Species composition, abundance and conservation status of some economically important macrobenthic invertebrates in Pagasa island, Kalayaan, Palawan, Philippines

Abstract

Pag-asa Island is the largest and the only civilian inhabited island in the Kalayaan Island Group (KIG) in the West Philippine Sea. The waters around these islands are important fishing grounds; however, little information is available on the status of macrobenthic invertebrates within the vicinity of the island. In this study, we assessed the species composition, abundance and conservation status of some commercially important macrobenthic invertebrates in shallow reefs and seagrass beds surrounding the island. The sampling was conducted during day time of dry season for 6 days (May 9-14, 2018) through wading, snorkelling and scuba diving which recorded a total of seven species, mostly bivalves and echinoderms. Bivalve species included the giant clams Tridacna maxima (Röding, 1798) and Tridacna crocea Lamarck, 1819; echinoderms included Bohadschia argus Jaeger, 1833, Bohadschia vitiensis (Semper, 1868), Holothuria atra Jaeger, 1833, Holothuria leucospilota (Brandt, 1835) and Tripneustes gratilla (Linnaeus, 1758). These species occurred more abundantly in seagrass beds than in coral reefs, ranging from 46.7–1,346.7 ind.ha-1. Most of the species were of “Least Concern” status according to International Union for Conservation of Nature (IUCN) Red List. The absence of previously reported high valued species in the surveyed sites, such as topshell Rochia nilotica (Linnaeus, 1767) and lobsters Panulirus versicolor (Latreille, 1804) could be an effect of unregulated harvesting. Effective resource management in this part of KIG is needed to allow the recovery of reduced populations and ensure food security for the inhabitants of the island.