WG-FSA-93

In an investigation of the age structure of a population of Notothenia coriiceps Richardson at the South Orkney Islands, Antarctica, the microstructure of otoliths was examined. Progress is reported on a method used for processing large numbers of otoliths using a scanning electron microscope (SEM). Compared with previous SEM techniques, which normally prepare otoliths individually for viewing Read More
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The paper presents calculations of water flow velocity through the codend under the assumption that the flow is uniform and equal on its entire surface. The calculations were made for different ratios of cod end length to its diameter, mesh bar length to mesh bar diameter, and for various mesh opening coefficients. The results obtained were analysed with regard to the impact of flow velocity Read More
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The Antarctic fish fauna is relatively impoverished with fewer than 300 species recorded from the whole Southern Ocean. Demersal forms predominate but many of these have extended early life histories as pelagic larval and juvenile phases. Only 30 larval stages of the 103 fish species occurring at South Georgia have been identified but these represent all of the dominant and economically Read More
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Discussed in this paper is an investigation on juvenile antarctic fish caught during krill fishing by the BAT GrigOly Kovtun in the region of the South Georgia Islands during the period May-June 1992.
Two species were predominant in the by-catches: Champsocephalus gunnari and Nototheniops larseni. The frequency of occurrence of juvenile fish was 18.2% when considering all krill tows and Read More
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To validate the timing of annuli in otoliths of immature Notothenia coriiceps Richardson. a time-series of samples were taken over a complete year. Light and scanning electron microscopy (SEM) techniques were used to examine the structure of sectioned otoliths. Six growth regions were identified in the otolith sections and micro-increments were also evident. The timing of growth and annual Read More
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A method is developed for calculating asymptotic confidence intervals for trawl surveys using the swept area method, using likelihood ratios from Aitchison's delta distribution. Simulation tests of the method show that unbiassed estimates of the density and biomass can be obtained and that the estimated confidence intervals have close to the nominal coverage probability. Performance Read More
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Analysis and synthesis of results of Russian and foreign research into the trophic relationships of myctophids demonstrate that this group of mesopelagic fish plays a significant role in the community of marine organisms of the Southern Ocean. The trophic status of myctophids has been determined - they are zooplankton-eaters who consume a considerable amount of meso and macroplankton which Read More
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The Lepidonotothen squamifrons group has been described to be comprised of 3 species: L squamifrons (Günther, 1880). L kempi (Norman, 1937) and L macrophthalma (Norman, 1937). All 3 species closely resemble each other and morphological and meristic characters utilized to distinguish between species are overlapping. Enzyme electrophoresis of enzyme polymorph isms has been applied to specimens Read More
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An experimental management strategy is proposed for the Paralomis spinosissima fishery around South Georgia. The strategy is designed to answer specific, a priori questions about the population dynamics of P. spinosissima, and consists of three phases to be conducted over a period of two years/fishing seasons. Phase 1 occurs at the start of the first fishing season and is a "survey" regime Read More
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A revision of the calculation of total international catch at age of Champsocephalus gunnari over the period 1976/77 to 1990/91 is presented. This uses iterative application of two age length keys to obtain age distributions, according to a method described by Kimura and Chikuni (1987). It is proposed that the revised catch at age be used for future assessment of the C. gunnari fishery at Read More
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Samples of fish collected from 1983 to 1992 at Potter Cove, King George Island, South Shetland Islands, are used to study the decline in abundance previously reported fro fjord Notothenia rossii, in association with changes in the size and age structure of the juvenile population. Mean lengths increased in correlation with poor recruitment to inshore waters and sharply decreased as stronger Read More
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The Kerguelen fishery (trawlers and long-liners) of Dissostichus eleginoides is analyzed in the ligth of the knowledge of life cycle of the species. Catches reach a similar cumulative value that in South Georgia subarea (48-3). Fishing grounds and fishing methods have been separated and the tendancies from the LFD and an index of abundance compared.

Patagonian toothfish, Dissostichus eleginoides, spawn in July to September. Hatching is likely to occur in October/November. Scales do not start to form before the fish are 64-74 mm long. It is far from being resolved when the first 'winter ring' is formed. Available information suggests that the annulus may not be completed before spring. Length composition of fish <40 cm exhibited Read More
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On the basis of analyses and review of published data on the biology and distribution of Electrona carlsbergi, as well as on the hydrological patterns of the Southern Ocean - especially concerning the structure and spatial variation of the Antarctic Circumpolar Current (ACC) - this paper describes possible ways and means (mechanisms) by which this species carries out meridional migration in Read More
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Ovarian maturation in Notothenia coriiceps is known to include a period during which yolk deposition begins to take place. This 'adolescent' phase was thought originally to last for about one year. The results from a two year study at Signy Island indicate that this adolescent phase lasts for about four years. There is also some evidence to indicate that not all sexually mature fish spawn each Read More
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Four production models were fit to a time series of daily catch per unit effort (CPUE) data from the 1991/92 fishery for Paralomis spinosissima around South Georgia Island. The four models considered recruitment in different ways. Model 1 contained a linear recruitment function; Model 2 had constant recruitment; Model 3 contained a Beverton-Holt recruitment function, and Model 4 used a Ricker Read More
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The diet composition and feeding intensity of mackerel icefish ( Champsocephalus gunnari) around Shag Rocks and the mainland of South Georgia was analyzed from c. 8,700 stomachs collected in January/February 1985, January/February 1991 and January 1992. Main prey items were krill (Euphausia superba), the hyperiid Themisto gaudichaudii, mysids (primarily Antarctomysis maxima) and in 1985 also Read More
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