Are we underestimating elasmobranch abundances on baited remote underwater video systems (BRUVS) using traditional metrics?

Sherman, C. Samantha, Chin, Andrew, Heupel, Michelle R., and Simpfendorfer, Colin A. (2018) Are we underestimating elasmobranch abundances on baited remote underwater video systems (BRUVS) using traditional metrics? Journal of Experimental Marine Biology and Ecology, 503. pp. 80-85.

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Baited remote underwater video systems (BRUVS) are increasingly used to study fish communities, biomass, and animal behaviour. Due to the abundance of BRUVS data, there are many analysis methods. The most commonly used method for analysis of BRUV data is MaxN which refers to the maximum number of individuals observed of a species in a single frame of a video. Here, we present a novel method for BRUVS analysis that involves identifying and counting distinct individuals (MaxIND) to quantify the accuracy of MaxN. Individual oriental bluespotted maskray (Neotrygon orientalis) and the bluespotted fantail ray (Taeniura lymma) were identified on BRUVS by spot patterns, tail characteristics, and sex at three sites in Malaysian Borneo. We demonstrated that MaxIND gave abundances that were 2.4 and 1.1 times higher than MaxN for N. orientalis and T. lymma, respectively. These differences between methods were consistent for each species between sites regardless of the presence of marine reserves. However, differences in abundance estimates from MaxN to MaxIND were apparent between species, indicating that correction factors need to be developed on a species basis to better estimate true abundance. While identifying individuals is time consuming, it provides improved accuracy and information about populations. We therefore recommend the use of MaxIND when rare and endangered species are present, in high density populations, and for behavioural analyses.

Item ID: 57460
Item Type: Article (Research - C1)
ISSN: 0022-0981
Keywords: BRUVS; batoids; analysis methods; individual identification; coral reefs; marine reserves
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Copyright Information: Copyright © 2018 Elsevier B.V. All rights reserved.
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A version of this publication was included as Chapter 3 of the following PhD thesis: <Sherman, Carolyn Samantha (2019) Ecology of rays on tropical coral reefs. PhD thesis, James Cook University.>, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Paul G. Allen Philanthropies (PGAP)
Projects and Grants: PGAP Global FinPrint Project
Date Deposited: 14 Mar 2019 04:17
FoR Codes: 31 BIOLOGICAL SCIENCES > 3109 Zoology > 310901 Animal behaviour @ 30%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 70%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 70%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 30%
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