Bait increases the precision in count data from remote underwater video for most subtidal reef fish in the warm-temperate Agulhas bioregion

Abstract

Baited remote underwater video (BRUV) has been identified in the literature as a powerful long-term monitoring tool for subtidal rocky reef fish communities. To test this, a repeated-measures field experiment comparing unbaited remote underwater video (RUV) with BRUV was conducted in the Tsitsikamma National Park Marine Protected Area between June 2008 and February 2010. The results demonstrate that BRUV was more efficient at surveying the entire fish community, specifically invertebrate carnivores, generalist carnivores and cartilaginous species. On the other hand, RUV was more effective at surveying microinvertebrate carnivores. High variability in the RUV data resulted in the method requiring a greater number of samples to achieve the same diagnostic power as BRUV. However, RUV required a shorter deployment and post-sampling video analysis time, making it more time efficient. Baited remote underwater video was more sensitive in the detection of differences in abundance between habitat types, while the RUV data were more prone to an intra-species methodological bias linked to the percentage of reef visible in the frame of view. The scale of the response to the presence of bait was inconsistent among species, indicating that behaviour determined the area surveyed within the bait plume of BRUV. The benefits gained by sampling the fish community with RUV do not outweigh those obtained by altering the community through the presence of bait. However, in combination, the 2 methods are highly effective at monitoring the subtidal fish communities in the Agulhas bioregion of South Africa. Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 471: [235][236][237][238][239][240][241][242][243][244][245][246][247][248][249][250][251][252] 2012 trawls , Cappo et al. 2004, Watson et al. 2005, Colton & Swearer 2010, Pelletier et al. 2011. The core strengths lie in the method's ability to survey components of the fish community typically missed by UVC techniques, such as large piscivorous fish , Cappo et al. 2004, Brooks et al. 2011, the higher diagnostic power achieved through reduced variability in the data (Watson et al. 2005, Stobart et al. 2007) and the ability to provide accurate measures of fish length when set up with stereo-cameras (Harvey & Shortis 1996, Harvey et al. 2004, Watson et al. 2009). Data collected with BRUV are not biased by the presence of an observer in the water that can alter the behaviour of the fish, and observer bias during analysis is kept to a minimum, as the video is available for reanalysis if erroneous data are de tec ted (Cappo et al. 2003(Cappo et al. , 2007b. Furthermore, BRUV is a non-destructive and non-extractive sampling tool and is thus ideally suited to monitor protected fish populations inside marine reserves , Cappo et al. 2007b.As with all survey methods, BRUV is characterised by a number of shortcomings. For example, past studies indicate that BRUV is unable to survey herbivorous fish as efficiently as UVC (Colton & Swearer ...

Distinct cross-shelf gradient in mesophotic reef fish assemblages in subtropical eastern Australia

“…1). The BRUV method has known biases in that it attracts predatory and scavenging species and under-represents herbivores (see Colton & Swearer 2010 for example); nevertheless, it is acknowledged as one of the most precise methods available for fish abundance surveys (Bernard & Götz 2012) since it is not affected by diver avoidance or errors associated with various capture techniques. Moreover, it is lowimpact and useable at any depth, on any substrate.…”

Mesophotic Depth Gradients Impact Reef Fish Assemblage Composition and Functional Group Partitioning in the Main Hawaiian Islands

“…Each BRUVS was deployed for a 60 min sampling period (Watson et al, 2005;Bernard and Götz, 2012), using ∼800 g of Pacific saury/Japanese sanma (Cololabis saira) pulped into a wire mesh basket 1.2 m in front of the stereo-cameras. We selected C. saira because it is locally available and functionally similar to the more commonly used pilchard (Sardinops sagax), as both are oily soft-fleshed fishes widely used by fishers as attractants.…”

“…Fish species sampled by BRUVS in the MHI were assigned to functional group categories, as described in Harvey et al (2007) and Bernard and Götz (2012), based on dietary, behavioral, and morphological traits. The NOAA PIFSC CREP MHI reef fish database (Heenan et al, 2014), and FishBase, ver.…”

An exploratory investigation of the fish communities associated with reefs on the central Agulhas Bank, South Africa

“…Furthermore, both methods have to be used in combination if the survey needs to be representative of the fish community, thereby increasing the sampling effort and adding logistical challenges. The recent development of remote video survey techniques in South Africa such as baited remote underwater video systems (BRUVs) and stereo-BRUVs (Bernard & Götz 2012;Bernard et al, in press) has the potential to further improve the quantitative aspects of scientific fish survey methodology while avoiding the negative impacts of extractive survey methods (Bernard 2012).…”