The need for pelagic monitoring programmes is becoming increasingly urgent as the diversity and abundance of pelagic species decline and the pressure to meet global conservation targets rises (Letessier et al. 2017). While pelagic baited video techniques remain in their infancy, they show promise as efficient and affordable tools for monitoring wildlife communities and characterising biodiversity patterns at a range of spatial and temporal scales. For instance, Letessier et al. (2013b) and Heagney et al. (2007) were able to detect regional differences in the structure of pelagic fish assemblages, whilst Santana-Garcon et al. (2014b) reported changes in species diversity with water depth. Pelagic BRUVs may therefore be useful for providing rapid assessments of the effects of spatial closures, particularly as they are equally as efficient as benthic BRUVS in reducing overall costs and sampling footprint (Clarke et al. 2019). Although neither Heagney et al. (2007) nor Santana-Garcon et al. (2014c) found significant differences in species composition and relative abundance between fished and protected areas within their respective study sites, their data represent valuable baselines for future surveys. Knowledge of pelagic species distributions and habitat preferences are also critical to successful management, and pelagic BRUVs can yield geo-referenced data with sufficient replication to support the development of predictive statistical models (Bouchet & Meeuwig 2015). Lastly, pelagic BRUVs allow cost-effective observations of behaviour in free-ranging animals that might otherwise be difficult to obtain outside laboratory settings (Santana-Garcon et al. 2014a, Kempster et al. 2016, Ryan et al. 2018). Many aspects of the behaviour and basic biological requirements of pelagic fishes remain largely unknown, and pelagic BRUVs can thus be a powerful way of filling these knowledge gaps, for example by documenting biologically important areas like spawning (Fukuba et al. 2015) and nursery grounds (A. Forrest, unpublished data).
In brief, BRUV sampling (and by extension pelagic BRUV sampling) generates quantitative, monitoring-relevant data on:
- The extent and magnitude of anthropogenic impacts (e.g. fishing, climate change, oil and gas exploration, novel ecosystems such as man-made structures).
- Temporal and spatial variability in the relative diversity, abundance, and size structure of fish assemblages (when used in stereo).
- Behaviour observed in situ.
- Species-habitat relationships.
For a detailed overview of observational methods used in the spatial monitoring of fishes, with notes on baited videography, see Murphy & Jenkins (2010) and Mallet & Pelletier (2014). Struthers et al. (2015) offer additional insights into the value and limitations of action camera technology for field studies and education/outreach.