CCAMLR

The foraging ranges of six female and four male Adélie penguins breeding at Bechervaise Island near Mawson Station (Mac. Robertson Land) were determined by satellite tracking, using the ARGOS system. Birds were tracked over four foraging trips (by 2 females and 4 males) during the incubation period (November-December 1991) and 17 trips (by 4 females and 2 males) throughout January 1992 when birds were feeding chicks. Most birds made foraging trips to the continental shelf break (1000m isobath) approximately 110 km distant at its closest point. Birds feeding chicks also made journeys of 1-2 days ranging up to 12 km after 17 January when the sea became ice free to the coast. Concentrations of krill Euphausia superba which have in the past been the subject of a fishery occur along the shelf break zone where the birds were foraging. There is potential therefore for overlap between the foraging range of Adélie penguins breeding along the Mac. Robertson Land Coast (approximately 150000 pairs) and any future harvest of krill in the region. The foraging range of the birds at Bechervaise Island considerably exceeds the 15-50 km determined for birds in the South Shetland and South Orkney Islands and reflects the distance offshore of krill one of their major food sources.

Temporal and spatial variability of krill distribution features was investigated at the micropolygon of 8 x 6 miles, where eight consecutive hydroacoustic stations were carried out. Krill aggregations occurred as fields of small swarms of spatial distribution features (size and density of swarms, swarm field density, number of swarms per one mile) varied considerably from tack to tack within each survey. Horizontal extension of swarms amounted to 120 m, however about 70% of swarms were of 30 m in length, with density up to 200 g/m3. About 75% of all swarms revealed bad biomass of less 1 t. Average statistical parameters of swarms at polygon varied insignificantly from survey to survey, while the swarm number varied within the broad range from 1918 to 7000 and further to 1554 units. Krill biomass at polygon varied spasmodically within the range from 1091 to 6085 t. Krill distribution variability revealed at polygon suggests the impulsive nature of krill enter and exit out of the polygon due to its transport by the current. Besides, in the upper layer of 0-50 m the swarm number was a almost constant, and krill redistribution due to transport and diurnal migrations occurred in the layer of 5-150 m. Estimated velocity of krill swarms displacement corresponds to the estimated water transport velocity at the polygon, suggesting the passive krill transport occurred. Krill biomass transported across different tacks also varied spasmodically from survey to survey.

From 18 to 23 April hydroacoustic, oceanological and trawling surveys were carried out within the square of 30 x 30 miles northwestwards of Coronation Island in the fishing fleet operation area. The krill biomass was estimated within the square at the start and the end of works. It amounted to 56.1 thous. t and 61.2 thous. t respectively. During the period remained the hydroacoustic assessment of krill density and oceanological stations were carried out along the square perimeter. Four dublicates of perimeter were made. Control hauls with midwater trawl were made on the regular basis. The average estimates of krill density were obtained by 15-miles intercepts of the perimeter, along with mean water flow and geostrophic currents. The balance of krill input and output for the square was calculated based on these values. In the .first two dublicates the aggregation of krill was observed within the contour and in the second two - loss of krill. The aggregation was 52 thous. t greater than the loss. The researches show that the fishing aggregation stability depends essentially on the heterogeneity of the current's field. The researches were carried out by R/V "Dmitriy Stefanov" owned by PPO "Yugrybpoisk" (Ukraine).

The oceanological, hydroacoustic and trawling surveys were carried out within the polygon of 30 x 30 miles in the fishing area northwestward of Coronation Island in 18-22 April,1992. The krill biomass was estimated in the beginning and at the end of surveys. It amounted to 56.1 and 61.2 thous. t respectively. During the rest of the period the hydroacoustic assessment of krill aggregation density and oceanological stations were carried out along the square perimeter. There were four dublicates of perimeter. The midwater trawl hauls were made periodically. The average estimates of krill aggregation density by 15-mile perimeter sections, average water flow and scheme of geostro-phycal currents were obtained. The balance of krill transport from and into the polygon was calculated. The first two dublicates revealed the krill accumulation in the contour, and the second two showed the loss. The accumulation was 52 thous. t as high as the loss. The researches pointed out that fishing aggregation stability is mainly determined by the water dynamics, such as the availability and duration of heterogenity in the current fields. From 25 to 27 April 1992 three hauls with fishing bottom trawl were made to collect data on size and age composition of icefish, champsocephalus gunnari, green notothenia and yellowfin notothenia over the shelf of South Georgia and Shague rocks. The researches were carried out by H/V "Dmitriy Stefanov" ovmed by PPO "Yugrybpoisk" (Ukraine).

Calculation of drift’s speed (transport with current) of Antarctic krill along the northeastern shore of South Georgia Island (between 54-55S and 34-39W) were carried out. Length of island’s shelf for calculation was assumed about 300 km, but average width of shelf (from shore to 500 m isobate) was assumed about 60 km. Speed of drift in these spatial limits was assumed about 10 cm sec-1. The average density of krill before the beginning of transport along the island’s shore was assumed about 0.1 g m-3.
Total amount of krill immigration on island’s shelf (in above indicated limits) were examined for three main types of water circulation (the typisation according to Maslennikov, 1979).
Duration of krill drift (from the beginning of immigration and to the end of emigration) along the northeastern shore of South Georgia fluctuated from 35-37 days to 75-100 days. For separate cases this duration was valuated as much as 140-150 days (when crustaceans are transported back again on shelf zone at the conditions of the first type of water circulation). The minimal period of krill presence near island is expected for the third type of water circulation, but maximal duration of krill presence here is suggested for the first type of water circulation. Total renewal krill, which is immigrated into shelf waters of island is supposed to take place not less than 2-3 times per year. Peculiarities of accumulation and drift of krill related to the consequence of types of water circulation change are examined.

Data on distribution and biomass of E.superba aggregations at Atlantic sector and near adjacent waters (subregions outside of the Scotia Sea are under pecular attention) are observed° Concentration of E.superba of the same order of biomass volume as in the Scotia Sea were observed at several subregions along the peripherie of Weddell Gyre and also nearshore of Antarctide. Offshore concentrations of E.superba show increased spatial irregularity. Development of fisheries activity in these new for catching areas should include the preliminar getting of knowledges on changeability of E.superba aggregation distribution prior to practical using of observed pattern of that changeability. It requires of additional complex of investigations, which should be directed to the evaluation of drift ways of E.superba as well as related changeability of aggregation location in the open-ocean environment. Exploitation of offshore aggregations of E.superba will be connected with regular search activity prior as well as at the course of every fishery season (year).

Microscale data, described the Soviet krill fishery off the Elephant Island (Subarea 48.1) between 59°-62°S and 53°-57°W during the period from 21.11.1988 to 25.03.1989, are analysed. Though the catch of the USSR in the above-mentioned season reached maximum, the total fishery intensity for the last 9 seasons was low and only 1 standard vessel operated in the area during 40% of the period. The highest catch per-unit-of-effort was observed in January (7.7 t per hour of trawling in average), and the lowest in November (3.5 t per hour of trawling in average). Fisheries tacktics follows the scheme: 1) vessels enter the Elephant Island area and search for krill concentrations; 2) fishing of concentrations, drifted from the Island, and return into the initial area when the concentration has been lost. The velocity of krill concentration northeastward drift, calculated by the fleet displacement amounted to 9.7-11.1 km/day (11-13 cm/sec). The analysis of fishing ground allocation by five-day periods showed that fleet operation areas in general overlap the minor part of foraging zones for animals, preyed on krill. Based on this and taking in account low fishery intensity the conclusion was made that current krill fishery insignificantly affect the seals and birds, preyed on krill.