Size and stage composition of age class 0 Antarctic krill (Euphausia superba) in the ice-water interface layer during winter/early spring

摘要

The condition and survival of Antarctic krill (Euphausia superba) strongly depends on\udsea ice conditions during winter. How krill utilize sea ice depends on several factors\udsuch as region and developmental stage. A comprehensive understanding of sea ice\udhabitat use by krill, however, remains largely unknown. The aim of this study was to\udimprove the understanding of the krill's interaction with the sea ice habitat during\udwinter/early spring by conducting large-scale sampling of the ice-water interface (0-2\udm) and comparing the size and developmental stage composition of krill with the\udpelagic population (0-500 m). Results show that the population in the northern Weddell\udSea consisted mainly of krill that were less than one year old (age class 0; AC0), and\udthat it was comprised of multiple cohorts. Size per developmental stage differed\udspatially, indicating that the krill likely were advected from various origins. The size\uddistribution of krill differed between the two depth strata sampled. Larval stages with a\udrelatively small size (mean 7 to 8 mm) dominated the upper two meter layer of the\udwater column, while larger larvae and AC0 juveniles (mean 14 to 15 mm) were\udproportionally more abundant in the 0-500 m stratum. Our results show that, as krill\udmature, their vertical distribution and utilization of the sea ice appears to change\udgradually. This could be the result of changes in physiology and/or behaviour, as e.g.\udthe krill's energy demand and swimming capacity increase with size and age. The\uddegree of sea ice association will have an effect on large-scale spatial distribution\udpatterns of AC0 krill and on predictions of the consequences of sea ice decline on their\udsurvival over winter.