Abundance and diversity of holothuroids in shallow habitats of the northern Red Sea

Holothuroid sea cucumbers are vital members of Coral Reefs and associated marine habitats and provide vital ecological services. In the southern regions of the Red Sea their populations have been decimated by overfishing. The main objective of this study was to test the hypothesis that the northern part of the Red Sea serves as an ecological refuge for the species threatened farther to the south. Accordingly, populations of sea cucumbers in 4 shallow sites south of Eilat, Israel (29°33′00N 34°57′14E), were repeatedly surveyed from November 2013 to April 2014. Overall 11 species were observed in these shallow sites. Their abundance and diversity differed significantly between sites, but not temporally. In sites in marine protected areas, with an intact fringing reef, diversity was high, with Holothuria edulis and Bohadschia sp. being the most common species. In areas with higher human use and characterized by rubble and scattered corals, diversity was low, and Actinopyga bannwarthi was the most common species. The observed abundance and diversity did not support the refuge hypothesis. These findings are discussed in relation to other surveys of abundance and diversity in similar habitats.