Towards an assessment of the stock of the ommastrephid squid Martialia hyadesi in the Scotia Sea: data from predators

Cephalopod fisheries world-wide mainly target species from two families, Loliginidae and Ommastrephidae. Fisheries for the latter have been characterised by dramatically fluctuating annual catches and frequent switches to exploit new target species. It is likely, therefore, that exploitation of the sub-Antarctic ommastrephid species Martialia hyadesi will be attempted in the future. This squid is an important component of the diet of several species of albatross and the southern elephant seal and is probably taken in significant quantities by several other Southern Ocean vertebrate predators. Estimated annual consumption by known predators in the Scotia Sea is 326098 - 330642 tonnes, 94% of which is taken by southern elephant seals, and the other species may take at least a further 51400 tonnes. By far the most important consumer is the southern elephant seal which is estimated to consume 308016 tonnes per year. The proportion of total annual production of Martialia taken by predators cannot be estimated but it may be relatively small unless they primarily consume post-spawning, moribund squid. At least for the albatrosses and southern elephant seal this does not appear to be the case. Martialia probably has a life span of two years and a circumpolar distribution but its biology and ecology are still virtually unknown. Given the commercial potential of the Southern Ocean stock of Martialia and its significant role in the diet of some vertebrate predators the species is clearly important within the context of the aims of CCAMLR and should attract greater research effort in the future.