Assessment of fishing gear impact and performance using sidescan sonar technology

The increased sensibility of the International scientific community toward the exploitation of fishery resources, promoted the development of new technologies to study the behaviour and the impact of fishing gears on seabed. In the last ten years the physical disturbances caused by trawling has been widely investigated by using the sidescan sonar technology. In the Mediterranean, changes to marine habitats that are caused by fishing are most pronounced in otter trawls, Rapido and hydraulic dredge fisheries. Sidescan sonar technology permitted to identify these fishing gears impact. Hydraulic dredges and Rapido trawls are basically similar in their seafloor impact by flattening and ploughing seabed features. While the effects of otter trawling varies greatly depending on the amount of gear contact with the bottom, together with the depth, nature of the seabed, and the strength of the currents or tide. Generally otterboards imprint distinct tracks on the seabed, ploughing a groove which can vary from a few cm up to 30 cm deep. Also the present work suggests a further step in using this technology, by analyzing in real time the behaviour, the geometry and the performance of different fishing gears in addition to qualiquantitative evaluation of their impact on the seafloor.