CCAMLR

Previous studies have established that ocean color information from Nimbus-7/CZCS{Coastal Zone Color Scanner) could be related to distribution of phytoplankton pigment (Chlorophyll-a + pheopigments) concentrations. CZCS data from polar regions have been utilized only a limited number because of many problems as cloud cover, large solar zenith angles, bio-optical algorithm and other logistic constraints. This papar discusses the characterization of phytoplankton pigment concentrations.

The influences of biological and physical factors in the environment upon krill (Euphausia superba) distribution were studies in the area north of South Shetland Islands during 1990/91 austral summer. Krill showed a distinct offshore-inshore heterogeneities in abundance and maturity stage in mid-summer the abundance was low in the oceanic zone (8.5 g/m2), while higher in the slope frontal zone (37.3 g/m2), and the highest along the shelf break (135.1 g/m2) in the inshore zone ; krill were reproductive in the oceanic and frontal zones, whereas non-reproductive in the inshore zone. The following factors were considered to be responsible for this characteristic distribution of krill. Diatoms were the main food of krill, and a spatial correlation between distributions of krill and diatoms were observed. Hence, higher diatom biomass may be one of factors forming krill concentrations in the inshore and frontal zones. The water flow was sluggish in the inshore zone (3.2 km/day), while meandering in the oceanic zone (7.9 km/day) and straightforward in the frontal zone (13.8 km/day). Especially, in the inshore zone, convergent complex eddies were generated along the shelf break, where krill were densely aggregated. Hence, the mechanical accumulation may another factor concentrating non-reproductive krill there. The frontal zone was considered to be favorable spawning ground for krill : not only because of the greater depth (which prevents krill embryos from being predated by benthic animals) and of the presence of warm Circumpolar Deep Water (which helps the development of the embryo) ; but also because of the higher chance of larvae's being transported to their nursery ground. Based on above mentioned factors, we further discussed why the change in spatial distribution of krill occurs from early to late summer.

The possibilities of natural regionisation of antarctic krill's geographic area with emphasis on fisheries regions distribution are considered on the base of consisting data of spatial structure of krill's geographic area. More then 43% of regions, where usually present concentrations of krill (this percent includes all recently acting fishery regions) lay inside of secondary fronts. These fronts are natural boundaries of supposed krill's stocks (subpopulations). Such position of regions of increased abundance of krill creates strong difficulties for determination of the membership crustacean to that or another stock on the basis of recent knowledges.
Problem may be solved, if new multidisciplinar surveys will be undertaken. These expeditions should get information on spatial composition of waters, ways of krill drift as well as on main biological characteristics of crustaceans. These surveys should cover rather large districts, which must include corresponding fishery regions as well as other regions of incresed abundance of krill and also regions of low abundance of krill. Changeability of situations (seasonal and annual) rises the necessarity to repeate these observations during several years, which is very expensive and impossible in reality. Information of observers from commercial trawlers as well as data from searching ships are a serious help in this respect for intermediate years beetween the seasons of wide scientific expeditional activity.

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.