Abstract
Data on the diversity and relative abundance of elasmobranchs (sharks and rays) in the Arabian Gulf have been limited to fishery-dependent monitoring of landing sites. Understanding the diversity and abundance of sharks and rays is, however, crucial to inform policy and management plans. Baited Remote Underwater Video Surveys (BRUVS) were conducted in 2015–2016 across the United Arab Emirates Arabian Gulf waters encompassing a range of depths and habitat types. Data from 278 BRUVS (757 hours soak time) were analysed to gather information on diversity, relative abundance, species distribution, and habitat associations. Surveys recorded 213 individuals from 20 species of sharks and rays at 129 stations. The frequency of occurrence of species usually discarded by fishers such as the Arabian carpetshark (Chiloscyllium arabicum) and stingrays (Himantura spp.) was high, accounting for 60.5% of observed elasmobranchs. Despite the large survey area covered and extensive sampling effort, the relative abundance of sharks and rays was low at 0.28 elasmobranchs per hour, 0.13 sharks per hour, and 0.15 rays per hour. This CPUE was reduced to one of lowest recorded abundance on BRUVS from around the world when removing the two discarded species from the analysis (0.11 elasmobranchs per hour). These results likely reflect the intense fishing pressure and habitat loss contributing to population declines of many elasmobranchs in the Arabian Gulf. Findings provide a baseline for future work and can support the design of conservation strategies for sharks and rays in the UAE.
Highlights
Beyond the range of commercial and recreational fisheries, fundamental information pertaining to diversity, distribution, and abundance estimates of sharks and rays is crucial for the development of effective management and conservation initiatives[7,8]
We report on the results from the first baited remote underwater video system (BRUVS) to be deployed in the Arabian Gulf waters of the United Arab Emirates (UAE) with the aim to (1) assess the relative abundance of sharks and rays across UAE Gulf waters using fishery-independent methods; (2) collect data on shark and ray distribution patterns and habitat associations; and (3) investigate how factors such as season, depth, habitat, and geographic stratum can influence the presence of sharks and rays
A total of 283 BRUVS were deployed during this period
Summary
Beyond the range of commercial and recreational fisheries, fundamental information pertaining to diversity, distribution, and abundance estimates of sharks and rays is crucial for the development of effective management and conservation initiatives[7,8]. The baited remote underwater video system (BRUVS) technique is established as a cost-effective, non-extractive means of providing a standardized, non-invasive, non-extractive, and non-destructive fishery-independent sampling method to (1) estimate the relative abundance of elasmobranchs across geographically wide areas as well as a range of habitats and depths that might otherwise be inaccessible; (2) provide estimates of species richness; (3) analyse species-specific behaviours; and (4) determine size and biomass when using stereo-cameras[4,5,8,11,12,13,14,15,16] This method uses bait to attract individuals into the field of view of a camera so that species can be identified and individuals counted. We report on the results from the first BRUVS to be deployed in the Arabian Gulf waters of the United Arab Emirates (UAE) with the aim to (1) assess the relative abundance of sharks and rays across UAE Gulf waters using fishery-independent methods; (2) collect data on shark and ray distribution patterns and habitat associations; and (3) investigate how factors such as season, depth, habitat, and geographic stratum can influence the presence of sharks and rays
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