Antarctic cranch squid - a top predator of the Antarctic waters - its distribution and relationship with Antarctic and Patagonian toothfish

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Mesonychoteuthis is a very big species of squid (maximum recorded weight 498 kg), which hitherto has been caught only very rarely. Soviet and Russian biologists described the morphology of Mesonychoteuthis, calculated its biomass and also created a map defining its habitat on the basis of numerous finds in the stomachs of sperm whales. The material we collected during several assignments as CCALMR observers on longliners reveals a complex food and behavioural relationship between Mesonychoteuthis and Antarctic as well as Patagonian toothfish. When caught on longline hooks, toothfish are obviously exposed to attacks by squid. Our photographic material confirms that Mesonychoteuthis sometimes release their prey only when it is raised to the vesselʹs deck. On the bodies of numerous toothfish deep wounds and marks of large suckers were found. On the other hand, in the stomachs of big Antarctic toothfish pieces and beaks of Mesonychoteuthis were found, one beak having belonged to a squid with an estimated mantle length of not less than 180 cm. Possibly toothfish feed on dead or dying Mesonychoteuthis, but it also might be that the squid itself becomes the prey when attacking large toothfish. Patagonian toothfish with traces of an attack by squid were found not only in the waters around Antarctica to the south of the Antarctic convergence zone, but also to the north of the Antarctic convergence. Therefore we believe, that Mesonychoteuthis may penetrate the northern borders of its usual habitat with waters of Antarctic origin flowing north into the Subantarctic zone.