Geographical distribution and age composition of Euphausia superba larvae (Crustacea: Euphausiacea) in the South Shetlan
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Geographical distribution and age composition of Euphausia superba larvae (Crustacea: Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions GAO Qian1 , XU Zhaoli1 , HUANG Hongliang1 , CHEN Xuezhong1∗ , FENG Chunlei1 , LI Lingzhi1 1
Key and Open Laboratory of Marine and Estuarine Fisheries, Ministry of Agriculture, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China
Received 18 June 2012; accepted 15 July 2013 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2013
Abstract Spatial distribution patterns of the different life stages of Euphausia superba in the region of the South Shetland Islands and southern Scotia Sea (Antarctica) were assessed based on scientific survey data collected in January and February of 2010. Adults, eggs, nauplii, metanauplii, calyptopis I–III, and furcilia I–II were found in the investigation. The abundance of larvae averaged 1 172.8 ind./m2 , with calyptopis I and II as the dominant stages. Habitat occupancy patterns varied among Euphausia superba at different stages, and three sub-regions were identified by cluster analysis. The degree of larval development increased from west to east. Larvae were not observed north of the South Shetland Islands. Calyptopis I was predominant in the water between Elephant Island and the South Orkney Islands, which featured no thermocline. Older stages, including calyptopis II and III and furcilia I and II, were common in north and northeast of the South Orkney Islands, which were characterized by high temperature and high chlorophyll concentration. Distribution and abundance of the early life stages of E. superba were associated with specific environmental conditions. According to Biota–Environment matching (BIOENV), the distributions of E. superba larvae were correlated with a combination of temperature at the surface and 200 m, and 0–100 m integrated chlorophyll a concentration. Key words: Southern Ocean, Euphausia superba, larvae, distribution pattern Citation: Gao Qian, Xu Zhaoli, Huang Hongliang, Chen Xuezhong, Feng Chunlei, Li Lingzhi. 2013. Geographical distribution and age composition of Euphausia superba larvae (Crustacea: Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions. Acta Oceanologica Sinica, 32(11): 59-67, doi: 10.1007/s13131-013-0378-1
1 Introduction Euphausia superba Dana is a species of high biomass and great importance in the food chain of Antarctica. It serves as the major link between primary producers and vertebrate predators (seals, whales, and seabirds) in the Southern Ocean food web. The species is also commercially important and subject to increasing fishing pressure (Everson, 2000). The fishery for Antarctic krill (E. superba), had been stable at around 120 000 t for 17 years until 2009, but recently has increased to more than 200 000 t, associated with increasing commercial interest in products derived from krill (Nicol e
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