Comparison of video and diver observations of sharks from a fishery-independent trap-video survey off east-central Florida, including utility of an alternative method of video analysis

Abstract

The views and opinions expressed or implied in this article are those of the author (or authors) and do not necessarily reflect the position of the National Marine Fisheries Service, NOAA. Abstract—We assessed the utility of an alternative method of video analysis for generating data for sharks and compared observations of sharks from the use of baited remote underwater video stations (BRUVS) with observations made by scuba divers during surveys conducted simultaneously with BRUVS video recordings. Videos were made off east-central Florida as part of a fishery-independent trap-video survey of fish species in hard-bottom reef habitats. In videos from 25 of 72 sites, we observed sharks, including the nurse (Ginglymostoma cirratum), tiger (Galeocerdo cuvier), spinner (Carcharhinus brevipinna), sandbar (C. plumbeus), Atlantic sharpnose (Rhizoprionodon terraenovae), bull (C. leucas), and lemon (Negaprion brevirostris) sharks. In contrast, divers observed 3 species of sharks at 5 sites. We conclude that video observations are superior to diver observations for detecting sharks. Rapidly viewing an entire video (the alternative method), rather than viewing only a 20-min segment (the standard protocol), has the potential to increase the number of sites where sharks are observed and the number of shark species that are observed in video analysis (as it did, by 400% and 40%, respectively, in this study). This method holds promise for providing critical information without extraction of specimens and for aiding stock assessments and essential fish habitat delineation for these important predators. Predation is recognized as a key ecological and evolutionary process, and sharks, a group that includes species capable of being the top predators in oceans, are important members of marine communities (Estes et al., 2011; Osgood and Baum, 2015; Barley et al., 2017). Sharks are capable of exerting top-down effects on prey from lower trophic levels over wide spatial and temporal scales (Osgood and Baum, 2015; Barley et al., 2017; Dulvy et al., 2017), and shark species are valuable targets of recreational and commercial fisheries. To help protect species that have relatively low reproductive rates, late maturity, and slow growth, the United States has implemented shark management measures that are some of the strongest worldwide (NMFS1). Despite conservation efforts, global bycatch of sharks and demand for shark fins and meat have resulted in ~25% of shark species listed as endangered, vulnerable, or near threatened by the International Union for Con-