ZOOPLANKTON BIOMASS AND ABUNDANCE OF ANTARCTIC KRILL EUPHAUSIA-SUPERBA DANA IN INDIAN-OCEAN SECTOR OF THE SOUTHERN-OCEAN

Zooplankton sampling was carried out during the first six Indian Scientific Expeditions to Antarctica (1981-1987) to estimate krill abundance in the Indian sector of the southern ocean (between 35-degrees to 70-degrees-S and 10-degrees to 52-degrees-E). This study aims to understand the distribution of biomass of zooplankton, especially the krill, using the data collected by net sampling techniques. Total zooplankton biomass for all the sampling stations ranged from 9 to 684 ml/1000 m3 (xBAR: 143.34 +/- 138.61 SD; n = 150). Biomass data grouped by 5-degrees latitude interval shows the presence of higher biomass (xBAR: 191 ml/1000 m3; n=31) in the Antarctic divergence region (between 60-degrees to 65-degrees-S). Euphausiid Euphausia superba DANA formed a considerable component of biomass and together with eggs and larvae represented over 60% (n = 39) of mean total zooplankton-biomass in the coastal ice region. The values for population density and biomass of adult-size krill varied between 0 to 4320 individuals and 6 to 305 ml/1000 m3, respectively. The highest values were recorded between 62-degrees to 69-degrees-S and between 16-degrees to 30-degrees-E. A high density of krill larvae was encountered in the shelf region during January 1987 which was related to chlorophyll concentration. However, the values obtained during six consecutive summers showed that values of adult krill biomass at given location was highly variable and, hence, not comparable on inter-annual basis, during the sampling years.