Fish reaction to trawling noise: The significance for trawl sampling

The reactions of fish during trawling were observed with a stationary echo sounder as a trawling vessel passed close to the transducer. Several strong, downward avoidance reactions of haddock (Melanogrammus aeglefinus ) were recorded. At depths greater than 100 m, however, the reaction pattern was weak and irregular. A comparative analysis of echo-integrator data at random bottom-trawl sampling sites indicates that fish avoidance occurs between the surface and 200-m depth, even before the vessel arrives. At greater depths, such pre-vessel avoidance reactions are not significant