Population structure and condition of Antarctic krill (Euphausia superba) off East Antarctica (80–150°E) during the Austral summer of 1995/1996

This paper summarises the results of krill demographic studies from BROKE—a large-scale survey off East Antarctica conducted in January – March, 1996. The survey progressed from 80°E in late January to 150°E in mid March. Krill varied in mean size across the survey area, and the various maturity stages showed some longitudinal and latitudinal trends. Males, early stage females, and juveniles were, on average, larger in the east of the survey area whereas gravid and spent females differed little in length across the survey area. Gravid females were only found north of the shelf break; juveniles, males and other stages of females were found throughout the latitudinal extent of the survey. Growth rate measurements resulted in comparable figures to other studies in the Indian Ocean and were greatest in February for all stages. Observed growth rates were sufficient to account for the changes in mean sizes of krill observed across the survey area. The mean density of krill revealed by nets (2.65 krill per 1000 m−3) was low compared to other areas that have been surveyed. Similarly, the overall estimates of proportional recruitment were below average when compared to the range of reported values. Krill larvae were moderately abundant in the survey area but were more frequently encountered in the east, which is probably a function of the lateness of the season when the larvae would be rising into the surface layer sampled by the net.