UTTAR PRADESH JOURNAL OF ZOOLOGY

Sea urchins are ecologically important benthic herbivores that influence community structure in tropical coastal ecosystems, yet baseline information on their assemblages remains limited in many parts of the Philippines. This study assessed the community structure, size structure and spatial distribution of sea urchins in the north-eastern coastal areas of Tablas Island, Romblon, Philippines. Sampling was conducted across 12 coastal stations in the municipality of San Agustin using 100-m belt transects covering 500 m² per station. A total of 442 individuals representing six species from four families were recorded. Tripneustes gratilla was the most abundant and most widely distributed species, occurring at all sampling sites, while Echinothrix calamaris was restricted to Long Beach. Species richness ranged from 2 to 6 species per station. Long Beach showed the highest diversity (H′ = 1.53) and the lowest dominance, whereas Poblacion exhibited the highest dominance (D = 0.64). Evenness was generally high in several stations, reaching 0.99 in Cawayan, Sugod, Doña Juana, Lusong, and Hinugusan. Mean test diameter ranged from 31.43 mm in Diadema setosum to 64.16 mm in E. calamaris, while the relatively small mean size of T. gratilla (40.48 mm) suggests possible size-selective harvesting pressure. Overall, the north-eastern coast of Tablas Island supports a moderately diverse but potentially sensitive to exploitation sea urchin assemblage, highlighting the need for continued monitoring and site-based conservation and fisheries management measures.