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    Investigations of krill transport factors in the local areas in the Scotia Sea: variability of krill distribution in the fishing grounds under the transport impact

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    Document Number:
    WG-EMM-07/17
    Author(s):
    S.M. Kasatkina and V.N. Shnar (Russia)
    Agenda Item(s)
    Abstract

    The authors look «inside» SSMU by the example of SOW (South Orkney West) and SGW (South Georgia West), analysing variability of krill transport and distribution characteristics in the local areas of these SSMUs. The data of the Russian repeated acoustic survey accompanied by trawl and CTD samples form the basis of this work. It is shown that the multiple replacements of the water masses in each study areas were accompanied with pulsatory pattern of krill transport, i.e. krill transported across polygon boundaries by non-uniform portions. Here not only the pulsatory pattern of the biomass value (in our case, CV biomass=57%) is important, but also the observed changes in krill aggregation patterns forming the transported biomass portions (in our case, CV swarms/mile 2 =63%). Therefore, krill biomass portions with different commercial importance were transported into the fishing grounds. The latter has been confirmed by the correspondent dynamic of the actual operational statistics of fishing fleet. The authors come to a determination that the development of krill stocks management procedures requires consideration of the temporal and spatial changes of krill transport factors in relation to dynamic of krill distribution indices and trawlers operation indices in various areas of the Scotia Sea. Simulation of such complex processes in ecosystem models (KPFM 2, SMOM, EPOC), developed for testing options of krill precautionary catch allocation among SSMUs, is possible only on the basis of the actual data describing annual and seasonal variability of krill biomass and aggregation characteristic distribution patterns in SSMUs under the impact of transport processes. Otherwise, the testing results will be insufficiently substantiated for the decision making.

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