WG-KRILL-92

The results of Butterworth et al. (1991) relating potential krill yield to a pre-exploitation survey estimate of krill biomass are extended as specified by the Third Meeting of Working Group on Krill. The most important of these extensions is integration over the ranges of uncertainty for a number of the model parameters. Results are provided for the probability of spawning biomass falling Read More
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Interannual variations in krill quantative characteristics in the Sodruzhestva Sea area for the period from 1988 to 1990 are discussed in this paper. It has been established, that a considerable increase in the crustacea stock in 1990 was caused by good replenishment owing to the generations of 1986 and 1987 in the conditions of their weak expatriation in 1989–1990.

An observation program was carried out by a biologist-observer on board the krill fishing vessel More Sodruzhestva in April to August 1991 in Subareas 48.2 and 48.3. The program included observation of krill fishing operations, collection and processing of catch samples for analysing physiological status and size composition of krill and also for determining the level of by-catch of juvenile Read More
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Parameters of the Bertalanfy growth equation for 1928 and 1970–1976 were calculated on the base of summaryed data on Krill age groups singled out using method of Harding.Parameters obtained were used to calculate total Krill mortality using different methods applyed earlier only to the fish recources.
As a result of uncertainty in age groups determination were obtained wide ranging values Read More
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Investigations of diurnal changeability of size composition of E. superba was carried out during the working period of commercial trawler ‘Grigory Kovtun’ in the fishing area near the South Orkney Islands during March-June 1990. observations at 6 time stations were fulfilled. Every station consisted of series of catches by mean the usual commercial trawl (9-12 tows per every station). Read More
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Main outlines of E. superba material collection (sampling from commercial catches) and positions of samples examination are reviewed and described. These positions include mass-measuring of body length, examination of maturity stages composition (biological analysis), feeding activity observation and body weight determination. Periodicity of sampling and volume of samples for every position of Read More
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Empirical estimates for the target strength of krill are extracted from the literature. These are confined to measurements on aggregations of live euphausiids, which should avoid a frequent cause of bias in single-animal measurements, namely thresholding. Theoretical estimates for the target strength are derived from the deformed-cylinder scattering model assuming specific sets of physical and Read More
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Krill stock composition and distributional patterns in the vicinity of Elephant Island during austral summer 1988-1992 are described. Changes in both size and maturity composition over the five year period indicates strong recruitment from the 1987/88 and 1990/91 year classes and poor recruitment from the 1989/90 and 1990/91 year classes. Year class success may be related to the abundance of Read More
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Length-weight relationships for krill Euphausia superba are listed for ash-free dry weight, dry weight, and wet weight as well as relationships for other Antarctic euphausiid species. Information on sex and dominant maturity stages underlying the data are supported. The influence of seasonal changes in length-weight relationship parameters is discussed. Recommendations are given for the use of Read More
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CCAMLR Conservation Measure 32/X sets a 1.5 million metric ton precautionary catch limit on krill (Euphausia superba) in Statistical Area 48. The measure also asks the Scientific Committee to provide the Commission with advice on how precautionary limits could be applied to subareas or local areas. Nine alternative methods of determining subarea or local area krill catch limits are evaluated Read More
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This paper outlines the theory and procedures for calibrating an echo integration acoustic system with a standard sphere. It presents the results of an extensive calibration of a Simrad EK500 scientific echo sounder with a 120 kHz sprit-beam transducer in a refrigerated 10m deep tank. Calibration parameters are studied in relation to sphere material (WC and Cu), water temperature (0.5-5.5°C), Read More
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The distribution of krill catches in relation to predator colonies in Subareas 48.1 and 48.2 is shown. 74-90% of catches in Subarea 48.1 are taken within 100 km of predator colonies between December and March, and these are between 10 and 18% of the estimated total penguin consumption in this period. The pattern of fishing is very consistent in all years 1988-1991 in Subarea 48.1, but is more Read More
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Zones of 20 km width are defined around selected colonies of penguins distributed around the coasts of the South Shetland and South Orkney Islands. Krill catches in these zones are shown to have a consistent pattern in Subarea 48.1 but an unpredictable distribution in Subarea 48.2, probably as a result of more variable hydrographic conditions. About 50% of the catch in Subarea 48.1 from Read More
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The current subdivision of the CCAMLR Area is examined and some of the problems inherent in the system are outlined. A rationale for the further subdivision of Area 58 is developed and a scheme is suggested based on : available data on krill distribution patterns, oceanographic features and on fishery data.

Hydroacoustic surveys of the abundance of krill (Euphausia superba) in the Prydz Bay region were undertaken in January/February 1991 and February/March 1992.
The surveys indicated some association of krill with the shelf break in the western part of the survey area but also found that the shelf break was in general not a region of relatively high krill abundance. The mean surface density Read More
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The sixth Antarctic survey cruise of R/V Kaiyo Maru was carried out in waters around the Shouth Shetland Islands. where are known as the fishing grounds of krill, during the 1990-91 austral summer. In order to investigate seasonal changes in oceanic structure. two observations were put into operation In the same area after an interval of 40 days. The more characteristic change was clearly Read More
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Acoustic and net sampling surveys for krill were conducted in the krill fishing area north of the South Shetland Islands from 18 January to 3 February 1991. Distinct offshore-inshore heterogeneities in abundance and maturity of krill were observed. The survey region was divided into four zones; oceanic, slope frontal, neritic and nearshore zones. The mean density of krill was low in the Read More
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Shipboard tracking study for krill-eating predators (penguins and female fur seals) at Seal Island were conducted to identify and evaluate their foraging areas during early January 1990/91. Penguin foraging areas were formed in inshore region, where krill frequently occurred but higher density areas of krill (≥250g/m2) were rather limited. In contrast, fur sea! foraging areas were formed in Read More
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