Abstract:

During the First Chinese Antarctic Expedition, in water northeast of King George Island krill (Euphausia superba Dana) swarms were found and observed by echosounder (200 kHz) , and 15 IKMT (Isaacs-Kidd midwater trawl) tows were made in an area of 3 x 5 nautical mile. The population structure of 6 samples were analysed by means of L-F distribution and sexual maturity stage composition. The percent similarity indices of L-F distribution between samples are very high, 84.3% in average. That of sexual maturity stage composition is 75.6% in average. The population structures inside the searched area are quite similar. Echograms show that the swarms are distributed mainly in a layer at 20-50 m depth. Its upper limit is quite stable, but the lower limit varies greatly according to the thickness of the swarm. The highest density observed is 4418 individuals/ 1000 cubic meter, . only 1400 individuals / 1000 cubic meter in average, and much lower than that of swarms commercially harvested. The temperature of water in which swarms occurred ranges from 0.85 to 1.65℃, and the salinity 34.003-34.163‰. Adults constitute the great majority (96.5%) of the population. Among females, gravid female accounts for 33.6%, spent female 2.3% .Judging from the sexual maturity stage composition, the maximum spawning for the swarms in this area would occur in late February.