Substrate type preferences and species density of Echinometra Mathaei in the intertidal ecosystem of Bilik Coastal Baluran National Park

Sea urchins is members of phylum Echinoderms and class Echinoidea. One species of sea urchin is Echinometra mathaei. Availability of information on substrate preferences and density is urgently needed in conservation of E. mathaei. Data was collected using the road sampling method, which is a trip along the coast along the shore to the edge (farthest low tide area) or vice versa until it covers the entire Bilik Beach area at low tide. Analysis of substrate preference selection based on substrate type for tropical marine biota and analysis population density of E. mathaei. The substrate preference of E. mathaei in intertidal ecosystem of Bilik Coastal was found in dead coral substrate (dead coral) with a percentage of 62.61%, on dead coral substrate overgrown with macroalgae (dead coral algae) with a percentage of 27.70% and on rock substrate (rock) with a percentage of 9.70%. The density of E. mathaei in Bilik Coastal TNB is low, namely < 1 individual/m2.