Pingers as deterrents of bottlenose dolphins interacting with trammel nets

Published source details Gazo M., Gonzalvo J. & Aguilar A. (2008) Pingers as deterrents of bottlenose dolphins interacting with trammel nets. Fisheries Research, 92, 70-75.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices on fishing gear Action Link

Use acoustic devices on fishing gear

A controlled study in 2001 of a pelagic area in the Mediterranean Sea, off the Balearic Islands, Spain (Gazo et al. 2008) found that using acoustic devices on fishing nets reduced damage to nets and fish caused by common bottlenose dolphins Tursiops truncatus. Fishing nets with active acoustic devices had significantly fewer holes (average 1 hole/net) than nets with inactive acoustic devices (average 8 holes/net) or no devices (average 6 holes/net). The percentage of caught fish bitten by dolphins was also lower in nets with active devices (7%) compared to inactive devices (13%) or no devices (17%), although statistical significance was not assessed. Catch rates of target red mullet Mullus surmuletus did not differ significantly between nets with active devices (0.6 kg/net), inactive devices (0.7 kg/net) and no devices (0.9 kg/net). A total of 55 trammel net deployments (each with multiple nets, 50 m long x 2 m high, tied together) were deployed across a fishing area (340 km²). One of three treatments was rotated between deployments: active acoustic devices attached (27 deployments), inactive (silent) acoustic devices attached (16 deployments) or no devices (12 deployments). Acoustic devices (Aquatec AQUAmark 100; emitting eight different signals of 5–30 second duration at 20–160 kHz) were attached at 150 m intervals. An observer on board each of three fishing vessels recorded fish catches, dolphin-damaged fish and new holes in the nets during each of the 55 hauls in September–October 2001.

(Summarised by: Anna Berthinussen)