The distribution and demography of Euphausia superba in Prydz Bay during the austral summer 2002

Abstract

This study documents the horizontal distribution and demography of Antarctic krill (Euphausia superba Dana), collectedusing trawls, from the Prydz Bay region during January 2002. Euphausia superba (E. superba) was distributed primarilysouth of 64°S. The average density and biomass were estimated as 68.85 ind·(1 000 m -3 ) and 24.16 g wet weight·(1 000 m -3 ), respectively.Highest values were located in the open sea (depth > 3 000 m). Body length of E. superba ranged from 30 to 55 mm(N=1 758), with a mean length of 38.45±3.68 mm (SD). The overall sex ratio was approximately 1∶1, 47.6% females (41.9%sub-adults and 5.7% adults), 46.6% males (42.7% sub-adults and 3.9% adults), while 5.8% were juveniles. The population structureof E. superba exhibited geographical variation. At stations in the western part of the survey area populations had a high proportionof juveniles, a lower sexual maturity stage for males and small body size, while the opposite was found at stations in theeastern part. A latitudinal difference was found at stations along 70.5°E and 73°E transects: body length was small and the sex ratiowas high in regions of high latitude, while the opposite occurred in areas of low latitude.