Spatial and Temporal Abundance of the reef gastropod Tectus niloticus (Gastropoda: Tegulidae) in Marine Protected Areas in Palawan, Philippines: Prospects for Conservation

Abstract

The unsustainable harvesting of the reef gastropod Tectus niloticus or ‘trochus’ for the production of ‘mother of pearl’ buttons have led to the collapse of its population and closure of its fishery in some countries. With the costly conservation measure involving the restocking of hatchery produced juveniles in partly protected reefs in the Philippines, this study assessed the abundance of trochus in three types of habitats of three Marine Protected Areas (MPAs) in Palawan, Philippines to document the status of its populations and to propose a more relevant conservation measure. Unguarded and continuously exploited MPAs in the mainland Palawan harboured the least numbers of trochus. By contrast, in effectively protected areas of the Tubbataha Reefs Natural Park (TRNP), densities were quite high with large trochus being abundant in three types of habitats. However, the densities declined the farther the site from the Ranger Station of TRNP. In permanent monitoring sites in TRNP, the abundance declined between 2006 and 2008, with slight recovering trends toward 2010. Sizes of sampled trochus at TRNP in 2008-2010 were significantly larger than in 2006. The presence of recruits at constantly fished MPAs at Palawan on the mainland could lead to population recovery if these areas are effectively spared from fishing for a longer period of time. Restored biodiversity in networks of MPAs could be highly beneficial to the ecosystem, the fisheries and economic sectors.