Use acoustic devices on fishing vessels

How is the evidence assessed?
  • Effectiveness
    40%
  • Certainty
    50%
  • Harms
    20%

Study locations

Key messages

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (4 STUDIES)

  • Behaviour change (4 studies): One controlled study in the Shannon Estuary found that common bottlenose dolphins avoided a boat more frequently when acoustic devices of two types were deployed alongside it. One controlled study in the Indian Ocean found that killer whales were recorded further from a fishing vessel when an acoustic device was used during hauls, but distances decreased after the first exposure to the device. Two before-and-after studies in the Rainbow Channel and Keppel Bay found that an acoustic device deployed alongside a vessel reduced surfacing and echolocation rates and time spent foraging or socializing of Indo-Pacific humpback dolphins and Australian snubfin dolphins but there was no effect on 8–10 other types of behaviour (e.g. vocalizing, diving, travelling etc.).

OTHER (1 STUDY)

  • Human-wildlife conflict (1 study): One randomized, controlled study in the North Atlantic Ocean found that using acoustic devices of two types did not reduce predation of squid catches by Risso’s dolphins.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A controlled study in 2005 of a pelagic area in the Shannon Estuary, western Ireland (Leeney et al. 2007) reported that deploying active ‘continuous’ or ‘responsive’ acoustic devices alongside a boat resulted in common bottlenose dolphins Tursiops truncatus avoiding the boat more frequently than when inactive acoustic devices were deployed. Results are not based on assessments of statistical significance. Dolphins avoided a boat during more trials with active ‘continuous’ devices (3 of 4 trials) and active ‘responsive’ devices (3 of 4 trials) than with inactive ‘continuous’ devices (1 of 4 trials) or inactive ‘responsive’ devices (0 of 1 trial). Active ‘continuous’ or ‘responsive’ acoustic devices were deployed from the back of a 5.4-m rigid inflatable boat for four trials each. Inactive (silent) ‘continuous’ and ‘responsive’ acoustic devices were deployed for four trials and one trial respectively. Dolphin groups were approached to 50 m prior to the deployment of each device. ‘Continuous’ devices (Loughborough University/Aquatech prototype) continuously emitted sounds (<1 second sounds every 5–20 seconds at 5–20 kHz). ‘Responsive’ devices (Aquatec AquaMark) emitted sounds (300 ms sounds at 35–160 kHz) when dolphin clicks were detected by an internal microphone. Dolphin behaviour was observed for four minutes during each of the 13 trials in July 2005.

    Study and other actions tested
  2. A before-and-after study in 2007–2008 at a pelagic site in the Rainbow Channel, Queensland, Australia (Soto et al. 2013) found that during and after an acoustic device was deployed alongside a vessel, Indo-Pacific humpback dolphins Sousa chinensis spent less time foraging and had reduced surfacing and echolocation rates compared to before the device was deployed, but eight other types of behaviour did not differ. Three types of dolphin behaviour (percentage of time spent foraging, active surfacing rates, echolocation click rates) were reduced during and after an acoustic device was deployed compared to before (data reported as statistical model results). Eight other types of behaviour (percentage of time spent travelling, socializing or vocalizing; rate of blows, dives, whistles, burst pulses or other behaviours) did not differ significantly before, during or after an acoustic device was deployed. An acoustic device (Fumunda acoustic alarm) was deployed alongside a stationary research vessel during a total of 17 trials near 37 dolphin groups (1–3 dolphins/group). Each trial had three 10-minute periods with no device, an active device submerged (emitting 300 ms pulses every 4 seconds at 10 kHz), and the device removed from the water. Dolphin behaviour was observed from the vessel and vocalizations were recorded with a hydrophone submerged at a depth of 3 m during each of the 17 trials in September 2007–April 2008.

    Study and other actions tested
  3. A before-and-after study in 2007–2008 at a river mouth in Keppel Bay, Queensland, Australia (Soto et al. 2013) found that deploying an acoustic device alongside a vessel reduced the percentage of time Australian snubfin dolphins Orcaella heinsohni spent socializing compared to before a device was deployed, but 10 other types of behaviour did not differ. Snubfin dolphins spent less time socializing during and after an acoustic device was deployed compared to before (data reported as statistical model results). Ten other types of behaviour (time spent foraging, travelling or vocalizing; rate of active surfacing, blows, dives, whistles, burst pulses, clicks or other behaviours) did not differ significantly before, during or after an acoustic device was deployed. An acoustic device (Fumunda acoustic alarm) was deployed alongside a stationary research vessel during a total of 10 trials near 13 dolphin groups (1–5 dolphins/group). Each trial had three 5-minute periods with no device, an active device submerged (emitting 300 ms pulses every 4 seconds at 10 kHz), and the device removed from the water. Dolphin behaviour was observed from the vessel and vocalizations were recorded with a hydrophone submerged at a depth of 3 m during each of the 10 trials in September 2007–April 2008.

    Study and other actions tested
  4. 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.

    Study and other actions tested
  5. A controlled study in 2011 of a pelagic area in the southern Indian Ocean off the Crozet Islands (Tixier et al. 2015) found that when an acoustic device was turned on during fishing hauls, killer whales Orcinus orca were recorded further from the fishing vessel than when the device was turned off, but distances decreased after the first exposure to the device. Killer whales of two family groups were recorded at greater distances from the fishing vessel during hauls when an acoustic device was turned on for the first time (average 933 m) compared to when it was turned off (average 277 m). Average distances to the vessel decreased significantly during successive exposures to the acoustic device for both groups (first exposure: 800–1,000 m; after 5–22 exposures: 90–240 m). In February 2011, a fishing vessel targeting Patagonian toothfish Dissostichus elegenoides deployed an acoustic device (comprising 40 transducers placed 8–10 m below the vessel) during hauls of 23 ‘long lines’ (each 5.4 km long with 4,500 hooks) with killer whales present. During 15–20-minute intervals, the device was alternately turned off (silent; total 31 intervals) or on (emitting 0.5–1 second sounds at 6.5 kHz; total 45 intervals). An onboard observer recorded the distance of killer whales from the vessel. Individuals within two family groups were identified from photographs.

    Study and other actions tested
Please cite as:

Berthinussen, A., Smith, R.K. and Sutherland, W.J. (2021) Marine and Freshwater Mammal Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Marine and Freshwater Mammal Conservation

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Marine and Freshwater Mammal Conservation
Marine and Freshwater Mammal Conservation

Marine and Freshwater Mammal Conservation - Published 2021

Marine and Freshwater Mammal Synopsis

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