Characteristics of a previously undescribed fishery and habitat for Manta alfredi in the Philippines

Abstract

Seven species of mobulid rays occur in the Philippines, six of which, including the Giant Manta Ray (Manta birostris) are caught directly or indirectly. In the Bohol Sea, mobulids have been fished since at least the nineteenth century yet the extent is not well-understood. A second species of manta, Manta alfredi was taxonomically resurrected in 2009 and also only recently been confirmed to occur in the Philippines. This study aimed to identify and describe the presence of and fishery for M. alfredi in a previously unknown area of occurrence in the Philippines. Key informant interviews, observation of catch landings, and tissue sample collection were conducted in a fishing village off Dinagat Island. Based on morphological examination and through DNA barcoding using the mitochondrial DNA CO1 gene of tissue samples it was verified that the species targeted in this area is the reef manta ray, Manta alfredi. Local ecological knowledge of the fishers provided important information on the extent and characteristics of the fishery. This relatively recent ray fishery in the Surigao Strait is the source of mobulids during the off-fishing season in Bohol with fishers from this area transporting and selling their processed catches to Bohol. The description of this fishery and habitat for the reef manta ray in the Surigao Strait is important in the understanding of the status of the species in the Philippines and in designing a management framework.