Attribtuion of acoustic echoes to squid in the south Atlantic
During a research cruise of the British Antarctic Survey ship RRS James Clark Ross in February 1996, more than 2 000 individuals of the ommastrephid squid, Martialia hyadesi, were caught in a single haul made by a pelagic trawl near the Antarctic Polar Frontal Zone in CCAMLR Subarea 48.3. This paper describes the analysis of acoustic data gathered during this haul and a survey of the immediate vicinity, in order to characterise an acoustic signature that may be used to identify this species of squid. Distinctive echoes that did not occur when other, unsuccessful hauls were undertaken, were the only strong echoes recorded from the part of the water column traversed by the net. The trawl was restricted to a single depth zone which reduced the potential number of echoes that might otherwise have been attributed to the squid that were caught.