Restocking of giant clams: Progress, problems and potential

Throughout much of the Indo-Pacific, populations of giant clams (Tridacnidae) have been depleted to the point where they have limited potential for replenishment. Restocking with juveniles reared in hatcheries offers the most rapid way to re-establish these stocks. A multi-national, collaborative research effort has resulted in reliable methods for the production of juvenile giant clams; the development of protocols for restocking these species to maintain the genetic diversity of wild populations: measures to reduce the risks of transferring predators, diseases, and pathogens; and the restocking of giant clams in 16 countries. However, with the exception of a major programme in Okinawa, Japan, large numbers of cultured giant clams have yet to be established in the wild. Major impediments to restocking have been the need to protect juveniles from predation for up to 3 years and the poaching of transplanted giant clams. It is now evident that the economic burden of producing 3-year-ord animals can be overcome by coupling restocking with farming. In such programmes, giant clam farmers nurture 2 to 5% of their stock for placement on coral reefs. Poaching can also be reduced by restocking giant clams in protected areas. Research is now needed to identify how to transplant mature clams to optimize recruitment.