CCAMLR

During the period March to May 2000, the UK undertook trials of a pot fishing method to catch D. eleginoides around South Georgia (Sub-area 48.3). This method has the potential to minimise, or eliminate, incidental bird mortality when compared to the standard longline method. This paper describes the trial, the results, and discusses the commercial viability of this fishing method for toothfish fisheries in the CCAMLR area. While the method successfully caught D. eleginoides, there was a large bycatch of crab species. The catch rate of toothfish was notably lower than that achieved in the longline fishery. Importantly, the use of pots eliminated bird bycatch. To capitalise on this feature, there is a need to improve the commercial viability of the method and minimise the quantity of bycatch. A number of potential changes are suggested to this end.

Morphological information is given on specimens of Raja georgiana that were caught during a demersal trawl survey in Subarea 48.3, South Georgia. It is concluded that, in spite of allometric growth, proportional measurements are best referenced to total length rather than disc width. Additional biological information is given: total mass=0.00000646x(total length)3.06. Based on data from male fish, they are thought to mature at about 800mm total length.

A survey was conducted by the UK around South Georgia and Shag Rocks, Subarea 48.3, from 11 January to 2 February 2000, using the FV Argos Galicia. The design followed similar surveys by the UK conducted throughout the late 1980s and 1990s. The swept area estimates of the standing stock of Champsocephalus gunnari were about 24,800 t. Estimates for other major species are given.

In the period from 11 December 1999 to 31 January 2000 Russian trawler "Zakhar Sorokin" carried out fishing the icefish Champsocephalus gunnari feeding consent rations in the western shelf of the South Georgia Island. Icefish 26-40 cm in length, with the average size of 30.3 cm made up the bulk of the catches. Length-frequency distribution was characterized by bimodality, with frequency peaks under 27-29 and 33 cm for fish aged 3 and 4 years. The by-catch of small size Champsocephalus gunnari (with the length of 24 cm and less) amounted to, on the average, 0.6% per a haul.
The male/female ratio, on the average, equalled to 1/1.2. The active process of gonad maturation, more rapid in females, was observed. In December gonad maturation stages II and II-III and in January - II-III and III, respectively, prevailed.
Icefish feeding intensity remained to be relatively high during all the period of observations. Mean stomach fullness amounted to 2.5. Antarctic krill Euphausia superba, the occurence of which in the stomachs was estimated at 86%, and Themisto gaudichaudii (27.8%), were the main feeding objects.
Mean prevalence and intensity of Champsocephalus gunnari infestation by leech Trulliobdella capitus was 11.9% and 1.3 and by parasitic copepods Eubrachiella antarctica - 37% and 3.

The dynamics of daily vertical migrations of icefish Champsocephalus gunnari was studied and some quantitative estimates were obtained by results of analysis of more than 150 fragments of echograms obtained with the use of an echograph of the "Priboi-101" echo sounder during the directed fishery for icefish in the subarea 48.3 in December 1999 – January 2000. The commercial concentrations of icefish can be considered by the type of the vertical distribution as bottom/pelagic ones, and the pelagic component of their biomass is great either during the night or day time. Of this, it can be concluded that assessments of Champsocephalus gunnari stock based on the results of bottom trawl surveys can be underestimated.

Work on finfish in the southern Scotia Arc was restricted to taxonomy until the end of the 1960’s. Commercial exploitation, primarily on mackerel ice fish, Champsocephalus gunnari, and marbled notothenia, Notothenia rossii, started around the South Orkney Islands (60 – 62° / 43 – 47° W) in 1977/78 and close to Elephant Island and the lower South Shetland Islands (60 – 62° S / 54 – 62° W) in 1978/79. The fishery was lucrative for a few seasons only, and was closed in 1989/90.
Stocks of finfish suffered substantial declines during the period the fishery was open. Most fish stocks, with the exception of mackerel ice fish and marbled notothenia, had recovered from exploitation by the end of the 1980’s/beginning of the 1990’s. Since the early 1990’s, most species appeared to have changed little in abundance, and followed primarily fluctuations in year-class strength and the environment. However, stocks of mackerel ice fish, which had formed the backbone of the fishery remained only small proportions of their initial sizes.
Most information on biological parameters of finfish stocks stemmed from Soviet, Polish, German and recent American research in the area. Two elements of the fish fauna overlapped in the southern Scotia Arc region: peri-Antarctic or Lesser Antarctic species and high-Antarctic species. Peri-Antarctic species prevailed in terms of weight and numbers. High-Antarctic species occurred regularly albeit in small numbers, and played a negligible role in terms of biomass. Among the three subareas, the fish fauna around the South Orkney Islands was the least known. Basic biological parameters of fish species, such as vertical and horizontal distribution, reproduction, age and growth, food preferences and feeding (except in the South Orkney Islands) were comparatively well known although some gaps in our knowledge still existed. Age and growth of most species were poorly understood. Major deficiencies were apparent in the understanding of the early life history of many species. Future work should focus on filling in the gaps in the biology of species, intensifying synecological work and better describing the relationships of fish species with each other, predator-prey relationships both with other fish species and seals and birds, the food consumption of fish species, and their interactions with the environment.