Optimal soak times for Baited Remote Underwater Video Station surveys of reef-associated elasmobranchs

Currey-Randall, Leanne M., Cappo, Mike, Simpfendorfer, Colin A., Farabaugh, Naomi F., and Heupel, Michelle R. (2020) Optimal soak times for Baited Remote Underwater Video Station surveys of reef-associated elasmobranchs. PLoS One, 15 (5). e0231688.

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Effective sampling of marine communities is essential to provide robust estimates of species richness and abundance. Baited Remote Underwater Video Stations (BRUVS) are a useful tool in assessment of fish assemblages, but research on the optimal sampling period required to record common and rare elasmobranch species is limited. An appropriate 'soak time' (time elapsed between settlement of the BRUVS on the seabed and when it is hauled off the seabed) requires consideration, since longer soak times may be required to record species rare in occurrence, or sightings in areas of generally low elasmobranch abundance. We analysed 5352 BRUVS deployments with a range of soak times across 21 countries in the Coral Triangle and Pacific Ocean, to determine the optimal soak time required for sampling reef-associated elasmobranchs, considering species rarity, and community abundance at each site. Species were categorised into 4 'rarity' groups (very rare to common), by their relative occurrence in the dataset, defined simply by the proportion of BRUVS on which they occurred. Individual BRUVS were categorised into 3 'abundance' groups (low to high) by overall relative elasmobranch abundance, defined as total number of all elasmobranchs sighted per unit of sampling effort. The effects of BRUVS soak times, and levels of rarity and abundance groupings, on the time to first sighting (TFS) and time to maximum number of elasmobranchs observed (t(MaxN)) were examined. We found that TFS occurred earlier for species groups with high occurrence, and on BRUVS with high elasmobranch abundance, yet longer soak times were not essential to observe rarer species. Our models indicated an optimum of 95% of both sighting event types (TFS, t(MaxN)) was recorded within 63-77 minutes, and a soak time of 60 minutes recorded 78-94% of the elasmobranch sighting events recorded (78-94% of TFS events and 82-90% of t(MaxN) events), when species rarity and abundance on BRUVS was accounted for. Our study shows that deployments of similar to 77 minutes are optimal for recording all species we observed, although 60 minutes soak time effectively samples the majority of elasmobranch species in shallow coral reef habitats using BRUVS.

Item ID: 63574
Item Type: Article (Research - C1)
ISSN: 1932-6203
Copyright Information: © 2020 Currey-Randall et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and sourceare credited.
Funders: Paul G. Allen Philanthropies (PGAP), Pew Foundation, Florida International University's Tropial Conservation Institute
Projects and Grants: PGAP 11861
Date Deposited: 24 Jun 2020 07:33
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 40%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 30%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300502 Aquaculture and fisheries stock assessment @ 30%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 80%
83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830204 Wild Caught Fin Fish (excl. Tuna) @ 20%
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