ARIEL DID HANDBOOK
The DiD (Dolphin interactive Deterrent) is an electronic equipment able to keep the dolphins away from fishing nets, thanks to an efficient technique of interaction with their echolocalization system (sonar). Tested devices were STM Products S.r.l. (http://www.stm-products.com/prodotti/fishing-technology/dissuasori-per-delfini-green/did01~54.html). The use of the DiD 01 avoids most of the incidental captures of dolphins and protects the capture and fishing nets from predation by mammals, therefore it protects also the profit of the fishing industry. The device has a broadband transducer able to detect the presence of marine mammals in the surrounding area and to react by emitting variable ultrasounds in order to disturb their echo-localisation system and therefore to induct them to move somewhere else. The DiD is the interactive evolution of the standard DDD 03 models. It produces the ultrasounds only when it detects the presence of the dolphins in the area, by means of its “hearing” circuitry, that is activated by the “clicks” emitted by the mammals. It is powered by internal (sealed) rechargeable batteries and generates an acoustic signal in case of insufficient charge. The advantages of this model in comparison with the DDDs are the reduction of the possibility that dolphins become accustomed to the signals, the increased duration of the battery charge and the reduction of the acoustic pollutio. The level of the DiD emissions doesn’t produce any harm to mammals or
fish; these last are insensitive to the frequencies emitted.