CCAMLR

Positions of commercial krill operation for 1980/81 season to 1998/99 season in the area to the north of South Shetland Islands were analyzed by using GLM (generalized linear model). Fishing season, the timing, and the longitude were significant factors to explain the variability of latitudes where operations were undertaken. Operations tended take place in the north in early 1980s, but from mid-1980 onwards, they tended to happen in the south, with exceptions of 1994/95 and 1995/96 seasons. Predicted latitudes of operation significantly correlated with Salp densities in the Elephant Island area (Spearman's rank correlation , p<0.05), but not with krill densities. This may be due to the intention of fishing vessels to reduce the salp in the products.

Scientific observations on fishes and salps incidentally caught during commercial krill fisheries by F/V Niitaka Maru were made from 3 January to 4 February 1999 in the vicinity of the South Shetland Islands. Among 74 net hauls quantitatively examined, only a total of 5 specimens of juvenile fishes belonging to three notothenioid species, Notothenia coriiceps, Chaenocephalus aceratus and Chaenodraco wilsoni were found in 4 trawl catches. On the contrary, salps were captured as by-catch in 69 hauls and those estimated value was 20 to 3560 ind./t of krill. By-catch fishes fed on Thysanoessa macrura and Euphausia superba was not found in their stomachs. Abundance of salps in krill catches could have been depended on the density of krill concentration. At least, the large incidental catch of salps (>2500 ind./t of krill) occurred in hauls with the low krill catch rates (

To estimate the abundance and distribution of Antarctic krill (Euphausia superba) in the vicinity of South Shetland Islands (SSI), a hydroacoustic/oceanographic survey was conducted by the R/V Onnuri from 9 to 19 January 2000. The acoustic data were obtained using a Simrad EK500 echosounder operating at 38, 120, and 200 kHz, from 8 transects comprising the South Shetland Islands (SSI) mesoscale box (total transect length = 459 nautical miles, area = 11,313 n mile2). Krill were collected with a Bongo net (mesh size: 0.333 mm, 0.505 mm) to determine their size composition and stage of development. In addition, Conductivity, Temperature and Depth (CTD) and on-station Acoustic Doppler Current Profiler (ADCP) were deployed to understand the physical structure of the water column at 11 stations.
The hydrography was differentiable between the offshore region and coastal area. Offshore stations showed the presence of ‘Winter Water’ in mid layer and Circumpolar Deep Water at greater depths. Offshore water and coastal water were also seen to the north and south of Elephant Island, respectively. ADCP results indicate the water flowing from the Bransfield Strait out to the offshore region around the east of King George Island.
The length-weight relationship of krill sampled during the survey was w = 0.0035*(L)3.2108 where w was the mass (mg) and L was the total length (mm) ; the median length was 50 mm. The conversion factor for integrated backscattering area to areal krill biomass density at 120 kHz was 0.1556. The mean density of krill near the SSI area was 12 g/m2 with a coefficient of variance (CV) of 14.5%. The mean density and CV in the Bransfield strait was 9 g/m2 and 20.3 %. Krill swarms of relatively high densities occurred to the north of Smith Island, north and east of King George Island and north and south of Elephant Island.

Research on water structure and dynamics, krill biomass assessment, biology and distribution were carried out in two standard boxes on the shelf and slope northwest and northeast of South Georgia. Eight hydroacoustic transects with hydrographic stations and RMT8+1 trawls were carried out in each box. Krill were distributed rather evenly throughout both boxes, but no dense concentrations were apparent. In the western box krill density was nearly 0.2 glm3 and in the eastern box was 1.8 - 4.7 glm3 • Juvenile krill of 30-36 mm length were observed in the shelf zone and larger specimens, including spawning and posts pawning females of 50 mm and larger, were distributed in slope zone and deep oceanic waters. According to these preliminary results, krill abundance on the South Georgia shelf in January 2000 was lower then usual and no concentrations suitable for commercial fishing were observed. Temperature and salinity measurements carried out on the standard hydrographic stations revealed oceanographic conditions were similar to the long term mean values. However on this survey we did not observe any of the usual gyres or eddies which lead to the formation and maintenance of krill concentrations.

The paper covers the-results of an acoustic estimation of distribution for krill and non-krill zooplankton within the area of South Sandwich Islands that has been obtained with multy-frequencies algorithms according to the data on survey by Russian vessel ATLANTIDA under CCAMLR Survey-2000. Distribution of acoustic characteristics for krill and non-krill fractions of antarctic zooplankton has been compared. It has been showed that within the field locations occupied by waters of the Weddell Sea and Frontal Zone of Weddell Gyral the bulk of zooplankton had been made of krill, while non-krill fraction dominated in water masses of the Antarctic Circumpolar Current.