Cost-efficient sampling of fish assemblages: comparison of baited video stations and diver video transects

Abstract

Baited remote underwater stereo-video (stereo-BRUV) stations and diver operated stereo-video (stereo-DOV) transects are increasingly used to sample both tropical and temperate fish assemblages. Compared to in situ visual census methods, the use of stereo-video reduces interobserver variability, improves definition of the sample unit area, increases accuracy of fish length estimates and provides a permanent record of the assemblage that can be validated where required or independently reanalysed. Previous studies have suggested that stereo-BRUV collects representative data on both carnivorous and herbivorous species and can be more cost-efficient than diverbased survey methods. This study compares estimates of common fish assemblage metrics obtained with stereo-BRUV stations and stereo-DOV transects across 3 biogeographic regions, and uses a costoptimization procedure to compare the efficiency of these 2 methods. Stereo-BRUV stations were found to sample greater species richness and obtain greater estimates of relative biomass of generalist carnivores, but no differences occurred in the biomass of herbivores sampled by the 2 techniques. Stereo-BRUV stations generally obtained estimates of assemblage metrics with less variance, resulting in greater power to detect spatial and temporal changes in the fish assemblage metrics. Cost -benefit analyses found that stereo-BRUV was generally more time efficient than stereo-DOV transects in terms of smaller standard error around the mean of the various metrics considered. However, across the 3 biogeographic regions sampled there was considerable variation in the magnitude of these differences. Results suggest that stereo-BRUV stations are, in general, a more cost-effective method for monitoring fish assemblages than stereo-DOV transects.KEY WORDS: Cost -benefit · Power to detect change · Biogeography · Baited remote underwater stereo-video · Diver operated stereo-videoResale or republication not permitted without written consent of the publisher Biol 9: 155-168, 2010 replicates and sites from pilot study data and, therefore, can also be used to evaluate the cost-effectiveness of different sampling methods.The complete sampling of reef fish communities in shallow waters is only possible using destructive methods. Indiscriminate methods such as dynamite have historically been used (Stephan 1904); however; the use of fish toxins such as rotenone (Krumholz 1948) have allowed more discrete and quantitative samples of the fish assemblage to be collected from complex habitats (Robertson & Smith-Vaniz 2008). Recent advances in diving technology have allowed these methods to be used to depths of 150 m, resulting in the description of large numbers of new cryptic species and observations of higher rates of endemism in deeper compared to shallow reefs (Pyle 2000). However, for most largescale studies, sampling the complete fish assemblage is likely unnecessary (Clarke & Warwick 1998) and destructive methods bias future samples obtained from the same locality and can compr...

Marinas as habitats for nearshore fish assemblages: comparative analysis of underwater visual census, baited cameras and fish traps

“…BCs depend on the species-specific movement of individuals within the field of view. This method has proved to be effective at recording highly piscivorous species, which usually avoid divers; it has also been shown to record herbivorous and omnivorous species (Cappo et al 2006, Langlois et al 2010. We also found that UVCs recorded a greater number of cryptic species, while BCs recorded more piscivorous species.…”

“…Greater efficiencies of UVCs and BCs are not surprising, especially in sampling complex habitat types such as artificial structures. UVCs allow a diverse set of habitats to be sampled, and they are therefore more likely to encounter both pelagic and benthic species (Langlois et al 2010, Stobart et al 2007, Colton and Swearer 2010. Furthermore, their active nature favours the encounter of cryptic species, which are usually hidden under crevices or in holes (Colton andSwearer 2010, Lowry et al 2012).…”

“…relative abundances, size and habitat characteristics) (Harmelin-Vivien et al 1985). However, they involve certain sources of bias, such as species-specific adaptations to diver presence, in situ species misidentification and inter-observer variability in abundance and size estimates (Edgar et al 2004), which in turn can affect the suitability of the data and compromise our ability to detect significant changes in an ecological study (Langlois et al 2010, Wakefield et al 2013. Though this is widely acknowledged, most studies focusing on fish assemblages associated with artificial structures have exclusively relied on UVC techniques.…”

“…Filming times of between 25 and 30 min were indicated to obtain accurate relative abundances of fish species (Stobart et al 2007, Langlois et al 2010. At Gran Canaria, once the BCs had been recovered, the same procedure was repeated on the same side but at different places (n=6), to reach a total of 60 deployments and 27 h of video recording for the whole study.…”

Estimating relative abundance and species richness from video surveys of reef fishes

“…Although numerous underwater video approaches and techniques have been used to index abundance, many researchers now employ some version of a stationary point-count method with baited remote underwater video stations (BRUVS) Cappo et al, 2004). BRU-VS sampling has many advantages: 1) it is nonextractive and, therefore, preferred in no-take areas, 2) is less size-or species-selective than other baited gears, 3) can sample deeper waters more easily than diver surveys and do so at lower costs than can autonomous underwater vehicles, 4) provides a permanent record available to be reviewed for accuracy by multiple readers, and 5) can capture habitat characteristics of a survey site and behavioral interactions among species (Silveira et al, 2003;Wells et al, 2008;Langlois et al, 2010;Bacheler et al, 2013).…”