CCAMLR

This two-page flyer targets commercial longline fishermen in Alaska. Aspects of the streamer line developed in the course of research in Alaskan demersal longline fisheries are described including materials and performance standards.

Aspects of the ecology of the Bigeye grenadier, Macrourus holotrachys caught as bycatch in the Patagonian toothfish longline fishery conducted around South Georgia were investigated. Age estimates suggest that M. holotrachys is a long lived and moderately slow growing species, reaching ages of over 30 years and attaining lengths in excess of 80cm (Lt). Von Bertalanffy growth parameters were estimated for females and closely matched those of the congeneic species M. berglax from the Northern hemisphere. The size at which 50% of females had started to mature (Lint 50) for M. holotrachys was 21cm (Lpa) and occurred at around 9 years old. Estimates of natural mortality and Pauly’s growth performance index were found to be low (M= 0.09 And ? = 2.82 respectively). Gonad maturity stage was described from macroscopic and histological investigation. Mature ovaries had oocytes at all developmental stages with between 22 and 55% likely to be spawned each year. Absolute fecundity ranged from 22,000 to 260,000 eggs, an average number for a macrourid of this size. A highly skewed sex ratio of 33:1 females: males was found for specimens caught by longlines but not for shallower trawl-caught specimens (1:1). It is suggested that females are far more susceptible to longline capture than males. M. holotrachys is a bentho- pelagic predator/scavenger that feeds on a wide range of fish and invertebrates.

This was the first deep-water trawl survey of the South Georgia Maritime Zone funded by the Government of South Georgia and the South Sandwich Islands (GSGSSI) as part of the South Georgia Project. The survey was focused primarily at providing new information on the distribution, biology and ecology of Patagonian toothfish (Dissostichus eleginoides) at South Georgia as well as providing information on bycatch species of the longline fishery, particularly grenadiers (Macrourids) and Skates (Rajids). A further key aim of the survey was to employ the AUDOS baited camera system to provide new information on the distribution and behavior of toothfish and other species found over the shelf edge at South Georgia.
The primary objectives of the survey were to: -
• Determine toothfish distribution and population structure in the South Georgia and Shag Rocks regions;
• Provide further information on the biology and ecology of toothfish;
• Commence tagging studies on rajids to contribute to our understanding of their stock structure, migrations, and growth;
• Investigate the biological characteristics of potential relevance to stock dynamics for all fish species in the area including by-catch species of the longline fishery ie macrourids; and
• Deploy AUDOS to investigate the distribution of toothfish at depths beyond which fishing is
undertaken

A dietary overlap analysis between notothenioid species was carried out among three fish assemblages at the South Shetland Island area. Using tyler’s (1972) method, the reoccurrence of main and secondary prey among fish predators was 33% in summer and 37% over the year at Potter Cove; 25% in summer and 7% in winter at Admiralty Bay; and 20% in autumn/winter around Elephant Island. Likewise, using the “S” index of Linton et al. (1981) the diet similarity between most species pairs is

Notothenia rossii was the first target species of the fishery in the Southern Ocean. The species has been heavily fished at the beginning of the 1970’s. The closure of the fishery for this species was one of the first conservation measures CCAMLR adopted in 1985. Fish biomass within a CCAMLR Subarea or part of a subarea is commonly estimated targeting a number of species including N. rossii at the same time. These surveys are conducted under the assumptions that the target fish species are more or less evenly distributed over the area at the time of the survey. This assumption is violated in the case of N. rossii which shows an abundance which is extremely skewed in that a large proportion of the population tends to aggregate in small areas while most of the area of distribution is only thinly populated. In order to provide more accurate estimates of the species it is suggested that an acoustic survey combined with a number of identification hauls might be the most promising approach to estimate biomass of N. rossii more adequately.

A previously un-described population of black-browed albatrosses (Thalassarche melanophrys) is reported at the Evangelistas Islets, Straits of Magellan, Chile. The population was censused from aerial photographs taken on 13 October 2002 which yielded an estimate of the number of breeding pairs. A combined total of 4,670 pairs of black-browed albatrosses were found nesting at Elcano and Lobos Islets, two of the four islets in the Evangelistas group. This new record raises to four the number of breeding islands of this albatross species in Chile.

The diet of black-browed albatrosses was studied at Gonzalo Island, Diego Ramirez, Chile, during the early chick-rearing period of 2000, 2001 and 2002. Diet composition was determined by sampling chick stomach contents during January and February of each year. Reconstituted meal mass was similar throughout the study, with diet being dominated by fish in all three years. Overall, the main items taken were the fishes Macruronus magellanicus (66-89% by mass) and Micromesistius australis (2.6-3.7% by mass), which are both fisheries-related species, and the squid Martialia hyadesi (8-20% by mass). The distribution of the prey species indicates that black-browed albatrosses obtained the bulk of their food over the South American continental shelf, but also foraged at the Antarctic Polar Front. The prevalence in the diet of fish species discarded from fishing operations, and the presence of fish hooks and fish bait species, indicates a strong association with fisheries in southern Chile.