Abstract:

Based on the survey data carried out in the Prydz Bay region by the Southern Ocean Expedition of China during the austral summer of 1991/1992 and 1992/1993,this paper deals with the horizontal and vertical distribution and the estimation of the standing crops of Antarctic krill in the surveyed areas by using the integral system of relative quantitative assessment of the images recorded by echo sounders and the area method of the images recorded by trawling,respectively.The results are as follows: 1.The Antarctic krill were mainly distributed along the area of 63°-67°S,68°E during the period of investigation in summer of 1991/1992.The total area of the images of krill obtained from echo sounders in the five sub areas was 875134.42m 2,which accounted for 58.4% of the total area of the images.In 1992/1993,the main distributions of krill was along the areas of 63°￣66°S,68°E;65°￣67°S,73°E and 63°￣65°S,78°E,in which the total area of the images of krill aggregation was 276925.5m 2,or 61.15% of the total area of images of krill aggregation.The results of these two investigations and those of 1990/1991 showed that the denser area of krill aggregation was along the area of 63°￣67°S,68°E off the Prydz Bay.The reason for its aggregation has a relation to the existence of thermocline. 2.The investigation in 1991/1992 showed that the Antarctic krill aggregation was chiefly in the layers between 20m and 60m,with its image area representing 80.88% of the total image area.In 1992/1993 the survey indicated that the main distribution of Antarctic krill aggregation was in the layers between 10m and 50m,with its image area accounting for 87.18% of the total image area.The main krill aggregation occurred in the layer upper than 70m and had more regular pattern in vertical movements,that is,concentrating in the surface at night and surmerging to the deeper layer in the daytime. 3.The standing crops of Antarctic krill was 1.699×10 6 tons in the surveyed waters of 150533.9m 2 in area,and the distribution density was 22.99t/m 2 in area within three sub areas of the distribution of krill in the year 1991/1992.The standing crops in the 125740.7m 2 of surveyed areas was 4.043×10 6 tons,with an average of distribution density 32.15t/km 2 in 1992/1993.