CCAMLR

We investigated the diets of seabirds at sea in the Antarctic from 1976 to 1988. During the study period, on eight cruises in the Ross, southern Scotia, and Weddell Seas and Drake Passage, we collected or pumped the stomachs of 1,223 seabirds of 23 species. The stomach contents of species that feed below the sea surface contained little plastic, as expected; these birds live entirely on live prey. Among species that feed a t the surface, most of which eat both live and dead organisms, incidence of plastic was highest among the smaller ones and those that are omnivores, or feed on zooplankton and micronekton. This includes the majority of Southern Ocean flighted birds. Incidence of plastic among them was a function of the degree to which their populations frequented waters outside of the Antarctic during the winter. Among those species that live south of the Antarctic Convergence year-round there was little evidence of plastic ingestion. Among those species that are summer visitors to the Antarctic, incidence of plastic in the diet decreased with increased latitude. These results indicate either that the Antarctic Convergence blocks plastic debris, which is commonly found a t the sea surface in the north, from entering the Southern Ocean, or that other factors such as the northward movement of pack ice sweeps the sea clear of plastic. Results also suggest that floating plastic debris is not yet the problem in the Antarctic that it is in more northern waters.

Causes of incidental mortality owing to fisheries activities around Kerguelen (Division 58.5.1) have been identified. The most significant mortality has been noted during directed trawling for Champsocephalus gunnari on the Kerguelen shelf. This is caused by the electrical cable linking the trawler to the trawl (Netsonde system), which mainly affects black-browed albatrosses (Diomedea melanophris). An experimental long-lining cruise in deep waters at the shelf edge also showed the potential impact of this type of fishery if it develops in the Indian Ocean sector of the Southern Ocean. Trammel net fishing for research purposes in the coastal zone does not present any real danger for populations of marine birds and mammals if it remains limited. All types of mortality can be reduced, and ways of doing so are suggested for each fishery.

Antarctic finfish resources have been subject to exploitation primarily by the Soviet Union since more than 20 years. The total yield from the Southern Ocean has been 2.85 million tonnes until the season 1989/90. About two thirds of the catches have been taken in the Atlantic Ocean sector (mainly South Georgia) while the remaining one third originated primarily from the Kerguelen waters in the Indian Ocean sector. The fishery is regulated under the auspices of the Convention on the ‘Conservation of Antarctic Marine Living Resources’ (CCAMLR) for rile whole Southern Ocean since 1982 and under French national jurisdiction around the Kerguelen and the Crozet Islands. Apart from the lanternfish Electrona carlsbergi the fishery on all other species is restricted by conservation measures.
The stocks most heavily affected by fishing are those of Notothenia rossii in both sectors, Notothenia squamifrons in the Indian Ocean sector and of Champsocephalus gunnari in the South Orkney Islands/Antarctic Peninsula region. Sizes of most of these stocks are only small fractions of their initial size. Champsocephalus gunnari around South Georgia has recovered two times from low stock sizes following heavy fishing.

Abstract: Gonad maturation in Antarctic notothenioid fish is a biennial process although spawning is likely to take place annually. However, part of the populations of Champsocephalus gunnari in the Atlantic Ocean sector do not spawn each year. Gonadosomatic index (GSI) of females is 15–40% at spawning. Apart from a few nototheniid species the GSI of males is much less and typi6dlly only 15–20% of that of females. Length at first spawning may be from 55% of Lmax onwards, but in many species it is not attained until 70–80% of the maximum length. The only exception is Champsocephalus gunnari at South Georgia which may begin spawning at about 40% of Lnax. Most species of the Seasonal Pack-ice Zone are autumn/winter spawners, whereas in the High-Antarctic Zone more species spawn in summer and autumn. Spawning time is remarkably constant among populations of some species, in others a latitudinal shift in spawning time is apparent. Fecundity is commonly positively correlated with fish length and weight. It exceeds 100 000 eggs only in a few nototheniid species and is commonly in the order of 1000 to 15–20 000 eggs. Ova diameter varies from 0.8 to 5.0 mm. Egg size distribution among fishes of the Seasonal Pack-ice Zone is bimodal. There is a general trend in nototheniids of increasing egg size and decreasing relative fecundity towards higher latitudes. Incubation time may be up to five months. Eggs of most species are probably left unattended for the long incubation period. Nest guarding has been observed in three species but may be more common in particular among the artedidraconids. A number of reproductive strategies associated with nest guarding, egg size and the duration of the pelagic phase have been identified.