Tridacnidae's habitat preferences in Bama waters, Baluran National Park, Situbondo Regency, East Java, Indonesia

The existence of clams on a different substrate indicates that not all types of substrates are tolerated by certain types of clams. Clams naturally attach and sink their shells in coral reefs. The status of clams {Tridacnidae) which are endangered makes this biota included in the CITES Appendix II record. The distribution of clams in the world counts as many as 9 species and 7 of them are spread in Indonesian waters, including the Bama waters of Baluran National Park. This study aimed to determine the community structure and substrate preferences for clam shells in Bama Waters, the Baluran National Park conservation area. The location for data collection was determined by random sampling, during the East Monsoon season, namely August 2022. Habitat analysis used the Ivlev Electivity Index which was displayed on a diagram for each substrate type. The results revealed the presence of 4 types of clam populations: with various densities: Tridacna crocea (0.52 ind m-2), Tridacna maxima (0.18 ind m-2), Tridacna squamosa (0.14 ind m2) and Hippopus hippopus (0.03 ind ha-1). The chemical abnormality index belongs to the low category, ranging from 0.41 to 0.66. Based on the habitat analysis based on the Ivlev electivity index, it was inferred that T. squamosa and H. hippopus prefer the rubble substrates with (E) 0.32 and 0.53, respectively, while T. crocea prefers rock substrate with an Ivlev Electivity Index of 0.77 and T. maxima prefers hard corals with an Ivlev Electivity Index of 0.01-0.22.