Le répulsif à cétacés : performances acoustiques requises

Acoustic deterrent devices could be an appealing solution to tackle accidental cetacean by-catches in pelagic trawls or in fishing net gears. The bibliographical data on two species (Harbour porpoise and bottlenosed dolphin) have been analyzed in terms of audiogram, discomfort noise level that could lead to behavioural changes, sensory fatigue, and threshold for permanent hearing injuries. It is possible, on the basis of the above data, to characterize an efficient annoyance sound threshold which is not harmful to the species to be protected. Taking into account the properties of the sound waves propagation in the marine environment and according to the required range, the minimal amplitude of the repulsive sound to emit is proposed. Accordingly, the potentially efficient signals (frequency modulation and pulsed signals), with repulsive and echolocation masking effects are presented. These acoustic features, theoretically required for the need-adapted pick-up, are compared with the acoustic alarms (pingers) currently on the market and which are provided with low emission level that increases their autonomy. In conclusion, we can seek a new development and integration of a new generation repulsive device, including features that fit the previously described requirements.