Cameras and carcasses: historical and current methods for using artificial food falls to study deep-water animals

Deep-ocean animals remain poorly understood compared to their shallow-water relatives, mainly because of the great cost and difficulty involved in obtaining reliable ecological data. This is a serious issue, as exploitation of deep-water resources progresses without sufficient data being available to assess its risks and impacts. First described almost 40 yr ago, the use of baited cameras was pioneered by deep-sea biologists and is now a widely used technique for assessing patterns of animal behavior, abundance, and biodiversity. The technique provides a non-destructive and cost-effective means of collecting data, where other techniques such as trawling are difficult or impractical. This review describes the evolution of baited camera techniques in deep-sea research from the early deployments, through recent programs to investigate trends in animal distribution with depth, latitude, and ocean basin. The techniques used for imaging, baiting, and analysis are synthesized, with special consideration of the modeling techniques used in assessing animal abundance and biomass.