WG-KRILL-94

The parameters used to model gear selectivity and maturity at length in the SKDM were derived from data available at the CCAMLR Data Centre or in documents submitted to past meetings of the Scientific Committee. In the SKDM, if l50 for selectivity and maturity is to be sampled from a uniform distribution, and applied to a standard function width, then these should be
lr50 = U[30,39] wr Read More
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The method of simulating recruitment variability using observed ratios of 0 year krill to the total population is validated and tested. The method also links natural mortality to krill recruitment. Incorporation into the SKDM increases the variability of the krill population dynamics predicted by the model, although median escapement is similar to the previous formulation of the model.

In 1994 the group of above mentioned authors has completed the first stage of researches for creation of an imitation model of krill distribution and search in the Cooperation and Cosmonauts Seas (30–80°E). At this the following main problems were addressed: - Systematization of krill echograms (types of aggregations, their main characteristics), - Assessment of distribution of aggregations ( Read More
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Poland began krill fishing operations in the 1976/1977 season. It has been engaged in krill commercial fishery since the 1986/1987 season. Maximum catches, equalling 15.9 thous tonnes. were, attained in the 1992/1993 season. The report presents an analysis of Polish krill catches in the 1991/1992 and 1992/1993 seasons. CPUEs by month in individual subareas of the Atlantic sector of the Read More
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In-situ measurements of target strength (TS) were made of Antarctic zooplankton (Euphausia superba and Salpa thompsoni) at 120 kHz and 200 kHz. Concurrently, a two meter Isaacs-Kidd midwater trawl was used to sample the zooplankton populations and animal length-frequency data were recorded. The TS and length-frequency data were combined to corroborate theoretical scattering models for both Read More
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Target strengths (TS) of various zooplankton were measured at 200 kHz, 420 kHz and 1 MHz and the dependence of these data on animal volume versus cross-sectional area was explored The 420 kHz and I MHz data were collected with a dual-beam sonar system and the 200 kHz data with a split-beam system. Experiments were conducted with live, tethered individuals in an enclosure filled with filtered Read More
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Maps of krill (Euphausia superba) density derived from acoustic survey data and the distribution of fishing effort in the Chilean krill fishery indicate an area of high krill density wrapping around the northwestern end of Elephant Island during the austral summer of 1992. In this area, the distribution of catch-per-fishing-time and krill density (measured acoustically) show similar forms. Read More
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The reproductive state and size composition of Euphausia superba collected in the Indian sector of the Southern Ocean from 1985 to 1990 were analyzed to estimate its growth, life span and mortality rates. The duration of the life cycle of E.superba exceeded 5 years in the Cosmonaut Sea and 6 years in the Cooperation Sea. Assuming growth for only 180 days per year, growth rates ranged from 0. Read More
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Laboratory studies have shown that Antarctic krill Euphausia superba shrink if maintained in conditions of low food availability. Recent studies have also demonstrated that E. superba individuals may be shrinking in the field during winter. If krill shrink during the winter, conclusions reached by length-frequency analysis may be unreliable. In this study, the correlation between the body- Read More
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Hydroacoustic surveys of the abundance of krill (Euphausia superba) in the Prydz Bay region were undertaken in January/February 1991, February/March 1992 and January/February 1993. The surveys indicated some association of krill with the shelf break in the western part of the survey area and the centre of the Prydz Bay region but also found that the shelf break was in general not a region of Read More
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Between year variability of krill year class success and recruitment during the 1975-1994 period are described based on data from German expeditions and US AMLR cruises in the Elephant Island area. Recruitment indices based on the relative abundance of the 1+ year class during each year indicate good recruitment of the 1980/81, 1985/86, 1987/88 and 1990/91 year classes; exceedingly poor Read More
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Preliminary computations are carried out for the krill yield model of Butterworth et al. (1993), adjusted as requested by the fifth meeting of WG-KRILL. This involves modifying the input distributions for the lengths at recruitment and maturity, natural mortality and the extent of recruitment variability. Sensitivity tests are carried out to assess the consequences of avoidance of gravid Read More
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Earlier initial modelling attempts by the authors are extended to consider the situation where predator survival rates depend on other factors in addition to krill biomass. This is achieved by making the survival rates depend instead on krill "availability", where there is a random component in the relationship between krill biomass and availability. An examination of the consequences in the Read More
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Observations on abundance of by-catch fishes were made during the austral summer months of 1994 (from January 12 to February 18) on board F/V Niitaka Maru in the north of the South Shetland Islands. Among 99 net hauls examined, a total of 77 specimens of fishes belonging to 13 species were found in 25 trawl catches (Table 1).
Among by-catch fishes, juvenile Lepidonotothen larseni was the Read More
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On the processes to investigate a proper model for understanding the processes that govern the biochemical cycle in Antarctic Ocean, we made a research plan as follows: (1) to develop an OGCM (Ocean General Circulation Model) (2) to develop a one dimensional ecosystem model that can be applied to primary production in Antarctic Ocean (3) to develop an ecosystem model able to describe krill Read More
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This paper summaries Japanese krill catch data during austral summer in 1992/93 season. A main fishing ground was persistently formed north of the Livingston Island. CPUEs show the highest values at the height of summer (late February - late March).Krill with modal length of 41-45mm were dominant in catches, almost same as the previous season.

This document submits the basic information on the hydrographic flux in Statistical Area 88 of CCAMLR in the Pacific sector. Those are surface geostrophic flow in the whole of the Statistical Area 88 and vertical distributions of geostrophic velocity and temperature along 90°W, 120°W, 170°W and 175°E respectively.

In this present report the change of the Antarctic krill distribution pattern from December 1983 to January/February 1984 in the vicinity of Prydz Bay was analysed. The results showed the remarkable change of sex ratio and coefficient of fatness between the early summer and the midsummer. The waters indicating the high ratios of female krill with the high coefficient of fatness were considered Read More
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An acoustic survey at 38 and 120 kHz was carried out from RRS Discovery in the Bellingshausen Sea from 23 November to 7 December 1992 as part of the UK Joint Global Ocean Flux Study (JGOFS) Southern Ocean investigations (TuRNER and OWENS, 1995). A total of 285 targets were identified and described from the chart record of the echo sounder. Mean Volume Backscattering Strength data were Read More
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In 1994 Ukraine has recommenced krill fishing which was terminated in 1993. It is conducted by two vessels BAT GRIGORY KOVTUN and RKTS GENERAL PETROV. Scientific observer M. Speranskaya, YugNIRO scientist is on board the latter one.
The fishery and scientific information given in this paper is based on operative data. That is why some correction of these data is possible after the observer Read More
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Conditions for precise measurement of in situ fish target strength (TS) are empirically studied and two indexes are introduced for this purpose. One is the number of fish in the effective reverberation volume which contributes echo formation at a certain instant and the other is the percentage of the multiple echoes which is derived from a residual of the single echo extraction. With the Read More
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Publication:
Sawada, K., M. Furusawa and N.J. Williamson. 1993. Conditions for the precise measurement of fish target strength in situ. The Journal of Marine Acoustics Society of Japan, 20(2): 73-79. https://doi.org/10.3135/jmasj.20.73

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