Analysis of Russia HAK-4M trawl catchabilities has been made in the paper. This trawl have been used when icefish bottom surveying. An analysis of total catchability and a differential one (that is catchability in relation to fish of different length) has been realized by models of probability statistical theory for fishing trawls. Influence of trawling speed, trawl configuration and distribution patterns of fish aggregations under consideration on trawl catchability has been shown. It has been demonstrated that the bottom trawl was not a measuring system. There have been discussed matters of improving trawl survey methodology related to the bottom trawl application as a measuring system.
Abstract:
Revision of icefish (С.gunnari) stock estimate in South Georgia Area was caused by elaboration of the following methodical aspects of trawl-acoustic survey: the processing method improvement for target strength estimates using in situ measurement data; the combination of trawl and acoustic surveys results for icefish biomass estimates .
We discus these methodical aspects and present the new icefish target strength estimated obtained from in situ measurement data by bootstrap-method and biomass estimates and its statistical characteristics. Major sources of uncertainties in icefish stock estimates and some ways of improvement of icefish stock estimates are shown too.
