Aquaculture of the Florida Bay scallop, Argopecten irradians concentricus , in Tampa Bay, Florida, USA, an urban estuary.

Abstract

Abstract Bay scallop (Argopecten irradians) populations along the east coast of the USA once supported both commercial and recreational fisheries. Since the 1950s, many of the local populations have collapsed. Both natural and anthropogenic factors, including hurricanes, red tide events, loss of habitat and overfishing, can result in large fluctuations in bay scallop populations. Urban estuaries that once supported bay scallop populations have been especially affected, and are slow to recover even if the water quality in the estuary is improved since natural linkages among local populations may be disrupted, for instance, preventing the transport of larvae. Tampa Bay is an example of an urban estuary that has lost its natural bay scallop population. Even though water quality conditions have greatly improved in recent years, bay scallops have not returned. A bay scallop hatchery, which utilizes seawater from Tampa Bay, has been in operation since 1990. In order to maintain genetic variability, adult scallops nearing reproductive maturity are collected in the early autumn from a population approximately 160 km north of Tampa Bay. These scallops are allowed to mature in cages suspended in Tampa Bay and are spawned in a recirculating system. Larval mortality through settlement (8-10 days) usually ranges from 10% to 50%, similar to that of other hatcheries. The larvae are fed on algae grown in sterilized Tampa Bay water. Settled spat are maintained in the recirculating system for 30-45 days, then transferred to fine mesh bags which are suspended about 1.0 m below the surface of the bay. Mortality and growth are monitored bi-weekly and scallops transferred to larger mesh containers as they grow. Throughout the autumn and winter, cumulative mortality is about 20%, and growth is 1.5-2.0 mm/week. By early spring the scallops reach 25 mm, and these are placed in suspended cages at a density of 200-250 individuals/m2. Mortality increases greatly in summer months due to high water temperatures and intense fouling. Nevertheless, more than 25% of the settled spat reach harvestable sizes of 45-50 mm by September. Surveys indicate that these scallops may be sold to processors dealing in the speciality market for US$0.25-0.30 each as a whole, in-shell product.