Baited Remote Underwater Video Surveys to assess relative abundance of sharks and rays in a long standing and remote marine protected area in the Arabian Gulf

Abstract

Marine Protected Areas (MPAs) are increasingly advocated for the protection of key functional groups like elasmobranchs (sharks and rays). However, substantial uncertainty remains regarding which species can benefit from MPAs, crucial information to support policy and management plans. Using Baited Remote Underwater Video Surveys (BRUVS), a study was conducted on Sir Bu Nair Island in the United Arab Emirates encompassing a range of depths and habitat types within the MPA borders. A total of 96 deployments with 117 video hours recorded were analysed to assess the diversity, relative abundance and habitat associations of elasmobranchs. Surveys recorded 40 elasmobranchs including two species of sharks and seven species of rays. Overall, catch per unit effort for elasmobranchs was slightly higher overall, lower for sharks, and higher for rays compared to a similar study using BRUVS across United Arab Emirates waters. Two reef-associated species in early life stages, blacktip reef shark (Carcharhinus melanopterus) and Halavi guitarfish (Glaucostegus halavi) listed as Near Threatened and Critically Endangered on the IUCN Red List of Threatened Species respectively showed the highest frequency of occurrence of species representing 44.4% of all sightings. These results show the value of this MPA in protecting critical habitats for elasmobranchs while suggesting its limitation in protecting adult life stages and other elasmobranchs with wider ranging movements that are likely threatened by fishing in waters adjacent to the MPA. This study provides critical information to support the development of a Sir Bu Nair management plan and highlights further research needs around the island. Finally, it reinforces the need of additional management measures to protect and promote the recovery of elasmobranchs in the United Arab Emirates and broader Arabian Gulf.