 

 pletely dependent. Unfavorable conditions that result 

 in poor larval recruitment in any given year may there- 

 fore lower abundance the following year. Low DO 

 episodes may have long-term population effects due to 

 the bay scallops semelparous reproductive cycle as 

 well as effecting short-term mortality (Voyer 1992). 

 Predation by visually oriented carnivores may be exert- 

 ing selection pressures on populations of bay scallops 

 resulting in shell color polymorphism (Elek and 

 Adamkewicz 1990). Known parasites include the pea 

 crab, Pinnotheres maculatus (Kruczynski 1972). Bay 

 scallops parasitized by this organism display stunted 

 growth rates and reduced weights. Another parasite is 

 the polychaete Polydora which can penetrate bay 

 scallop shells and sometimes produce blisters on the 

 interior shell surfaces (Rhodes 1991). 



Arnold, William S. Florida Marine Research Inst., St. 

 Petersburg, FL. 



Castiglione, Marie C. NOAA National Marine Fisheries 

 Service, Galveston, TX. 



Shelfer, L.W. Florida Marine Patrol, Tallahassee, FL. 



References 



Andrews, J. 1981. Texas Shells, A Field Guide. 

 University of Texas Press, Austin, TX, 175 p. 



Barber, B.J., and N.J. Blake. 1983. Growth and 

 reproduction of the bay scallop, Argopecten irradians 

 (Lamarck) at its southern distributional limit. J. Exp. 

 Mar. Biol. Ecol. 66:247-256. 



Belding, D.L. 1910. The scallop fishery of Massachu- 

 setts. Mass. Dept. Cons. Div. Fish. Game, Mar. Fish. 

 Ser. No. 3, 51 p. 



Bricelj, V.M..J. Epp, and R.E. Malouf. 1987. Intraspe- 

 cif ic variation in reproductive and somatic growth cycles 

 of bay scallops Argopecten irradians. Mar. Ecol. Prog. 

 Ser. 36:123-137. 



Broom, M.J. 1976. Synopsis of biological data on 

 scallops. FAO Fisheries Synopsis No. 114. Food and 

 Agriculture Organization of the United Nations, Rome. 

 44 p. 



Castagna, M., and W. Duggan. 1971. Rearing of the 

 bay scallop, Aequipecten irradians. Proc. Natl. Shell- 

 fish. Assoc. 61:80-85. 



Castagna, M. 1975. Culture of the bay scallop, 

 Argopecten irradians in Virginia. Mar. Fish. Rev. 

 37:19-24. 



Chipman, W.A. 1954. On the rate of water propulsion 

 by the bay scallop. Proc. Natl. Shellfish Assoc. 45: 1 36- 

 139. 



Cooper, R.A., and N.Marshall. 1963. Condition of the 

 bay scallop, Argopecten irradians, in relation to age 

 and the environment. Chesapeake Sci 4:126-134. 



Crenshaw, J.W., P.B. Heffernan, and R.L. Walker. 

 1991. Heritability of growth rate in the southern bay 

 scallop, Argopecten irradians concentricus. J. Shell- 

 fish Res. 10(1): 55-63. 



Davis, R.L. , and N. Marshall. 1961. The feeding of the 

 bay scallop. Proc. Natl. Shellfish. Assoc. 52:25-29. 



17 



