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).

Displaying 31 - 40 of 73

Study Type: 

Field study in the wild

Location: 

Cornwall

Target catch: 

Monkfish

Effect on bycatch species: 

One incidentally caught harbor porpoise; significant reduction in the number of porpoise clicks at nets with pingers. Pinger effects stronger at quiet sites; no habituation observed, exclusion of porpoises following pinger use for as much as 7 hrs

Effect on target catch: 

None reported

Article: 

Study Type: 

Field study in the wild

Location: 

Southwest England

Target catch: 

None reported

Effect on bycatch species: 

DDD's caught significantly fewer porpoises but no significant difference in dolphin bycatch was observed

Effect on target catch: 

None reported

Article: 

Study Type: 

Field study in the wild

Location: 

Baltic

Target catch: 

None reported

Effect on bycatch species: 

Pingers significantly reduced echolocation encounter rates by 50-100% at 500m; sighting reduced up to 375m. Porpoise return time was 6 hrs when pingers were silent after being active for 24 hrs 50 min

Effect on target catch: 

None reported

Article: 

Study Type: 

Field study in the wild

Location: 

North Sea

Target catch: 

Cod

Effect on bycatch species: 

Reduced catch rates from 0.00229 and 0.00295 for nets with dummy pingers and no pingers respectively, to 0.00015 for nets with active pingers

Effect on target catch: 

None reported

Article: 

Study Type: 

Field study in the wild

Location: 

Turkey

Target catch: 

turbot fish

Effect on bycatch species: 

Reduced harbor porpoise interactions with gillnet

Effect on target catch: 

Use of pingers did not signficiantly affect catch rates or size of fish caught

Article: 

Study Type: 

Field study in the wild

Location: 

North Carolina, USA

Target catch: 

Mixed

Effect on bycatch species: 

No difference on group size or closest approach to the net between active and control pingers

Effect on target catch: 

None

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

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