Preliminary results from tests using a high-frequency sonar as trawl-sonde

Abstract

A high-frequency, short-range sonar is tested for trawl-geometry measurements on pelagic and bottom trawls. The sonar was operated on a standard, coaxial trawl sonde cable, and produced excellent images of the trawl opening and panels. Data showing non-ideal performance of the pelagic sampling-trawl at several depths and speeds, together with corrected geometry are presented. At short range, the position of fish entering the bottom trawl could be measured.