Diversity and Abundance of Sea Cucumbers in Selected Areas of Mindanao, Philippines

Abstract

The Philippines is a “hotspot” for sea cucumbers in Asia, where decades of lack of management led to declining fisheries and biodiversity. Sea cucumbers have been widely gathered in Mindanao; however, only a few studies provide updates on sea cucumber diversity and abundance. To supplement this scant information, a survey was conducted in the eight chosen sites of the five major sea cucumber fishing grounds aimed at assessing the status of sea cucumber diversity, density, and average sizes. Line-transect surveys carried out from May–August 2021 found 22 sea cucumber species across eight sites – including two high-value species, Actinopyga lecanora, and Holothuria scabra. The most common species are Actinopyga echinites and Stichopus horrens considered of medium-value and found in all surveyed sites. H. scabra and A. echinites are listed in the International Union for Conservation of Nature (IUCN) red list as “endangered” and “vulnerable,” respectively, whereas the remaining sea cucumbers are either data deficient or least concerned. Tambunan MPA (marine protected area) in Tabina had the highest sea cucumber density (3,560 ind. ha–1) during daytime sampling, whereas Solar in Olutanga (3,220 ind. ha–1) during nighttime. High relative abundance of low to no commercial value holothurians were recorded during daytime and medium-value species during nighttime. The low-value Holothuria atra is the most abundant (27.2%) sea cucumber. Shannon diversity index revealed low diversity during daytime (0.13–1.43), whereas Bacayawan in Dimataling and Passig Islet in Sta. Cruz had a Shannon diversity value of > 1.5 in the nighttime. Average sizes of sea cucumbers in the surveyed sites are generally small (< 20 cm), except for a few species. The results of the study serve as baseline information for the formulation and implementation of site-specific local policies and management programs for the sustainability and conservation of sea cucumber stocks.