Spatio-temporal variability in stock structure of female Antarctic krill (Euphausia superba) in the Scotia Sea, Antarctic

Abstract:

The Scotia Sea is the most densely distributed area of Antarctic krill (Euphausia superba) resources, and is also the traditional fishing ground for krill fishery, but population structure of krill is complex and varies widely in this region. It plays the key role of females in the population for stabling structure and maintaining size of population. In order to understand the population dynamics of krill in this region, the temporal and spatial variability in female stock of krill resource in this region was analyzed using samples randomly collected by fishery surveys from January to September, 2016 to 2022.The results showed that there were significant differences in the development stages of krill annually. During 2016-2022, female krill stock was mainly dominated by subadults, followed by adults, and the proportion of juveniles was low. For the perspective of the annual variation of sexual maturity, the proportions of subadults(stages 2FC and 2FD) were generally higher than that of stage 2FB individuals.In terms of seasons, the female stock structure was relatively simple in winter and spring, while that was very complex in summer and autumn, the subadults was predominant in the stock. In addition, the structure of female krill stock was different between regions, the proportion of adults in the South Orkney Islands was the highest (65.4%), while the subadults was predominant in the stock (89.9%) and no juveniles occurred at South Georgia.