Henryk SENDŁAK
Academy of Agriculture, K. Królewicza 4, 71-550 Szczecin, Poland

Key words: fishery, trawling system, pelagic trawl, trawl drag, opening parameters.

Abstract.
Changes in the length of trawl warps bring about a change in the working parameters of the pelagic trawling system. In this paper, based upon model tests, the influence is discussed of the length of trawl warps upon the shape of the mouth and the drag of a modern design of a large-sized pelagic trawl used for catching scattered shoals of fish in the open ocean. The models were tested within the trawling speed range of 1.9-2.5 m/s with trawl warps 55, 80 and 120 m in length (550, 800 and 1,200 m in real scale, respectively). As we increase length from 55 to 120 m, there is an increase in horizontal opening by around 20%, and a decrease in vertical opening by around 15%. As a result of an increase in trawl door spread by around 25%, the penetration zone of the pelagic trawling system increases. Concurrently, there is an increase in the drag of the trawling system by around 12%.