Conservation of Giant Clams (Bivalvia: Cardiidae)

Abstract

Giant clams are conspicuous bottom-dwellers of the tropical Indo-Pacific coral reefs. To date, there are 12 recognized species divided into two genera (Hippopus and Tridacna) in the subfamily Tridacninae. Because of their large body sizes and shallow distributions, giant clams are readily found and collected, and have been a reliable traditional coastal resource (food and shells) throughout their geographic range. Unfortunately, the unsustainable levels of exploitation, coupled with loss of habitats, pollution and climate change, have threatened the survival of wild giant clam populations. Due to the nature of their reproduction (e.g., late reproductive maturity and broadcast spawning), giant clam populations are highly sensitive to stock depletion, which reduces fertilization success and subsequently, recruitment rates. To better safeguard the remaining giant clam populations, conservation actions such as listing in the CITES Appendix II and the IUCN Red List of Threatened Species have contributed to stemming further declines, and local laws have helped to manage subsistence fishing practices and curtail illegal fishing. Mariculture also has a complementary role in the conservation of giant clams, as it can produce large numbers of individuals to assist in the restoration of depleted populations. In addition to these existing measures, it is important to meaningfully engage with all stakeholders (e.g., fishers, traders, and public) on the ecological value of giant clams and consequences of overexploitation to bring about changes in attitude and lead to sustainable fishing practices.