FISHING TRAWL Russian patent published in 2002 - IPC

FIELD: large-sized trawls. SUBSTANCE: trawl has mouth part and enclosure with cables for connecting mouth part wings to otter boards, and telemetering instrument for controlling trawl parameters. Acoustic concentrator is attached to each trawl wing for rotation around its axis and has acoustic emitter, multiple program control device and acoustic emitter signal blocking device adjusted for blocking acoustic field within quadrant of the expanse of water faced to longitudinal axis of net trawl at an angle of 180 deg counted off from vertical plane. As a result, extended semicylindrical acoustic fish barrier fields are created in trawl advancement direction. These fields are periodically interrupted and changed as to their spectral structure after each pause and, thus, define at both sides extended soundless strip of expanse of water by planar surfaces well developed in vertical plane. Planar surfaces are oriented in parallel with related cables of net trawl so as to embrace related otter boards at their outer sides. Such geometric shape of acoustic fish barrier fields and periodicity of acoustic signal emission cause shoals of fish to be held and accumulated in soundless strip, as shoals of fish approach to net trawl in the course of advancement of trawl, due to narrowing of soundless strip with following catching of compacted fish mass by trawl net. Trawl is preliminarily set to optimal trawling horizon in accordance with trawl echo sounding device indications and setting is corrected on the base of indications of telemetering trawl control device. EFFECT: increased efficiency and enhanced reliability in operation. 2 dwg