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.