Baited Remote Underwater Video

In recent years there has been an expansion in the application of baited remote underwater video stations (BRUVs) to survey marine and freshwater communities across a variety of habitat types. Their use has enabled scientists to overcome sampling limitations imposed by depth, behaviour, seafloor rugosity and the selectivity inherent in hook, trap and trawl methods. BRUVs are now proving particularly important for surveying numbers and lengths of animals in marine parks where non-destructive sampling is essential, and for animals of special conservation significance, such as sharks. In general terms, a bait plume is used to attract vertebrates and invertebrates into the field of view of a video camera where they are identified, counted and often measured.

BRUVs were first established at BBFS in 2013. Currently the technique is being used to examine the distribution and abundance of sharks, rays, and their prey and predators. In brief BRUVs frames are constructed using stainless steel rods welded to create a pyramid. A stainless steel bait arm extends out from the centre of the frame with a wire box containing chum (1kg) within a mesh bag. A camera (GoPro) is set facing the bait box just above the bait arm. On deployment BRUV frames are positioned with the camera facing downstream of the current, thus maximizing observation of fish approaching the bait arm via the bait plume.  
 
At the Sharklab BRUVs are deployed over different seasons, tidal phases and habitats including seagrass beds, sand flats and mangrove fringes. GoPro’s are set to record for 70 min including a 10 min buffer for disturbance. At the start and end of deployments we also record environmental conditions such as water depth, temperature, salinity, flow velocity and direction as well as seagrass cover, visibility and wind speed in order to determine their influence on the species recorded. Analysis involves two observers watching the 60 min video playback in ‘real time’. They record the initial time of appearance, as well as the maximum number of individuals in a single frame for each species. In some circumstances individuals of the same species can be identified according to size, sex and definitive markings. 

So far we have recorded 19 families of teleosts, 1 species of marine reptile (loggerhead turtle), 4 species of invertebrates, and 4 species of elasmobranchs (Great Hammerhead shark, Bull shark, Nurse shark, and Caribbean reef shark)!

Bond et al. 2012. Reef Sharks Exhibit Site-Fidelity and Higher Relative Abundance in Marine Reserves on the Mesoamerican Barrier Reef. PloS One. 7(3): e32983. doi:10.1371/journal.pone.0032983
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