Krill biomass and distribution in Subarea 48.2 during summer 1996

The results of hydroacoustic survey of krill biomass assessment in Subarea 48.2 adjacent to Coronation Island, carried out in February-March 1996 in Russian RN "ATLANTNIRO" are presented. Taking in account close relation of krill and oceanographic structure of waters and currents, hydrorological conditions during surveys are also discussed in the paper. Average weighed density of krill in the study area amounted to 17 g/sq.m, obtained on the basis of diurnal surveys, and average weighted krill density in the day-time amounted to 30.4 g/sq.m are comparable with density values, observed in the process of interannual krill density variability in other areas of Scotia Sea. However, density values obtained seem to be considered as underestimated and typical only for the late summer season, since in the early summer season krill density may be higher. Krill biomass estimate (1.12 ± 0.093 mln.t) in acoustic survey area, obtained in the basis of average weighted density in the day-time and night hauls, is characterized by relatively high accurancy (CV = 4.1 %). However, this estimate is likely to be biased towards underestimation which is explained by systematic error caused by krill abundance underestimation during night hauls. We consider, that krill biomass, estimated on the basis of average weighed krill density in the day-time (30.4 g/sq.m) provides a more accurate value of krill abundance in the study area. This biomass amounted to 2.00 ± 0.573 mln.t with a coefficient of variance 12.5%.