GROWTH AND SHRINKAGE OF ANTARCTIC KRILL EUPHAUSIA-SUPERBA FROM THE INDIAN-OCEAN SECTOR OF THE SOUTHERN-OCEAN DURING SUMMER

Growth rates of Antarctic krill Euphausia superba Dana in the Indian Ocean sector of the Southern Ocean were measured in 4 summers. Growth rate was measured using an 'instantaneous growth rate' technique which involved measuring the mean change in length of the uropods at moulting. In the first 4 d following collection mean growth rates ranged from 0.35 to 7.34 % per moult in adults and 2.42 to 9.05 % in juveniles. Mean growth rates of adult and juvenile krill differed between areas and between the different years of the investigation. When food was restricted under experimental conditions, individual krill began to shrink immediately and mean population growth rates decreased gradually, becoming negative after as little as 7 d. Populations of krill which exhibited higher initial growth rates began to shrink later than those which had initially been growing more slowly.