A catalogue of coral reef fishes from the Sugud Islands Marine Conservation Area, Sabah, Malaysia.

This study provides the first comprehensive checklist of coral reef fishes from the Sugud Islands Marine Conservation Area (SIMCA), Sabah, Malaysia, a strictly no-take marine protected area (MPA) in the Sulu Sea. Based on underwater surveys and intercepted trawl landings conducted between 2006 and 2023, we recorded 622 species representing 73 families. The most species-rich families were Labridae (74 species), Pomacentridae (61), and Gobiidae (57), together with six other families that collectively comprised 55% of all records. The Coral Reef Fish Diversity Index (CFDI) estimated a potential richness of 647 species. Thirty-six species are listed on the IUCN Red List, including four Critically Endangered elasmobranchs, with Rhina ancylostoma (Bowmouth Guitarfish) representing the first record for SIMCA. Eight species are listed under CITES Appendix II, and three are regulated by Malaysian law. Long-term monitoring was essential for detecting cryptic, nocturnal, and wide-ranging taxa that would likely have been overlooked in short-term studies. These results demonstrate the value of sustained protection in maintaining high species diversity and provide a baseline for future biodiversity management and conservation planning in Malaysia's Coral Triangle waters.