Acoustic deterrent devices

Underwater sound-emitting devices (maximum level of intensity equivalent to approximately 175 dB re 1 µPa @ 1m) attached to fishing gear, principally gillnets. ADD’s such as acoustic pingers are now mandated for use in some fisheries in the U.S. Northwest Atlantic, California driftnet, and in Europe. The sound of these devices is believed to alert an animal to the presence of the net and thus decrease the probability of entanglement. Although some studies have shown that pingers can have the unintended consequence of attracting pinnipeds to fishing operations (Bordino et al., 2002) , this may be controllable by raising the emitted frequency of the pingers above seal hearing (Kraus et al., 1997). Other ADD’s emit sounds of such high intensity that they cause pain or alarm in certain underwater species. The minimum sound level is approximately 200 dB re 1 _Pa @ 1m (Olesiuk et al., 2002). Other ADD’s include audio recordings of an animal in distress, or of its predator, played to deter individuals of that species from entering into a fishing area. Jefferson and Curry  concluded that this technique was largely ineffective for reducing marine mammal interactions with fishing activity based on their review of multiple studies. Sounds produced to disrupt the normal echolocation abilities of cetaceans are also considered ADD’s. Preliminary research in Europe has shown some promise that these devices reduce depredation by bottlenose dolphins in gillnets and trammel nets, although habituation may be a challenge (Mooney et al. 2009) . The use of loud explosive devices, including gunshots, to scare non-target species such as sea lions away from a fishing operation can also be used. Deterrence may result from noise or tactile annoyance. Anecdotal evidence from some fishermen suggests this practice is widespread though its efficacy is not backed up by a number of studies, and it obviously threatens animal survival (Matkin 1994).

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Study Type: 

Study in the lab

Location: 

Neeltje Jans, The Netherlands

Target catch: 

n/a

Effect on bycatch species: 

Increased distance from the alarm source and respiration

Effect on target catch: 

n/a

Article: 

Study Type: 

Field study in the wild

Location: 

North Sea

Target catch: 

Hake

Effect on bycatch species: 

Pingers spaced at 455 m had 0 bycatch; pingers spaced at 585 m had a bycatch rate of 0.12

Effect on target catch: 

None reported

Article: 

Study Type: 

Field study in the wild

Location: 

North Carolina

Target catch: 

Spanish mackerel

Effect on bycatch species: 

Dolphins were less likely to interact with gillnets and more likely to echolocate

Effect on target catch: 

No effect

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Queensland, Australia

Target catch: 

Sharks

Effect on bycatch species: 

Dolphins heard the F3 pinger 45 m from the net, they could only detect the F10 pinger less than 40 m from the net

Effect on target catch: 

None reported

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Queensland, Australia

Target catch: 

Sharks

Effect on bycatch species: 

Humpback whales heard the F3 pinger 90 m from the net, they heard the F10 pinger was audible up to 130 m

Effect on target catch: 

None reported

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Cornwall

Target catch: 

None reported

Effect on bycatch species: 

There was a significant difference in the number of porpoise clicks between nets with and without pingers, but the extent of displacement could not be determined. No evidence of habituation to the pingers.

Effect on target catch: 

None reported

Article: 

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