Spatial-temporal variation in population structure of Antarctic krill (Euphausia superba)in the Scotia Sea, Antarctic in 2016.

Abstract

The Scotia Sea occupies the highest density of Antarctic krill (Euphausia superba), which is the traditional fishing ground of krill fishery. However, the population structure of krill differed significantly inter-annually, seasonally and regionally. In order to understand the population dynamics of krill in this region, we analyzed the spatial-temporal variation on population structure of krill using samples collected randomly from fishery survey during January to September 2016. The results showed that sex ratio presented remarkably difference among different months. Females dominated in the population from January to May, but the opposite result occurred from June to September. During the survey period (January to September), juveniles only presented in the January popu-lation, and the percentage of adult females was over 40% and similar to that in February. The proportion of sub-adult females were over 50%, but the proportion of female adults were decreased gradually from March to May. The sub-adult males predominated in the population from June to August. The proportion of sub-adult females increased significantly but the number of male adults decreased in September. Sub-adult females occupied half of population in the Bransfield Strait from February to May. The proportion of spent females (25.6%) was higher than those of individuals with other sexual maturity stages and the gravid females occupied higher percentage of population off northeastern waters of the King George Island in January. From June to September, about half of the population was mature males, but the proportion of mature females was very low off northeastern waters of the South Georgia Island. Maturity stage composition indicated that peak spawning occurred in January and February and that spawning grounds occurred off northeastern waters of the King George Island and in the Bransfield Strait.