Precautionary measures for a new fishery on Martialia hyadesi (Cephalopoda, Ommastrephidae) in the Scotia Sea: an ecological approach

In anticipation of the development of a new fishery for the oceanic squid Martialia hyadesi in the Scotia Sea a revision is presented of annual consumption of the species by higher predators and a brief review is provided of information about the life cycle and distribution obtained from research fishing and commercial catches. The species is consumed by seabirds, seals and whales and the most reliable data are from seabirds because comprehensive sampling can be carried out during the breeding season. A conservative estimate for total annual consumption by higher predators in the Scotia Sea is 245,000 tonnes compared with an upper estimate of 550,000 tonnes if less reliable data are included. M. hyadesi spawns in winter/spring, probably has a two year life cycle and, in common with other ommastrephids, is semelparous. It is proposed that the timing and catches of the fishery should be highly conservative and set with regard to the timing of breeding and consumption rates of the most sensitive of the dependent species. Most predators that have been studied consume M. hyadesi during the first year of its life cycle. Fishing on M. hyadesi after the chick-rearing season of the most sensitive predator (grey-headed albatross) would minimise competition locally and ensure that the fishery only exploited the stock after escapement from most higher predator species. It would also allow monitoring of predation on the stock prior to the fishing season as a form of pre-recruit assessment. Closing the fishery before recruitment of the next generation would ensure availability of prey for higher predators for the following chick rearing season. Preliminary data from a squid jigger undertaking research fishing around South Georgia in June 1996, under the auspices of CCAMLR, provide the basis for assessing realistic potential catch rates.