Shellfish aquaculture is the farming (i.e., cultivation and harvest) of aquatic invertebrates, such as oysters, clams and mussels. Cultivation implies involvement in the rearing process to enhance production, such as regular stocking and protection from predators. The systems used to farm shellfish have evolved from purely beach to technology-based systems that are designed for specific species and farming sites.
Shellfish begin their lives as larvae that mature into seed and/or juvenile animals. The farm cycle begins with the collection of larvae, which may be gathered in the wild or produced from hatchery broodstock (depending on the species and location).
*Clam larvae are kept in hatchery tanks where they transform into seed.
*Mussel larvae transform to juvenile animals.
*Scallop larvae settle and become juvenile animals.
*Oyster larvae are kept suspended in tanks by circulating water until they transform into seed.
Farmers acquire clam and oyster seed at various stages of its development – depending on the requirements of the tenure and farming operations. The seed is put into a nursery environment where it is nurtured into juvenile animals. Generally speaking, the juvenile animals then graduate to the growout phase of their development.
*Clams are spread on subtidal tenures where they burrow and mature to marketable size over a period of two to four years.
*Mussels are relocated to deepwater tenures where they are suspended in mesh socks to mature to marketable size over a period of 18 to 36 months.
*Scallops are transferred to deepwater tenures where they are suspended in a mesh bag or tray (suspension culture) or are seeded on the ocean floor (bottom culture). Maturation to marketable size takes six to 36 months in suspension culture and an additional 24 to 36 months for bottom culture.
*Oysters are frequently moved to a floating upwelling system (called a flupsy). Ocean water is circulated through the flupsy and juvenile animals, kept in trays, are able to grow to a larger size. When they are large enough, the young oysters are moved to be reared in a growout system. The most common growout techniques are raft, longline and intertidal.