FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

The giant clam (Tridacnidae) is the largest bivalve in the world and used to be one of the health index species of a coral reef ecosystem in sea areas. In order to evaluate the distribution and density of giant clams around Green Island, Taiwan, and to analyze the protective effect of conservation areas on giant clams, a transect belt survey method was implemented in 2015 and 2016. Twenty-four stations around Green Island conducted underwater surveys in order to obtain the basic distribution and density of giant clams around Green Island. The results showed that the average density of giant clams was 1.5 clams/100m2 in 2016, which was lower than the 2.5 clams/100m2 density reported for 2015. The dominant species was Tridacna maxima, which accounted for over 70% of the clams observed, followed by Tridacna noae at about 20%. The Shilang Conservation Area has a high density of and is a hot zone for sexually mature shellfishes with shells longer than 15 cm. The Shilang Conservation Area is effective at protecting giant clams, but the Guiwan Conservation area was found to have a low density of giant clams. Thus, its protective effect is insufficient, and so additional advocacy for conservation shall be implemented. The findings of this study will help conserve local giant clam resources and can be used as reference data for long-term monitoring of marine habitats and the health of coral reefs in the future for the sustainable utilization of ocean resources.