Risso's dolphin depredation in the Azorean hand-jig squid fishery: assessing the impacts and evaluating effectiveness of acoustic deterrents

Published source details Cruz M.J., Jordao V.L., Pereira J.G., Santos R.S. & Silva M.A. (2014) Risso's dolphin depredation in the Azorean hand-jig squid fishery: assessing the impacts and evaluating effectiveness of acoustic deterrents. ICES Journal of Marine Science, 71, 2608-2620.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices on fishing vessels Action Link

Use acoustic devices on fishing vessels

A randomized, controlled study in 2010–2011 of a pelagic area in the North Atlantic Ocean off the Azores, Portugal (Cruz et al. 2014) found that using active acoustic devices of two types did not reduce predation of squid catches by Risso’s dolphins Grampus griseus. The proportion of fishing trials in which squid were taken by Risso’s dolphins was similar with active acoustic devices (17–22%), inactive acoustic devices (17–23%) and no devices (19%). Average squid catches by fishers were also similar with active (1.5–2 squid/fisher/h), inactive (2–2.3 squid/fisher/h) and no acoustic devices (2.2 squid/fisher/h). Five squid fishing vessels (using hand lines and jigs) carried out 154 x 1 h trials during 45 fishing trips. Trials were carried out in a random order with active acoustic devices (emitting 10 kHz sounds) of each of two types (Future Oceans Fumunda Marine devices: 35 trials; Aquatec AQUAmark 300 devices: 27 trials), inactive (silent) acoustic devices (Fumunda: 35 trials; Aquatec: 25 trials) or no devices (32 trials). Acoustic devices were attached to a rope and deployed from the bow of each vessel at a depth of 60 m. Onboard observers recorded squid catches and squid predated by dolphins during each of the 154 trials in May 2010–August 2011.

(Summarised by: Anna Berthinussen)