Abundance of Tridacna (Family Tridacnidae) at Seribu Islands and Manado Waters, Indonesia

Giant clam, as a protected marine species, has been exploited massively in many regions in Indonesia. This has lead to the rapid extinction of the giant clam natural population. The purpose of the research is to obtain the abundance status of giant clam species in several island in Kepulauan Seribu and surroundings waters of Manado. Surveys were done by using the modification of Line Intercept Transect (LIT) methods. A hundred meter length of transect line were drawn, in depth of 5 meter and paralleled to the coast line. The observations were made in 2.5 meter to the left and right of the transect line. The results showed, there were total number of clams found at Seribu Islands and Manado waters were 106 and 61 individual, respectively. The average density in Seribu Islands were T. squamosa: 0.026 indv/m², T. maxima: 0.016 indv/m², and T. crocea: 0.028 indv/m², and in Manado were T. squamosa: 0.021 indv/m², T. maxima: 0.0005 indv/m², T. crocea: 0.0085 indv/m² and T. gigas: 0.002 indv/m². These results showed that the density of giant clams in both places were found to be lower than other places in Indonesia and abroad. Based from the shell measurements on both locations, only T. crocea were suspected have reached its hermaphrodite phase, while T. gigas and most of T. squamosa and T. maxima were about to reached male gonad maturity phase. The most dominant substrate for the giant clam were the Dead Coral Algae (DCA) and the coral covered.