CCAMLR

On the grounds of materials collected by biologists-02servers from October 1989 to June 1990 near South Orkney Islands the growth of males and females are characterized according to size groups, distinguished using the probability paper. Six size groups both for males and females were distinguished. Period of the intensive growth of the males continued from December to April, and for the females from November to February. The males increased their size for different size groups by 7-10, females by 8-10 mm. The rate of growth for the males was higher among the small specimens and vice versa for the females. Growth rates are similar to those observed in 1984-1985 in the South Orkneys and in the Admiralty Bay (King George Island).

Temporal and spatial variability of krill distribution characteristics was investigated in an 8 x 6 mile micropolygon, where eight consecutive hydroacoustic surveys were carried out. Krill aggregations occurred a s fields of small swarms whose spatial distribution characteristics (size and density of swarms, swarm field density, number of swarms per mile) varied considerably from tach to tack within each survey. The maximum horizontal extension of swarms was 120 m, although about 70% of swarms were of 30 m in length, with density up to 200 g/m3. About 75% of all swarms revealed biomass to be less than 1 tonne. Average statistical parameters of swarms in the polygon varied insignificantly from survey to survey, while the swarm number varied within the board range from 1 918 to 7 000 and further to 1 554 units. Krill biomass in the polygon varied spasmodically within the range from 1 091 to 6 085 tonnes. Krill distribution variability revealed in the polygon suggests an irregular import and export of krill from the polygon due to transport by the current. Additionally, in the upper layer of 0 to 50 m swarm number was almost constant, and krill redistribution due to transport and diurnal migrations occurred in the layer of 50 to 150 m. Estimated velocity of krill swarm displacement corresponded to the estimated water transport velocity in the polygon, suggesting that passive krill transport occurred.

The mathematical model of a fishery object contact against a mesh, while escaping through a trawl chafer, is presented. Based on it t the equations are provided to calculate the object elimination probability caused by cath and mortality in fishery operations. The coefficient of trawl ecological safety is offered, which is the ratio of the amount of the objects caught and objects caught and died during fishery. The equations are presented to estimate the gross removal of an object by the fleet group. Mathematical model is illustrated by a numeric example from the krill fishery. Thus, the calculated gross removal estimate exceeded the catch rate, based on commercial data in December 1984 in the South-Shetland area, only in 1,5 - 26 %, depending on the fishing intensity, i.e. it was within the range of stock estimate bias.

This paper describes the usefulness of satellite ocean color remote sensing in the Antarctic Ocean by making a comparison between CZCS chlorophyll images and ship-measured chlorophyll concentrations in the sea area off Enderby Land, Antarctica. In addition, some characteristics of the chlorophyll distribution in the Antarctic Ocean are briefly explained by means of the three-month(January-March) composite images.

The main aims of CCAMLR are reviewed in an essay which discusses the advances in the effectiveness of harvesting, arising from developments in science and technology in comparison with the requirements of science to provide information for rational management. It is concluded that co-operation is essential between fishermen and scientists to ensure the provision of the data needed to test hypotheses related to the functioning of the Southern Ocean ecosystem. Although currently co-operation is fairly good it would be improved by an increased spirit of trust between the various parties.

Data from the FIBEX acoustic survey in the West Atlantic sector have been re-examined to check the consistency of krill abundance estimates derived from different survey vessels. There is a good level of consistency between the results from four of the vessels, Itzumi, Dr Eduardo L Holmberg, Odysee and Walther Herwig. While there is an error factor due to the combination of data collected at 50kHz (Walther Herwig survey) with data collected at 120 kHz (all other vessels), it is concluded that this does not materially affect on the estimated biomass.
The data from the Profesor Siedlecki survey do not provide estimates that are consistent with the other surveys. The authors can find no explanation for this difference.

Foregut contents of the Antarctic krill Euphausia superba Dana which were collected in the South Georgia area in austral winter, 12 July ~ 4 August 1992 were observed. A total of 130 individuals (adults: 78, subadults: 49, juveniles: 3) which were caught by krill trawling from various depths were examined in this study. The foregut contents of the krill consisted of various fragments of crustacean zooplankton in 77 individuals out of 130 examined. Among the fragments a portion of the pereiopods of krill was found from all specimens examined. Although the obtained materials were geographically confined to the South Georgian waters, which was free from fast ice throughout the year, the results might imply that E. superba seemed to seasonally switch their food source: E. superba demonstrated herbivorous food habits during the rich phytoplankton bloom, but might change to carnivorous habits in the fall and winter. Strong cannibalistic food habits during austral winter as found in this study are considered to be important aspects for the population dynamics of krill.

The implications between a regional and whole distribution of the Antarctic krill, Euphausia superba DANA, and its environmental gradients in the summer season were considered. In order to find out the relationship between the geographical distribution of E. superba and its oceanographical gradients, an environmental index was introduced. The environmental index was the integrated value of water temperature from the surface to 200m in depth Z. As the results, the area of the high concentration of E. superba coincided with the area of low values of Q 200 chiefly falling in the range from 0°C to –1.5°C where showed the thick Winter Water, especially the area of the Slope Water and the Shelf Water south of the Antarctic Divergence zone.

Annual primary production of ice algae and phytoplankton under fast ice near Syowa Station (69°00'S, 39°35'E), Antarctica, was estimated. Mean daily production in each month from February 1983 to January 1984 was calculated with a mathematical model based on measured parameters of solar radiation, day length, attenuation coefficients of snow, ice and water, chlorophyll a standing stock, quantum yield for photosynthesis etc. Solar radiation measured at Syowa Station ranged from 0 E m-2 h-1 in June to 13.3 E m-2 h-1 in December. Relative light intensity estimated at the bottom of sea ice during the year ranged from 0 to 6.5% of incident solar radiation, due to attenuation with snow and ice. Maximum daily production of ice algae (34 mgC m-2 day-1) and phytoplankton (450 mgC m-2 day-1) was reached in December and in February, respectively. The estimated annual production of ice algae and phytoplankton was 3.5 and 17 gC m-2, respectively. These results indicate that summer phytoplankton production contributed remarkably to the primary production in the coastal ice-covered area near Syowa Station.

Relationship between food environment and maturity of krill around the South Shetland Islands is discussed. Data during 91/92 austral summer shows that when chlorophyll concentration in fraction larger than 2um was high, feeding activity of krill was also high in the natural environment. 5 years data from commercial krill trawlers indicates that percentages of occurrence of gravid female was high when the feeding activity of the krill was high through out the season.
Therefore, interannual fluctuations of maturity populations are governed by the food environment, the phytoplankton stock in the size fraction larger 1 in krill namely by than 2um.