CCAMLR

Results of harvesting operations for Antarctic krill (Euphausia superba) in Fishing Area 58 in the Indian Ocean Sector of Southern Ocean, during the First Indian Antarctic Krill Expedition (27 December 1995 - 10 March 1996) on board FORV Sagar Sampada are summarised in this paper. 18 hauls were made using a 2.5 m Isaacs-Kidd Midwater Trawl (IKMT) in the area 59°00’-61°08' S lat; 30°04'-40°04' E long, from 27 January to 12 February 1996. In the area of operations, krill was caught in waters south of 60° parallel (60°43'-6l°00' S), between 32°00-34°05' E long. Krill were present in 33.3 per cent of the total number of hauls taken. Major species obtained were krill (8%) and salps (92%). Aimed trawling operations targeted at Antarctic krill were conducted using a 42 m commercial krill midwater trawl sourced from Poland and a 49.5 m experimental krill midwater trawl of Danish origin. total catch of 12470 kg was landed during the 16 aimed trawling operations. This included 5637 kg Antarctic krill (Euphausia superba), 6738 kg salps, 35 kg jelly fish, 12 kg krill juveniles, 2.2 kg lantern fish, 5.7 kg squid and 2.7 kg other fishes. Krill constituted 46 per cent of the total catch while salps constituted 54 per cent. Average catch for krill worked out to be 354.6 kg.haul-1. In the area of operations (57°53'- 61°13' S lat and 31°40' - 36°31' E long ) krill was caught between 60°48' - 61°13' S lat and 31°19' - 34°14' E long. Better catches (>l000 kg.haul-1 ) were obtained between latitude 60°40' - 61°13' S and longitude 33°34' - 34°14' E.

During the First Indian Antarctic Krill Expedition (FIKEX), krill samples were collected from 34 stations of fishing area 58 in Indian Ocean sector of Antarctic region between lat.57°53'S to 61°13'S and long.30°02'E to 40°05'E. These were analysed onboard FORV Sagar Sampada for the study of biology, distribution and abundance. The samples were collected for a period of 18 days from 26th January to 12th February '96. Three types of gears were used viz. Isaacs Kidd Midwater Trawl (IKMT), 49.5m krill midwater trawl (Cosmos trawl Denmark) and 42m Polish krill midwater trawl. The length frequency analysis indicated a bimodel distribution with 19-20 mm and 53-54mm as the most abundant size in the fishing area 58. The average sex ratio of male and female Euphausia superba was observed to be 1:l.17 though it differs from swarm to swarm. The analysis showed that 47% of krills with high intensively feeding population and 25% with moderate feeding population which indicate the feeding of krill and availability of food in the area surveyed. Maturity stage IV (fully matured) was maximum among both the sex followed by stage V (spawned), indicating spawning period. Of the total catch of 12.470 tomes recorded, krill constituted 45.6% and the by-catch 54.4%. The by-catch included salps 54%, Antarctic squid 0.07%, jelly fish 0.02% and fin fishes 0.13%.

On the basis of acoustically registered krill swarms along a 1097 nm transect in the area 58 of Indian Ocean Sector of Antarctic region, the biomass density of krill, their spatial and depth distribution are presented. The mean density of krill biomass between 60°00'S and 61°00' S parallels 34°00'E and 40°00'E meridian was recorded as 0.6t.km-2. Presence of krill was not observed north of 60°00' lat. Factors which influence the abundance of krill in the area are discussed. Different forms of krill swarms observed during the survey are illustrated and defined.

Distribution, abundance and species composition of zooplankton collected during the First Indian Antarctic Krill Expedition were studied. Zooplankton biomass values ranged fiom 9.79 to 303.62m1./100m-3 (x=142.14±77.02). High standing stock values were recorded in the study area where copepods, chaetognaths, euphausiids and salps were the dominant taxa. Copepoda formed the major constituent of zooplankton community and the population density ranged fiom 650 to 7209/100 m-3 of zooplankton catch. Swarms of krill and salps were observed during the study period (austral summer) which were the prime cause for high standing stock of zooplankton. The prevailing physical parameters could be the important factor influencing the higher standing crop of different zooplankton groups. The study revealed that the present investigation site falls under potential krill fishing ground.

Investigations on krill trawl operations in the southern ocean were accompanied by the phytoplankton and zooplankton studies during the First Indian Antarctic Krill Expedition. The study area which lies between latitude 56° to 61° 17's and longitude 30° to 40°E is characterized by cold surface waters with temperature ranging from 0 to 3° C and high nutrient content. Phytoplankton cell counts in surface waters ranged from (1.92 to 21.89) x l04 cells/litre. Phytoplankton cells represented 33 species, consisting of 32 diatoms and one dinoflagellete. Chaetoceros and Nitzschia spp. dominated the phytoplankton organisms. The other common diatoms present during the studies were Navicula, Rhizosolenia, Leptocylindrus and Corethron criophilum. Calm sea state prevailing from 27 January to 11 February favoured proliferation of certain phytoplankton species to bloom condition.
Zooplankton biomass showed wide fluctuation, with values ranging from 9.8 to 303.7m1/100m3. While the total catch per (IKMT) trawl ranged from 0.2 to 2400 kg, the percentage of kill occurrence varied from 0 to 100% at stations sampled. The fluctuations in phytoplankton and zooplankton standing stocks followed a similar trend. Marked drop in phytoplankton and zooplankton in the region of krill swarm however showed active feeding by the latter on these planktonic communities. The results indicate that areas favouring phytoplankton blooms and zooplankton abundance could be possible sites for locating krill fisheries in the southern oceans.

Proportional recruitments (R1 and R2) were calculated for Subareas 48.1, 48.2 and 48.3 from logbook data of Japanese commercial krill fisheries during 1980 to 1997. Inter-annual patterns of R1 and R2 in Subarea 48.1 generally showed similar trends to Siegel et al. (1 998)'s values around the Elephant Island. However, the values especially R1 in this study were extremely smaller than Siegel et al. (1 998)'s values. This may be due to the net selectivity and/or incomplete coverage of the distribution of small krill by commercial fisheries. Inter-annual pattern of R1 and R2 in Subarea 48.2 showed somewhat similar pattern to Subarea 48.1. However, because of inconsistency of the operation periods and occasional small sample size, interpretation of it's pattern in this Subarea should be dealt very carefully. In Subarea 48.3, R1 values showed the evidence of recruitments in two year classes, which coincided with the year classes of strong proportional recruitments in Subarea 48.1. However, the complexity of length composition in this Subarea was also pointed out.

In the paper the results of the investigations on three mesoscale surveys covering wide area of krill between Antarctic Peninsula and South Georgia Island are considered. Surveys including from 158 to 202 stations were carried out by Soviet research vessels in summer-autumn periods of 1983/84 and 1987/88 and in a spring period 1984/85 by a standard grid of stations according to the standard method by Isaacs Kidd Midwater Trawl in the layer 0-100 m. Krill biomass distribution (g/1000 m3) and its mean values were analysed by Subareas (48.1, 48.2 and 48.3) and for the whole area investigated. The results of surveys confirm modern understanding of general pattern of krill distribution and drift in the western part of Atlantic sector of Antarctic (e.g.: Priddle et al., 1988; Makarov, 1996). The most spatial-temporal stability of the krill distribution field with more higher biomass of aggregations was observed in the western part of the area from Antarctic Peninsula to the eastern part of the South Orkneys area. The most variability of krill distribution in spatial- temporal survey scale, which is characterised by biomass change more than two orders of the magnitude in different seasons, was observed in the region of South Georgia and adjacent waters of the Scotia Sea (Subarea 48.3). Possibility of krill transportation into the region of South Georgia is considered. It is indicated that absence of krill in the Island region at the season of 1983/84 was stipulated exclusively unfavourable oceanological conditions (absence of water flow from south areas). It is also indicated that krill absence in the eastern part of the Scotia Sea may cause its absence in the region of South Georgia independing of favourable oceanological conditions (spring-summer period 1983/84). The possibility of recruitment of the krill stock in the South Georgia region from the central part of the Scotia Sea is considered. The analysis of variability of mean biomass by areas and by seasons indicates that trend of krill abundance and biomass, obtained in the Subarea 48.1 lately (Siegel et al., 1997, 1997a) is not revealed on the whole survey area. The total biomass index in the studied area during all the seasons remained at the same level (76.5-101.7 g/1000m3).

Polynyas accelerate oceanic and atmospheric processes. We additionally think polynyas influence biological activity. We pursued daily transition of polynyas in the Ross Sea, Antarctica from 1978 through 1994 using images of sea ice concentrations by the satellite microwave observations. A typical polynya existed in the inner area of the Ross Sea in November of the each year. The shape of the polynya changed remarkably in several days. The polynyas have the range of approximately 500 km from the bottom to the entrance of the Ross Sea. The polynyas usually open to the northern oceanic water late in December in each years except 1982, 1988 and 1992.

Acoustic data from the Polish FIBEX survey in the West Atlantic were examined to check the consistency of krill abundance estimates against the results of the other FIBEX survey vessels. The results indicated that there was a high level of consistency between the results from the Polish vessel and those from the other vessels that operated in the Peninsula region and in the West Atlantic.

Size fractionated chlorophyll-a concentrations of surface seawater was measured (pico-, nano-, and micro-size fractions) during commercial krill operations in the waters north of the South Shetland Islands from late December, 1991 to mid-February, 1992. The proportion of green krill had significant regressions with chlorophyll-a concentrations in micro and nano- size fraction. This result shows the importance of micro- and nano-size phytoplanktons in terms of food source for the Antarctic krill in the natural environment.