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    Midwater trawl catchability regarding quantitative estimation of krill biomass using the method of trawling surveys on abundance

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    S.M. Kasatkina (USSR)
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    Midwater trawl catchability is variable depending both on fishing object behaviour and distributional pattern end trawl parameters. Data on trawl catchability distribution parameters and krill distributional pattern in the surveyed area enable to increase reliability of the biomass estimates.
    Comparative analysis for catchability of fishery midwater trawls and small research trawls, when Isaaks-Kidd trawl was taken as an example, proved the latters not to be suitable for krill biomass estimation using method of trawling surveys on abundance. Small research trawls were found to have high catchability variations in the surveyed ground and the biomass estimates were characterized by high relative error.
    Standard methods of trawling survey on krill abundance should be worked out. Optimum construction of midwater trawl can be selected on the base of mathematical modelling using models of the fishing trawl statistical theory and conducting hydroacoustic studies of trawl catchability properties. Selection of trawl construction should include studies on estimation of krill total exemption.