Aspects of the Roles of Squid in Food Chains of Marine Antarctic Ecosystems
Squid (Cephalopoda) are important organisms in marine food chains. However, there are very few studies of their ecological roles in marine ecosystems of the Antarctic. Seventy-six specimens of squid, both large (ca 355 mm in mantle length) and small (ca 40 mm), have been collected by large mid-water trawl operations of the Japanese pilot fishery for Antarctic Krill, Euphausia superba, in the Antarctic during 1980–81 and 1981–82. The squid collected are all considered to be young juveniles distributed at shallower depths than adults. Two species, Kondakovia longimana and Moroteuthis knipovitchi, are dominant. Alluroteuthis antarcticus, Pholidoteuthis boschmai, Brachioteu this picta and Galiteuthis glacialis also occurred in the collections. These squid consume various kinds of food, but they feed mainly on macro-zooplankton and micro-nekton. Krill is the main food item of squid in the Antarctic. An amphipod, Themisto gaudichaudii, is also a major component of the food of Kondakovia longimana. Small euphausiids, Thysanoessa macrura, and large chaetognaths, Sagitta gazellae, are also found in the stomachs of K. longimana, which indicates that the species is a plankton feeder. Fish are considered to be a major food item for Moroteuthis knipovitchi, together with E. superba. Cannibalism appears to be rather common in these squid. Predation by deep-diving Sperm Whales, Physeter catodon, on squid larger than 400 mm in mantle length was observed, and this, associated with the fact that such large squid were not caught in mid-water trawls, suggests that squid are segregated into different water depths according to size and maturity in the Antarctic.
KeywordsStomach Content Sperm Whale Antarctic Krill Mantle Length Euphausia Superba
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