A Concept of Seasonal Variation of Krill (Euphausia superba) Distribution and Abundance West of the Antarctic Peninsula

Abstract

Data from six expeditions to the Antarctic Peninsula (from 1977 to 1986, in the months of October through June) were analyzed to obtain a general picture of the seasonal variability of krill distribution and abundance. In summer, during the spawning season the krill stock shows a spatial succession of developmental stages along the Peninsula from inner shelf (juveniles) to oceanic waters (adults). A temporal succession of abundance is observed from early spring (mostly juveniles) to summer (all stages) in occurrence of developmental stages and absolute krill abundance in the area. Within a given year average krill abundance differs by more than an order of magnitude, depending on the month of sampling, thus masking a possible interannual variability in the Peninsula region. Seasonal fluctuation in abundance and spatial distribution patterns are discussed as possible effects of seasonal changes in the location of the atmospheric pressure zones (influencing currents and drift of krill) as well as migration of krill.