WG-EMM-95

In fisheries acoustics, the standard sphere method of echosounder calibration is most commonly used (Johannesson and Mitson, 1983; Simmonds et al., 1984). To investigate the uncertainty in the method, a series of experiments were conducted in a deep tank (Demer and Hewitt, 1993). Results indicated that variations in pulse length (0.1 and 0.3 ms), water temperature (0.5 to 5.5 C), and choice of Read More
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Water flows in harvestable areas for Antarctic krill (Euphausia superba) on the continental slope and shelf of the South Shetland Islands were examined based on drifting buoy data. Convergent complex eddies were observed in harvestable areas on the shelf, while shear current was observed in those on the slope. Large-scale movements of the buoys suggest krill flux from the South Shetlands into Read More
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The analysis of twenty nine stomach contents collected in a colony close to Pirie Peninsula, South Orkney Islands, from 2 January to 18 February 1995, showed that fish were by far the main prey of the blue-eyed shag Phalacrocorax atriceps, followed by octopods, decapods and gammarids. Notothenia coriiceps constituted the bulk of the diet; however, its importance decreased by the end of the Read More
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The diet of lactating female Antarctic fur seals Arctocephalus gazella at South Georgia was investigated during the pup rearing period (January - March) of 1991-1994. Antarctic Krill Euphausia superba was the main prey item, occurring in 88% of all scats (n=497), whereas fish occurred in 47% and squid in 5%. There was considerable intra and inter-annual variation in the characteristics of Read More
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The krill-predators model is generalised by splitting post-first-year animals into adults and sub-adults, with different survival rates for these two groups. Broadly speaking, the sub-adult survival rate can be adjusted to ensure that the modelled predator population reflects observed growth rates, thus solving problems of lack of self-sustainability encountered in earlier model analyses. This Read More
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The Scientific Committee has requested advice on the feasibility of conducting a synoptic survey of krill biomass in Statistical Area 48. Example calculations are presented for estimating the amount of survey effort required to achieve a target level of precision using a stratified random sample design and results from the FIBEX and AMLR surveys. These calculations suggest that approximately 1 Read More
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Krill sampling was carried out onboard RV ‘Polarstem’ from January 25 to March 11, 1994 south of 66°S, between 68°W and 120°W. Krill Euphausia superba abundance and biomass was in the lower range of values generally found in the Antarctic Peninsula and Elephant Island region. A distinct spatial separation for size groups was observed for krill, with small size groups being more abundant in the Read More
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The seventh Antarctic research cruise by the R/V Kaiyo Maru of the Japanese Fisheries Agency was conducted in the southwest of the Scotia Sea, especially in the vicinity of the South Shetland Islands from December 1994 to February 1995. The main objective of the seventh research was an oceanographic and ecological survey in relation to the distribution and abundance of the Antarctic krill ( Read More
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One hundred and thirty nine stomach contents of the blue-eyed shag Phalacrocorax atriceps were sampled at Nelson Island, Antarctica, between 1 December 1994 and 2 February 1995. Fish were by far the main prey, followed by octopods, gammarids, euphausiids and polychaetes. Notothenia coriiceps, predominated in frequency (56%) and in mass (55%), whereas Harpagifer antarcticus was the most Read More
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The climate of tile Western Antarctic Peninsula (WAP) region is distinguished by large seasonal and interannual variability and by the occurrence of seasonal sea ice which changes the ocean-atmosphere interface, affects tile surface albedo, and modifies the annual temperature cycle. Air temperature records for several peninsula stations have been examined, and the annual progression of surface Read More
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Design of sondes for in situ measurement of zooplankton or other scatterers requires choosing among alternative transducer geometries. This contribution addresses the problem of choosing between cylindrical and circular piston transducers by comparing the performance of the two according to the principle that the acoustically active areas be equal. Computations are performed with the actual Read More
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A method is put forward which estimates the proportions by which the annual consumption of krill is split between predator species. This method uses data on the length distribution of krill from predator stomachs. The proportions estimated depend, through the krill yield model, on the schedule of krill natural mortality at age. In principle, such a method would allow inferences about this Read More
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Studied were four primary sources of uncertainty in krill density estimates from acoustic surveys. The variance in system calibration with a standard sphere was evaluated in relation to sphere material and diameter, water temperature, and pulse length (Demer and Hewitt, 1992). Calibration bias was investigated by comparing the theoretical and actual target strength (TS) values of four Read More
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In connection with future calculation of volume of krill immigration/emigration (flux) in the choosen polygones, the proves of active long-distance migrations of krill are considered. These proves are not undoubted. The most difficult problem, which nevertheless should determine the results of calculations, is the valuation of krill retention time. To make it more correct and natural it is Read More
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This paper summarizes Japanese krill catch data during austral summer in 1993/94 season. Main fishing grounds were persistently formed in the north of Livingston Island throughout the season, and the west of Elephant Island from April to May. CPUEs showed the highest values at the height of summer (early February - early March) in the north of Livingston Island, and April at the west of Read More
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A comparative analysis was carried out on stomach contents and pellets (=regurgitated cast) of the blue-eyed shag or imperial cormorant Phalacrocorax atriceps collected throughout the breeding season at Nelson Island, South Shetland Islands. This allowed to estimate correction factors necessary for the quantification of fish represented in pellets. These factors were obtained for Notothenia Read More
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The potential of multi-frequency acoustic technology for quantifying fish and plankton is widely recognized. At a U.S. GLOBEC workshop in 1991, one of the considered problems was measuring macrozooplankton and micronekton. It was concluded that in order to survey animals in the size range 0.5-5 cm, it would be expedient to use at least three and perhaps as many as 8-10 frequencies in the range Read More
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Anomalies detected in the firmware of a Simrad EK500 echo-sounder are described so that users are aware of potential problems and how to solve them.

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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A proposal to monitor changes in coastal fish populations is presented in this document. The methodology considered is based in the analysis of regurgitated pellets of the blue-eyed shag Phalacrocorax atriceps. The fundaments of the proposal as well as the methods tested and the steps followed are also provided.

A population dynamics model for Adelie penguins is developed which takes account of the factors of lower adult survival rates in the year of first breeding, and the possibility that such breeding may be deferred one year if conditions are poor. A Bayesian approach for estimation of the model parameters is put forward; its estimation performance (including robustness to certain mis- Read More
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Dual frequency (38 and 120 kHz) acoustic surveys were carried out in two regions along the northern coast of South Georgia from RRS lames Clark Ross during January 1994. Difference in signal strength between the two frequencies (δMVBS = MVBS 120 kHz - MVBS 38 kHz) was used to discriminate krill from other acoustic targets. A generic target strength to weight relationship was used to derive Read More
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An attempt was made to develop simple, inexpensive, rapid means of determining body composition in Antarctic fur seals (Arctocephalus gazella). Measurements of total body water (TBW) and total body lipid (TBL), obtained by hydrogen isotope dilution, were compared to the results of bioelectrical impedance analysis (BIA) and morphometric indices of body condition in 52 adult females. TBW was Read More
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This paper demonstrated the relationship between sea-level air pressure gradients in Drake Passage and krill recruitment variabiIlty. Years of high pressure gradients coincided with the years of good krill recruitment, and vice versa.

The diet of Cape petrel was investigated on Mossman Hills, Laurie Island, South Orkney Islands in January-February 1995. Twenty stomach contents were sampled by a water offloading method, during late incubation and chick-rearing period. The analysis of the samples showed that Euphausiids were by far the main prey. Antarctic krill Euphausia superba constituted the bulk of the diet, predominated Read More
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This paper describes in detail a method for obtaining food samples from Pygoscelid penguins and some suggested modifications to CEMP Standard Method A8. It proposes a new method for draining the water from samples, an extension of the sampling period to include the guard phase, and that birds found to be empty of food be included in the data set if they are bona fide breeders. It also suggests Read More
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A method is described for calculating indices of sea ice distribution from digital data distributed by the National Snow and Ice Data Centre, Colorado, USA. Data consist of an image of the Antarctic, made up of 312x332 pixels, each having a dimension of 25x25km, for every day in the year. Primary data of the distance of sea ice from CEMP sites, the northerly position of the sea ice edge, and Read More
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The survey design for an integrated biological/physical survey of Division 58.4.1 during January - March 1996 is presented in this paper. Key measurements to be taken during this survey include hydroacoustic determinations of krill distribution and abundance and physical oceanographic sampling along 18 regularly spaced transects from the Antarctic coastline to a distance of 180 n miles. The Read More
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Dual frequency (38 and 120 kHz) acoustic surveys of shelf-break regions in the vicinity of Willis Islands, South Georgia and Coronation Island, South Orkneys, both in the Atlantic sector of the Southern Ocean, were carried out from RRS lames Clark Ross during January 1994. Difference in signal strength between the two frequencies (δMVBS = MVBS 120 kHz - MVBS 38 kHz) was used to partition Read More
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Distribution and biomass of salps and Antarctic krill (Euphausia superba) were investigated near the South Shetland Islands during austral summer 1990-1991. Salp biomass ranged between 0 and 556 mgC•m-3 and was greatest at a station in the Bransfield Strait in late December 1990. Salp biomass was lower than that of E. superba. Two species of salps; Salpa thompsoni and Ihlea racovitzai were Read More
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Data from the acoustic surveys of MV SA "Aghulas" and FRV "Walter Herwig", and the 1981 RRS "John Biscoe" South Georgia acoustic survey were analyzed by geostatistical methods. Estimates of mean density (g m-2) of krill and their variances are compared with published results (Trathan et al., 1993 and Murphy et al., 1991) from statistical analyses based on random sampling theory. A further high Read More
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The pattern of prey distribution can profoundly affect the foraging behavior and success of a predator. In pelagic marine ecosystems, where prey is often patchily distributed, predators must be able to adapt quickly to changes in the spatial patterning of prey. Antarctic fur seals feed primarily on krill, which is patchily distributed. When combined with information about swimming speed on the Read More
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Shipboard tracking study of breeding chinstrap penguins (Pygoscelis antarctica) and Antarctic fur seals (Arctocephalus gazella ) at Seal Island were conducted to identify and evaluate their foraging areas in late December 1994 (Leg I) and late January 1995 (Leg II). Leg I and Leg II corresponded to the incubation and guard period, respectively, for chinstrap penguins ; penguins were divided Read More
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Observations on abundance of by-catch fishes were made during the austral summer months of 1995 (from 30 January to 18 February) on board F/V Niitaka Maru to the north of the South Shetland Islands. Among 78 hauls examined, a total of 97 specimens of fishes belonging to five species, Electrona antarctica, Electrona carlsbergi, Protomyctophum tenisoni, Krefftichthys anderssoni and Notolepis Read More
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Historical hydrographic data from Bransfield Strait and the region west of the Antarctic Peninsula were analyzed to provide a description of water mass distributions and circulation patterns. Circumpolar Deep Water (CDW), which is characterized by temperatures above 1.0°C, salinities of 34.6 to 34.73 and oxygen values below 4.5 ml 1-1, is the most prominent water mass in this region, is found Read More
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Consistent gender differences in foraging trip durations, feeding localities and diet of breeding Adelie penguins were demonstrated at two widely separated locations over a number of years. Female penguins tended to make longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill, especially when chicks were small. Males tended instead to Read More
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One hundred and seventy three regurgitated casts of the blue-eyed shag or imperial cormorant Phalacrocorax atriceps were collected in a colony at Half-moon Island, South Shetland Islands, by weekly sampling throughout the breeding season from December 1993 to February 1994. Demersal-benthic fish were the main prey (91% in number) followed by mollusks and polychaetes. Six fish species were Read More
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During sustained bouts of diving, predators like fur seals may adjust the time they spend diving to maximise the time they can spend foraging and minimise the time spent at the surface between dives. To examine this, swimming speeds and the time allocated to different parts of the dive cycle were measured in 10 adult female Antarctic fur seals (Arctocephalus gazella) while they were foraging Read More
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Feeding behavior of Antarctic krill (Euphausia superba) on salps was observed through onboard experiments during 1994/95 Kaiyo Maru Antarctic Ocean research cruise. Feeding rate was more than 1 salp/krill/day. Among 4 items of ethanol extracts; salps, phytoplankton, krill, and polychaets, krill preferred salps best. This evidence implies that the substances extracted from salps were most Read More
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Experiments on estimation of krill transport by a current and its distribution characteristics variability were carried out within a local ground of Subarea 48.3 in the fleet operation area. It is shown that krill transport by wat4er flow across the fishing ground results in variation of fished krill aggregations distribution, and thus, in unstable indices of fishing vessels activity. During Read More
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During the Italian Antarctic Expeditions to the Ross Sea, in the years 1989 - 1994, using the 38 and 120 kHz BioSonics dual-beam hydroacoustic system, numerous swarms of krill Euphausia superba Dana were registered . Analysis of their physical parameters was carried out. It is known that insects appear to disperse according to a reaction diffusion model with a constant diffusion coefficient ( Read More
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Between year variability of krill year class success and recruitment during the 1977-1994 period are described based on data from German expeditions and U.S. Antarctic Marine Living Resources Program cruises in the Elephant Island area. The recruitment index (R1), based on the relative abundance of the 1 + age class, varies substantially between years, whereas it is quite similar between Read More
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A total of 45 pellets from the blue-eyed shag Phalacrocorax atriceps were collected in January 1994 at Duthoit Point, Nelson Island, South Shetland Islands. The analysis showed fish as the main prey, followed by octopods, polychaetes and gastropods. Notothenia coriiceps formed the bulk of the diet, but Harpagijer antarcticus was the most frequent and important fish in number. The prey Read More
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1. This study examined the costs of reproduction in terms of future survival and reproduction in female Antarctic fur seals from Bird Island, South Georgia. It used mark-recapture data from 11 consecutive years, including 3 years when several indices showed that food availability was well below average.
2. Population age structures were used, in conjuction with the measured age-specific Read More
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On the ground of materials collected by biologists-observers from October 1989 to June 1990 near the South Orkney Islands the growth of males and females are characterized according to size groups, distinguished using the probability paper. Seven size groups both for males and females were distiguished. The growth period for the males continued from October to April, and from October to Read More
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Interrelations between environmental variables, and between those variables and krill CPUE are discussed. Some reliable relationships is revealed. Based on those of krill abundance interannual fluctuations relationship hypothesis is formulated.

Based on a data set sampled during November/December 1994 in the Elephant Island Plateau Region by RV POLARSTERN, a water mass analysis is performed which reveals the approximate location of the Weddell-Scotia Confluence. Vertical distribution of oceanographic parameters temperature, salinity and density is discussed. Geopotential anomaly charts, referenced to different pressure levels outline Read More
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Detection of climate-induced change in marine ecosystems requires a knowledge of the underlying variability of the environment. This paper uses a range of datasets to investigate the interannual variability in Southern Ocean sea-ice dynamics. We present the first analysis of a series of fast-ice duration data from Signy Island, which we have cross-calibrated and combined with an earlier series Read More
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