Bivalve enhancement and restoration strategies in Florida, USA

In Florida, U.S.A. populations of recreationally and commercially important bivalve molluscs are stressed by a variety of factors, including habitat degradation, overfishing and development. Bivalves such as the bay scallop, Argopecten irradians, and the hard clam, Mercenaria spp., are uniquely positioned to benefit from restoration and enhancement activities because of the physical setting in which they live or because of recent efforts to restore habitat. For bay scallops, a major restoration effort has been implemented on the west coast of Florida. Adult scallops are collected from the target site and spawned in the laboratory. The offspring are cultured in ponds until they reach an average shell height of approximately 30 mm and then are planted in cages at the target site from which the parents were collected. Parents and offspring are genetically monitored, as are new recruits sampled at a variety of sites along the coast. The ultimate goal of this restoration program is to create concentrated patches of spawners that will supply recruits to west Florida seagrass beds. For hard clams, three different strategies are being tested to determine the most ecologically and economically feasible approach to use to enhance harvestable clam populations. Hard clams are occasionally abundant in the Indian River lagoon on the east central coast of the state, but transportation causeways fragment the lagoon into a series of basins that are largely isolated from one another. At any time, only a subset of the basins that compose the lagoon may be environmentally suitable for supporting the sensitive larval and juvenile stages of hard clams, and the members of that subset change constantly as environmental conditions change in the lagoon. Transplanting spawner stock, seeding juveniles under a variety of protective treatments, and injecting fertilized eggs directly into the lagoon are each being tested for their effectiveness in exploiting environmentally appropriate conditions and producing successful settlement events. Each strategy is being tested for its ecological and economic suitability, and the most appropriate strategy will be implemented in an effort to maintain clam abundance at a level where licensed clammers in the Indian River region can realize a minimum income from the fishery, even when naturally recruiting clam stocks are depleted.