Lowered cameras reveal hidden behaviors of Antarctic krill.

Antarctic krill (Euphausia superba, hereafter 'krill') exemplify the methodological challenges of studying small, mobile, aggregating pelagic organisms. Krill are a central species in the Southern Ocean food web, provide important biogeochemical functions and support a valuable commercial fishery. Most of what we know about krill has been derived from acoustic surveys and net samples, the former being essential for estimating krill biomass and catch limits. However, understanding krill behavior, particularly in the poorly-studied autumn-winter seasons, is key for management and conservation. Here, we used seasonal video observations collected with a profiling camera system of krill along the Western Antarctic Peninsula to reveal krill vertical distribution, aggregation density and individual behaviors that have remained hidden from traditional sampling methods..