Serious concern has been raised for the sustainability of Phocoena phocoena populations, since they are threatened by extensive by-catch in commercial fishing gear. Beacon-mode pingers emit displacement sounds continuously and have been seen to reduce by-catch in fishery trials, which have led to mandatory use in several countries. The continuous sound source may however cause excessive noise pollution, habituation in the long term and exclusion from important habitats. This study assessed the behavioural reaction of wild P. phocoena to the alternative AQ626 Interactive Pinger, which always emits alerting sounds to stimulate echolocation, but only emits displacement sounds in active state when triggered by sonar. It was compared to the beacon-mode AQUAmark 100TM pinger in a simulated fishery situation. The results showed a clear, short-term, displacement effect in the dive after the one of the first trig, with a quick return to pre-trig behaviour and without exclusion from the area. The most important effect of displacement sounds from either pinger might not be to displace animals, since it did not stop the animals from passing through the array of pingers, but to increase their awareness of the presence and location of nets. In conclusion, since the AQUAmark 100TM pinger is known to reduce by-catch, in addition to transmitting much less sound, the interactive pinger should be considered a possible mitigation alternative to the beacon-mode pinger.
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Last updated: 04/28/06