Assessing Caribbean Shallow and Mesophotic Reef Fish Communities Using Baited-Remote Underwater Video (BRUV) and Diver-Operated Video (DOV) Survey Techniques

Abstract

Fish surveys form the backbone of reef monitoring and management initiatives throughout the tropics, and understanding patterns in biases between techniques is crucial if outputs are to address key objectives optimally. Often biases are not consistent across natural environmental gradients such as depth, leading to uncertainty in interpretation of results. Recently there has been much interest in mesophotic reefs (reefs from 30–150 m depth) as refuge habitats from fishing pressure, leading to many comparisons of reef fish communities over depth gradients. Here we compare fish communities using stereo-video footage recorded via baited remote underwater video (BRUV) and diver-operated video (DOV) systems on shallow and mesophotic reefs in the Mesoamerican Barrier Reef, Caribbean. We show inconsistent responses across families, species and trophic groups between methods across the depth gradient. Fish species and family richness were higher using BRUV at both depth ranges, suggesting that BRUV is more appropriate for recording all components of the fish community. Fish length distributions were not different between methods on shallow reefs, yet BRUV recorded more small fish on mesophotic reefs. However, DOV consistently recorded greater relative fish community biomass of herbivores, suggesting that studies focusing on herbivores should consider using DOV. Our results highlight the importance of considering what component of reef fish community researchers and managers are most interested in surveying when deciding which survey technique to use across natural gradients such as depth.

A Multidisciplinary Approach for Generating Globally Consistent Data on Mesophotic, Deep-Pelagic, and Bathyal Biological Communities

“…Divers can operate equipment close to the seabed, overcoming the challenges of sampling steep slopes associated with some survey techniques. Among other uses, stereo-video can assess fish biomass with the added benefit of allowing short survey times, while gaining accurate length estimates of individual fishes (Harvey et al, 2001;Andradi-Brown et al, 2016b). Divers can now also carry many other instruments normally deployed by deep-sea landers (e.g., temperature loggers, sediment corers, sediment traps), particularly with increasing miniaturization of sensors; they can also sample organisms directly.…”

Comparative cleaning behaviour of Pederson's cleaner shrimp (Ancylomenes pedersoni) between geographically close yet ecologically dissimilar coral reef habitats

“…Filming for DOV was generally from a distance of 0.5 m off the substratum. Transects took ~3 minutes to complete, which was a duration deemed fast enough to minimize risk of double-counting individuals (Andradi-Brown et al ., 2016 a ). Fish surveys commenced promptly upon water entry with the camera operator leading the way in order to minimize any potential effect of diver presence on fish behaviour.…”

“…A diver-operated stereo-video (DOV) was used that consisted of two Cannon HFS21 cameras at fixed angles filming the same position. Six replicate 50 m transects were surveyed at 5 and 15 m depth each on Utila and 10 and 15 m each on Banco Capiro, following transect methods detailed by Andradi-Brown et al (2016a). These depths were selected to represent the fish assemblages at both the crest and the slope of the reefs, encompassing the depth range in which cleaner stations were monitored.…”

A Time-Extended (24 h) Baited Remote Underwater Video (BRUV) for Monitoring Pelagic and Nocturnal Marine Species

“…Despite relatively high device cost and labor-intensive video data analysis [3], BRUVs have been widely used in studies characterising species diversity and abundance of fishes (see review by [4]). The diversity of BRUV studies includes characterisation of mesophotic (30-150 m depth) reef fish communities [5], monitoring of the fish fauna associated with seagrass habitats [6], assessment of behavioural responses to playback noise [7], and the attractiveness of animal vs plant-based baits to reef fishes [8]. The strong attractiveness of bait to sharks [9], has also made BRUVs efficient tools for assessing shark populations.…”