Longline depredation and bycatch
I've also examined echolcation performance of false killer whales in the presence of acoustic deterent devices. These devices were designed to be associated with longlines and thus deter false killer whales from depredating, and occasionally becoming hooked on, the longline.
False killer whale (Pseudorca crassidens) echolocation and acoustic disruption: Implications for long-line bycatch and depredation
False killer whales (Pseudorca crassidens; Owen, 1846) depredate fish caught by the North Pacific pelagic long-line fishery resulting in loss of target species catch and the whales themselves becoming bycaught. This incidental take of false killer whales exceeds sustainable levels. In an effort to address a potential solution to reducing this depredation and bycatch we tested an acoustic device designed to deter false killer whales from approaching long-lines by reducing the whales’ echolocation performance capabilities. The device produced a series of complex, broadband signals (1-250 kHz) at high intensity levels (up to 182 dB). In the experiment, a trained false killer whale was asked to detect a target in the presence or absence of the acoustic device. Baseline performance capabilities were 95% correct responses. Initially, the device reduced the whale’s echolocation performance to chance levels. However, subsequent sessions demonstrated improvement in echolocation performance up to 85%. This improvement was likely a result of behaviorally adapting to the task and a decrease in the source level of the echolocation “disruptor.” The results underscore the challenges in using acoustic devices to reduce depredation and bycatch, and demonstrate the need for concern regarding anthropogenic noise levels and effects on odontocete echolocation capabilities.
This is a joint project with Institution Number One, College Number Two, Organization Number Three, and Corporation Number Four.