WG-KRILL-93

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 Read More
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Data collected during the krill target strength experiment [J. Acoust. Soc. Am. 87, 16-24( 1990)] are examined in the light of a recent zooplankton scattering model where the elongatedanimals are modeled as deformed finite cylinders [J. Acoust. Soc. Am. 86, 691-705 (1989)].Exercise of the model under assumption of an orientation distribution allows absolutepredictions of target strength to be Read More
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The competition between Japanese krill fishery and penguins during their breeding season (December-March) in the South Shetland Islands (Subarea 48.1) was assessed based on available information on fishery, penguins and krill biomass. The catch is very low in December followed by roughly equivalent amount (3,000-10,000 t/10-day) for the following three months, with its increased fishing Read More
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Krill stock composition and distribution patterns in the vicinity of Elephant Island during austral summer 1991/92 and 1992/93 are described and compared with information from previous years. The general distribution of krill length and maturity classes conformed to previous descriptions and appears to be a recurring and predictable aspect of the krill stocks in the Antarctic Peninsula region Read More
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The distribution of krill catches in relation to land-based predator colonies, calculated from CCAMLR fine-scale data, is shown for Subareas 48.1 and 48.2. The pattern of catches in 1992 is similar to that seen for other years, with 70% of the total catch from Subarea 48.1 being taken within 100 km of colonies and between the months of December to March inclusive (the ‘critical period-distance Read More
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A maximum likelihood method is developed for the decomposition of krill density at length data into the proportion of recruits in population sampled in a net haul survey. Preliminary results from a series of 5 net haul surveys in the South Atlantic and the Indian Ocean sectors of the Southern Ocean give a mean recruitment rate for one year old krill of 0.339 with a standard deviation of 0.100 Read More
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A method is developed for using observed values of the mean proportion of recruits and its variance to model recruitment in a krill population in terms of numbers of recruits. The method includes the calculation of natural mortality and other parameters consistent with the observed proportional recruitment parameters. A procedure is given for generating families of recruitment functions which Read More
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A simple deterministic model is described which models the behaviour of the krill fishery in Subarea 48.1 and estimates the effort applied and the catch of krill in fine-scale squares. Parameters for the model are calculated from data reported to CCAMLR by Chile over the period 1989 to 1992. The distribution of catches predicted by the model, which is restricted to the months December to March Read More
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Food habits of the southern baleen whales were reviewed being based on the published and unpublished data since 1946. Past geographical distributions of the krill in the whales stomach revealed that the frequency occurrence by krill size showed that the large krill(>50mm) occurs more frequently in the whaling Areas II and III, then the size comes medium (40-50mm) in the Areas IV and V, and Read More
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Distribution and abundance of salps were studied near the South Shetland Islands during summer 1990/1991. Total salp biomass ranged between 0.1 and 2021.3 mg WW∙m-3 and was nearly equal to krill biomass in the area. Two species; Salpa thompsoni and Ihlea racovitzai were found, and the former was dominant. Horizontal distribution of salps and krill did not overlap. Krill occurred abundantly at Read More
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Biogenic silica (BSi), lithogenic silica (LSi), particulate organic carbon (POC) and nitrogen (PON), and chlorophyll a (Chl a) were measured in the surface waters (

A numerical model is being developed for assessment of Euphausia superba in Antarctic Ocean, which consists of:
(1)calculation of three dimensional current field using CCSR version (developed by Dr. Yamanaka of Center of Climate System Research, University of Tokyo) of the three dimensional primitive equation for the ocean circulation developed originally at the GFDL, Princeton, NJ, Read More
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Data from the Eduardo L Holmberg FIBEX survey have been re-examined for incorporation into the BIOMASS Database in the approved standardised format. The results indicate the krill were concentrated to the western end of the South Orkney Islands. Density values are consistent with those from other FIBEX surveys.

A theoretical prolate spheroid liquid model is applied to predict the target strength (TS) of krill. Scattering patterns are shown to demonstrate orientation dependence of krill TS. Length-to- wavelength ratio (L/λ) dependencies of reduced (normalized by body length squared) target strength are shown for some orientation distributions. The results can explain well-organized experimental Read More
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This document submits the basic information on the hydrographic flux in Statistical Area 58. Those are surface geostrophic flow in the whole of Statistical Area 58, and vertical distributions of geostrophic flow along 37° E, 75° E,114° E and 155° E.

Aim of this document is to supply a short information of chlorophyll distribution patterns around the South Shetland Islands in the Antarctic survey of R/V the Kaiyo Maru from 13 December 1990 to 11 January 1991 (Leg I) and from 16 January to 11 February 1991 (Leg II). In the north of Livingston Island, high chlorophyll a concentration and low POC/chlorophyll a ratio in Leg II and low Read More
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Acoustic methods appear to be the best way to estimate Antarctic krill abundance directly. Information on body orientation, however, is needed to obtain reliable krill acoustic target strength (TS) values, since TS varies with body orientation. Krill body orientation was measured in an aquarium aboard the R. V. Kaiyo Maru. Average body orientation was 45.6° (SD = 19.6°, N= 67), which was Read More
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This paper summaries Japanese krill catch data during austral summer in 1991/92 season. A main fishing ground was persistently formed north of the Livingston island. CPUEs show the highest values at the height of summer (late January - late March). Krill with modal lengths of 41-45 mm were dominant in catches, ca. 5mm smaller than those for the previous season.

During 1979 to 1991, relationship between the size of Antarctic krill and the extent of the sea ice in the sea area around the South Shetland Islands are described. Mean size of krill near the coastal zone appeared to be small in summer season just after a strong ice extent had occurred. This implies that strong recruitment of small size krill had occurred just after the season with the strong Read More
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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 Read More
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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, Read More
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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 Read More
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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 Read More
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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 Read More
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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 Read More
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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- Read More
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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 Read More
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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 Read More
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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 Read More
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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 Read More
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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 Read More
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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 Read More
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Data from several summer surveys to the Antarctic Peninsula region were analysed to calculate length and age at maturity for the Antarctic krill Euphausia superba. L50 values of 34.62 to 35.90 mm for female krill are the best estimates for the high spawning season. Males attain sexual maturity later at a length between L50 = 43.33 and 43.79 mm. Length at maturity, and length at first spawning Read More
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The results of Butterworth et al. (1992) relating potential krill yield to a pre-exploitation survey estimate of kril1 biomass are extended to incorporate most of the amendments specified by the Third and Fourth Meetings 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 Read More
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An initial attempt is made to develop the model1ing framework suggested by the Joint Meeting of the CCAMLR's WG-Kril1 and WG-CEMP in 1992 to address this issue. First. estimates are made of the parameters of predator survival rates as functions of krill abundance, by considering a krill dynamics model incorporating recruitment fluctuations together with information on adult survival and Read More
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Data on the size and age composition of Euphausia superba were collected in the Cooperation and Cosmonaut Seas from 1985 to 1990.
The coefficients of instantaneous natural mortality of E.superba in the Indian sector of the Southern Ocean were calculated according to Alverson-Carney’s (1975), Richter-Efanov’s (1977) and Beverton-Holt’s (1958) methods. Values varyed from 0.72 to 0.87, from Read More
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The materials on Euphausia superba biological state and size composition in the Indian Antarctic seas for the period from 1985 to 1990 are analyzed to form an opinion about its growth, life duration, as well as about the interannual variability in the above parameters.
According to our data, duration of E.superba life cycle somewhat exceeds 5 years in the Sea of Cosmonauts and 6 years in Read More
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The diving behavior of 7 chinstrap penguins (Pygoscelis antarctica) (N=12,171 dives) was measured concurrently with a hydroacoustic assessment of the vertical distribution and abundance of their primary prey, krill (Euphausia superba) in the vicinity of Seal Island, South Shetland Islands, Antarctica between January 19 and March 10 1992. Krill was found to show a distinct diel migration Read More
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The diel vertical migration of Antarctic krill (Euphausia superba) can greatly bias the results of qualitative and quantitative hydroacoustic surveys which are conducted with a down-looking sonar and independent of the time of day. To demonstrate and quantify these negative biases on both the estimates of biomass distribution and abundance, a time-depth-density analysis was performed. Data for Read More
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Acoustic estimates of krill biomass in the vicinity of Elephant Island for the years 1981-1993 (with the exception of 1982 and 1986) are presented. Estimates for 1981-1991 are based on previous reports adjusted for the recently proposed definition of krill target strength. Biomass estimates range from 81 xl03 t (March/April 1985) to 4,880 xl03 t (January 1993) and areal biomass densities range Read More
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Acoustic surveys are the most powerful tool of krill abundance estimation and distribution mapping. The International Community needs to prepare standard requirements and procedures for acoustic instrumentations to be used, as well as for survey design, data acquisition, processing, storing and analysis. In the paper possibilities and approaches to preparation of recommendations for acoustic Read More
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During the 6th Antarctic Expedition of R/V Kaiyo Maru (1990/1991), observations on the occurrence and abundance of fishes in a total of 102 pelagic hauls for the Antarctic krill were made.
Of the 102 net hauls, a total of 104 fishes belonging to 4 families and 16 species were captured in 25 tows. Juvenile Lepidonotothen larseni was the most abundant (46 individuals; 44.2% in number) and Read More
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Observations on abundance of by-catch fishes were made during the austral winter months of 1992 (from July 9 to August 3) on board F/V No.3 and No.5 Chiyo Maru in the vicinity of the South Georgia Island. Among 74 net hauls examined, a total of 66 specimens of fishes belonging to 3 species were found in 20 trawl catches.
Among by-catch fishes, juvenile Lepidonotothen larseni was the most Read More
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