Geographical distribution and age composition of Euphausia superba larvae (Crustacea: Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions

Abstract

Spatial distribution patterns of the different life stages of Euphausia superba in the region of the South Shetland Islands and southern Scotia Sea (Antarctica) were assessed based on scientific survey data collected in January and February of 2010. Adults, eggs, nauplii, metanauplii, calyptopis I-III, and furcilia I-II were found in the investigation. The abundance of larvae averaged 1 172.8 ind./m2, with calyptopis I and II as the dominant stages. Habitat occupancy patterns varied among Euphausia superba at different stages, and three sub-regionswere identified by cluster analysis. The degree of larval development increased fromwest to east. Larvae were not observed north of the South Shetland Islands. Calyptopis I was predominant in the water between Elephant Island and the South Orkney Islands, which featured no thermocline. Older stages, including calyptopis II and III and furcilia I and II, were common in north and northeast of the South Orkney Islands, which were characterized by high temperature and high chlorophyll concentration. Distribution and abundance of the early life stages of E. superba were associated with specific environmental conditions. According to Biota-Environment matching (BIOENV), the distributions of E. superba larvae were correlated with a combination of temperature at the surface and 200m, and 0–100 mintegrated chlorophyll a concentration.