DEMOGRAPHIC-STUDIES OF ANTARCTIC KRILL EUPHAUSIA-SUPERBA IN THE COOPERATION AND COSMONAUT SEAS (INDIAN SECTOR OF THE SOUTHERN-OCEAN)

The reproductive state and size composition of Euphausia superba Dana collected in the Indian sector of the Southern Ocean from 1985 to 1990 were analyzed to estimate its growth, life span and mortality rates. The life span of E. superba exceeded 5 yr in the Cosmonaut Sea and 6 yr in the Cooperation Sea. Assuming growth for only 180 d per year, growth rates ranged from 0.120-0.133 mm d(-1) during the first year of life to 0.019-0.022 mm d(-1) during the fifth year. Von Bertalanify growth curves calculated for different areas are similar to those obtained by Australian researchers in the Prydz Bay region for 1981 to 1985, in mid summer, E. superba of age 2+ to 4+ were predominant in all hauls made south of the Antarctic Divergence, while north of the Divergence the krill were clearly dominated by individuals of age 4+. The coefficients of natural mortality (M) of E. superba in the Indian sector of the Southern Ocean, calculated by the methods of Alverson & Carney, Richter and Efanov and Beverton and Holt, varied from 0.72 to 0.87, from 0.52 to 0.57 and from 0.76 to 2.92, respectively. The value of age-dependent natural mortality of E. superba derived using Zikov and Slepokurov's method ranged from 0.52 during the maturation period to 1.1-2.41 during the first and last years of life. Based on long-term observations, the relationship between E. superba age composition and its spawning success is examined for the coastal areas of the Cooperation and Cosmonaut Seas.