A low-cost, long-running, open-source stereo camera for tracking aquatic species and their behaviours

Ecologists are now widely utilising video data to quantify the behaviours and interactions of animals in the wild. This process can be facilitated by collecting videos in stereo, which can provide information about animals' positions, movements and behaviours in three-dimensions (3D). However, there are no published designs that can collect underwater 3D stereo data at high spatial and temporal resolutions for extended periods (days). Here, we present complete hardware and software solutions for a long-running, open-source, underwater stereo camera rig, costing 1337 pound. This stereo camera can continuously record aquatic species and their behaviours/interactions in high resolution (1080 p and 30 fps) and in 3D, over multiple days. We provide full design guides for the cameras and a travel-friendly rig, and include guidance and open-source code for calibrating the cameras in space and time. We also show how these cameras could be used to track animals' body parts and positions, and how their size, posture and behaviour can be inferred. This stereo camera will facilitate the collection of high-resolution ecological and behavioural data, such as affiliative, agonistic or trophic interactions between species, which can inform us about the health and structure of ecosystems. These data will assist ecologists and conservationists in monitoring and understanding the impacts of current environmental pressures on ecosystem functioning.