CCAMLR

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.

The CEMP Standard Methods for monitoring foraging trip duration in Macaroni Penguins recommend using only males. However, males attend the chicks at the nest during most of the brooding period, while the females make frequent foraging trips. We analysed data from 17 males instrumented with VHF-transmitters in the middle of the brooding period (chick age 12-18 days) and 17 females instrumented at the start of the creching period (chick age 25-30 days). Males made their first foraging trips at the start of the creching period. The first trip usually lasted several nights, whereas the subsequent trips were shorter (average 21.8 h). Female foraging trips averaged 27.2 h. No apparent changes in the foraging trip duration of either sex as a function of date were recorded during the creching period. Female attendance periods in the colony where shorter (average 11.9 h) than those of males (average 21.4 h), and females made more foraging trips than males. These results suggest that females might be more appropriate than males as the subjects when monitoring foraging trip duration. In addition, the fact that females spent more time foraging and conducted more foraging trips than males might suggest that female foraging trip duration is more sensitive to changes in prey availability.