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    On dispersion of different pelagic organisms, forming Antarctic backscattering in South Sandwich subarea during January–February 2000

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    S.M. Kasatkina and A.P. Malyshko (Russia)
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    In the paper these have been discussed the results of acoustic estimation of distribution nectonic organisms, non-krill zooplanctonic fraction and krill as detected my multi-frequency echosounder in 48.4 Subarea.
    It has been shown that myctophid fish species are dominated in nectonic fraction backscattering. Nectonic organism distributional pattern is evidently attributed, to a greater degree, to myctophid fish species.
    There have been obtained differences between spatial distribution of different groups of pelagic organisms. One can reveal, basing on the results of surveying , the influence of water mass type on distribution of different pelagic organisms groups that form antarctic backscattering layers as follows: krill predominatingly contributes to the antarctic pelagic community within proving ground locations occupied by the Weddell Sea waters and Frontal Zone of Weddell Gyral waters; myctophid fishes prevail in northern proving ground within the Antarctic Curcumpolar Current waters; zooplankton is distributed in the Weddell Sea waters. Though krill and zooplankton major biomasses are concentrated in upper 80-90m layer, high densities of myctophid fish are observed within the whole depth range of 0-350m. At the depth of more than 90m principle backscattering recorders can be pertained to myctophid fish species.
    A comparative analysis of mean stratum Sa values obtained for krill and myctophid fishes indicated that biomass of myctophid fish species could be considerable. The estimate of myctophid fish biomass which can be a part of alternative trophic chain in relation to krill is evidently of practical interest .