Nondestructive Monitoring of Soft Bottom Fish and Habitats Using a Standardized, Remote and Unbaited 360° Video Sampling Method

Abstract

Lagoon soft-bottoms are key habitats within coral reef seascapes. Coral reef fish use these habitats as nurseries, feeding grounds and transit areas. At present, most soft-bottom sampling methods are destructive (trawling, longlining, hook and line). We developed a remote, unbaited 360° video sampling method (RUV360) to monitor fish species assemblages in soft bottoms. A low-cost, high-definition camera enclosed in a waterproof housing and fixed on a tripod was set on the sea floor in New Caledonia from a boat. Then, 534 videos were recorded to assess the efficiency of the RUV360. The technique was successful in sampling bare soft-bottoms, seagrass beds, macroalgae meadows and mixed soft-bottoms. It is easy to use and particularly efficient, i.e., 88% of the stations were sampled successfully. We observed 10,007 fish belonging to 172 species, including 45 species targeted by fishermen in New Caledonia, as well as many key species. The results are consistent with the known characteristics of the lagoon soft bottom fish assemblages of New Caledonia. We provide future users with general recommendations and reference plots to estimate the proportion of the theoretical total species richness sampled, according to the number of stations or the duration of the footage.

Identifying fit-for purpose methods for monitoring fish communities

“…However, to our knowledge no studies focusing on fish using V-RUV have been conducted. Some studies also focus on a 360°view, which can be achieved either by using multiple cameras in an array, 360°cameras or rotating systems (Wells et al, 2008;Aguzzi et al, 2011;Pelletier et al, 2012;Schobernd et al, 2014;Starr et al, 2016;Mallet et al, 2021;Pelletier et al, 2021a;Pelletier et al, 2021b). Many of these techniques can be used not only with a single camera but also with a stereo camera, allowing more accurate length and field of view calculations (Harvey et al, 2002).…”

“…H-RUV (Fedra and Machan, 1979;Jan et al, 2007) RUV Rotating (Aguzzi et al, 2011;Pelletier et al, 2012;Pelletier et al, 2021a;Pelletier et al, 2021b) RUV 360° (Mallet et al, 2021) BRUV H-BRUV (Ellis and DeMartini, 1995) BRUV V-BRUV (Priede and Merrett, 1996; BRUV 360° (Wells et al, 2008;Schobernd et al, 2014) BRUV Stereo (e.g. Harvey et al, 2012;Langlois et al, 2015;Letessier et al, 2015) BRUV Rotating stereo (Starr et al, 2016) Hammerl et al 10.3389/fmars.2023.1322367 extracted from the filter, sequenced, detected and then analyzed (see Garlapati et al, 2019).…”

Functional and Taxonomic Overlap in Shore Fish Assemblages in a Tropical Seascape

“…Surveys on soft-bottoms are usually conducted either with a shrimp trawl or a fish trawl, both being seldom combined as in the present study. The addition of visual or video surveys has been rarely performed on soft-bottoms, but see recent work with stationary video cameras by Malet et al [51] or the review on the uses of videos to assess fish assemblages by Harvey et al [52]. As a result, very few studies in the Indo-Pacific regions reach such species diversities.…”