Haddock avoidance reactions during trawling

Fish reaction to the whole trawling operation was studied using a stationary echo sounder-system observing the fish in front of the vessel and during trawl passage. Strong avoidance reactions were observed on haddock, with both horizontal and vertical movements of the fish. The observations indicate that the fish density available for the bottom trawl at shallow depths may be significantly higher than estimated by the echo integration system on board the trawling vessel, and that vessel avoidance may be an important trawl selection factor