Damage or removal of captured fish from fishing gear (depredation) can result in catch loss or a decrease in its economic value and often damages the fishing gear. Depredation by dolphin appears to be growing in frequency, geographic extent, and severity and is responsible for substantial economic losses. Because of this, the fishing industry is in urgent need of mitigation measures that can reduce the frequency and severity of such interactions (Cruz et al 2014).
In some fisheries, the use of alerting devices (deterrent pingers) have been successful in reducing dolphin depredation. However, in many cases the acoustic signals coming from such devices (<150dB) are low in power and after a period of time the dolphin become acclimatised to the low intensity noise and depredation recommences. In some instances, where deterrent pingers have been used to prevent depredation, the depredation observed when they return is much higher than was observed prior to using the deterrent pingers. The anti-depredation pinger is louder than standard deterrent pingers, producing a randomised unpredictable sound that startles dolphins when in close proximity to the net. A 100m spacing is recommended for maximum effect; this can be varied depending on fishing gear, region and dolphin species.