CCAMLR

A method of calculating fishing mortalities which will allow depleted fish stock to recover to levels near those giving greatest net annual increment within two to three decades is illustrated. These fishing mortalities are based on probabilistic descriptions of the future states of a depleted stock, and take into account uncertainty in assessments. Sample calculations show that applying a policy of F0.1 will not always lead to stock recovery in two to three decades, and hence that additional management policies are required for depleted stocks. The implications of these studies for defining the terms ‘depleted’ and ‘target levels for recovery’ are briefly discussed

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.

In December 1989/January 1990 main krill concentrations along the Antarctic Peninsula occurred NE and SE of Elephant Island, north of the South Shetland Islands, in the central Bransfield Strait and in the SW shelf waters. Mean biomass was 10.1 tonnes per nautical square mile, i.e. an estimated stock biomass of 950,000 tonnes. The zooplankton, however, was dominated by salps in the entire region.
The krill stock consisted of subadult and adult stages. Nain concentrations of gravid females were detected north of the South Shetland Islands. No spawning occurred in the Bransfield Strait and in nearshore waters of the SW shelf regions. Juvenile age group 1+ was almost absent from all samples, indicating a poor 1988/89 year-class.