In-situ (video) observations on the distribution and behavior of amphipods and Arctic cod (Boreogadus saida) under the sea ice of the High Arctic Canada Basin, August 2002

The occurrence and behavior of sympagic amphipods and Arctic cod (Boreogadus saida) were studied in the High Arctic Canada Basin by diving under the ice at seven stations in summer 2002. The data set consists of 12 rows and two species. Still images of video-transects were used to obtain animal abundances and information on the structure of the ice environment. Mean amphipod abundances for the stations varied between 1 and 23 individuals m–2, with an increase towards the western part of the basin. The standard deviation within the 31–51 images analyzed per station was small (<1 individual m–2). Gammarus wilkitzkii was found in low abundances, often hiding in small ice gaps. Small amphipods (Onisimus spp., Apherusa glacialis, and juveniles of all species) tended to move freely along the bottom of the floes. B. saida occurred in narrow wedges of seawater along the edges of melting ice floes at three stations in water depths of 10–50 cm and was never found under the ice. The fish occurred in schools of 1–28 per wedge. Fish were inactive and did not escape the approaching diver. Resting in the wedges may be a strategy to reduce energetic requirements and avoid predators.