Use acoustic devices on moorings

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Source countries

Key messages

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (7 STUDIES)

  • Behaviour change (7 studies): Two of four controlled studies in the South Pacific Ocean, the Kyle of Sutherland estuary and the North Atlantic Ocean found that deploying acoustic devices on moorings reduced numbers of grey and harbour seals, and the activity of harbour porpoises, short-beaked common dolphins and common bottlenose dolphins. The two other studies found that using an acoustic device on a mooring did not have a significant effect on the number, direction of movement, speed, or dive durations of migrating humpback whales. One controlled study in the Bay of Fundy found that using an acoustic device on a mooring reduced harbour porpoise echolocation activity, but the probability of porpoises approaching within 125 m of the device increased over 10–11 days. One controlled study in the Shannon Estuary found that one of two types of acoustic device reduced the activity of common bottlenose dolphins. One replicated, controlled study in the Rivers Conon and Esk found that using acoustic devices reduced the number of grey and harbour seals upstream of the device but did not reduce seal numbers overall.

OTHER (1 STUDY)

  • Human-wildlife conflict (1 study): One randomized controlled study in the Puntledge River found that deploying an acoustic device on a mooring reduced the number of harbour seals feeding on migrating juvenile salmon.

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 1996 at one site in the Puntledge River, British Columbia, Canada (Yurk & Trites 2000) found that deploying an acoustic device on a mooring under a bridge reduced the number of harbour seals Phoca vitulina feeding on migrating juvenile salmon Oncorhynchus spp. compared to when no device was used. The average number of seals feeding on salmon was lower with an acoustic device deployed (0.4 seals/night) than without (8 seals/night). In May 1996, an acoustic device (Airmar Seal Scarer with four projectors) was deployed for seven nights at a river below a bridge. The projectors were suspended 40 cm below the water surface attached to ropes and floats. The device emitted 2-second sound bursts at a frequency of 27 kHz. Two observers counted seals using a red-filtered spotlight every 30 minutes from 2100–0300 h during each of seven nights with the acoustic device active and seven randomly selected nights without the device.

    Study and other actions tested
  2. A controlled study in 1998 at a pelagic site in the Bay of Fundy, Canada (Cox et al. 2001) found that an acoustic device attached to a mooring reduced harbour porpoise Phocoena phocoena echolocation activity, but the probability of porpoises approaching within 125 m of the device increased over 10–11 days. The average rate of harbour porpoise echolocation clicks and the proportion of 10-second intervals in which clicks were recorded were lower when the acoustic device was active (82 clicks/30 minutes; 0.04 intervals) than when it was inactive (516 clicks/30 minutes; 0.17 intervals). The probability of porpoises approaching within 125 m of the device initially decreased after the device was activated, then increased to equal the control (device inactive) over 10–11 days (data reported as statistical model results). An acoustic device (Dukane NetMark 1000) was attached 10 m below the water surface to a mooring located 1 km offshore. In June–September 1998, two trials were carried out in which the device was turned off (silent) for 2 weeks and turned on (emitting regular pulses at 10 kHz) for 2–4 weeks. Porpoises were tracked within a 500 m radius of the mooring using a theodolite. An acoustic detector attached to the mooring recorded porpoise echolocation clicks during one of the two trials.

    Study and other actions tested
  3. A controlled study in 2005 at six pelagic sites in the Shannon Estuary, western Ireland (Leeney et al. 2007) found that using ‘continuous’ acoustic devices on a mooring resulted in lower common bottlenose dolphin Tursiops truncatus echolocation activity compared to when inactive acoustic devices were used, but the difference was not significant for active and inactive ‘responsive’ acoustic devices. The average number of minutes in which dolphin echolocation clicks were detected was lower when ‘continuous’ acoustic devices were active (0 minutes/h; range: 0–0.05 minutes/h) than inactive (0.4 minutes/h; range: 0.2–1.1 minutes/h). The difference was not significant for ‘responsive’ acoustic devices that were active (0 minutes/h; range: 0–0.8 minutes/h) or inactive (0.6 minutes/h; range: 0.3–1.5 minutes/h). An active or inactive (silent) ‘continuous’ or ‘responsive’ acoustic device was randomly deployed at each of six sites for 3–5 x 24 h trials/treatment. ‘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. Devices were attached to a static mooring (line between an anchor and buoy), 5–12 m below the water surface. An acoustic logger recorded dolphin activity alongside the acoustic devices during each of 18 trials in July 2005.

    Study and other actions tested
  4. A replicated, controlled study in 2006–2008 at two sites in the Rivers Conon and North Esk, northeast Scotland, UK (Graham et al. 2009) found that using acoustic devices reduced the number of grey seals Halichoerus grypus and harbour seals Phoca vitulina upstream of the device but did not reduce the number of seals overall. Grey and harbour seals were observed upstream of the acoustic device during fewer surveys with the device turned on (North Esk: 5 surveys; Conon: 14 surveys) than turned off (North Esk: 9 surveys; Conon: 22 surveys). However, the overall number of seals did not differ significantly with the device turned on or off (data not reported). An acoustic device (Lofitech Seal Scarer) was deployed at each of the two rivers, 2–3 m from the bank at a depth of 2 m. The devices were turned on (emitting 500 ms pulses at 15kHz) or off (silent) for alternating periods of 1–30 days in January–May 2006 at one river and October–February 2007/2008 at the other. Both rivers (38–45 m wide) supported Atlantic salmon Salmo salar stocks. Seals were observed from the riverbank with binoculars during surveys (each lasting 1–1.5 h) with the device turned on (26–28 surveys) and off (29–36 surveys).

    Study and other actions tested
  5. A controlled study in 2008–2011 at a river site in the Kyle of Sutherland estuary, Scotland, UK (Harris 2011) found that using acoustic devices reduced the overall number of grey seal Halichoerus grypus and harbour seal Phoca vitulina sightings, and fewer seals were sighted upstream than downstream of the devices. Overall, fewer seals were sighted/hour with the acoustic devices turned on than off (data reported as statistical model results). Fewer seals were sighted upstream of the devices than downstream when they were turned on, whereas numbers were similar with the devices turned off. Two acoustic devices (Lofitech Seal Scarers) were attached to piping on the opposite sides of an estuary (100 m wide, 2 m deep), 1–10 m from the bank, 0.3–1 m above the river bed. Rivers upstream of the estuary supported Atlantic salmon Salmo salar fisheries. During each of three winters (October–January) in 2008–2011, the devices were turned on (emitting 500 ms tones at 15 kHz) and off (silent) for alternating periods of 3–13 days. Seals were guided downstream by a boat with an acoustic device prior to each ‘on’ treatment. Seals were observed from the riverbank during surveys (each lasting 2–3 h) with the devices turned on (72 surveys) and off (80 surveys).

    Study and other actions tested
  6. A controlled study in 2012–2013 at a pelagic site in the North Atlantic Ocean, off the coast of Cornwall, UK (Crosby et al. 2013) reported that when an acoustic device attached to a mooring was active, harbour porpoise Phocoena phocoena, short-beaked common dolphin Delphinus delphis and common bottlenose dolphin Tursiops truncatus echolocation activity was lower than when the device was inactive. Results are not based on assessments of statistical significance. Overall, 45 porpoise clicks/h and 4.9 dolphin clicks/h were recorded within 150 m of the mooring when the acoustic device was active, compared to 73 porpoise clicks/h and 6.6 dolphin clicks/h when the device was inactive. An acoustic device (Fishtek Banana Pinger) was attached to a fixed mooring in 40 m of water. The pinger was active (emitting 300 ms sounds at random intervals of 4–12 seconds with random frequencies between 50–120 kHz) and inactive (silent) for alternating 21 h periods. An acoustic logger deployed 150 m from the mooring recorded porpoise and dolphin echolocation clicks while the acoustic device was active (total 1,547 h) and inactive (total 1,420 h) between July 2012 and April 2013.

    Study and other actions tested
  7. A controlled study in 2012 of a pelagic site in the South Pacific Ocean, Australia (Harcourt et al. 2014; same study area as Pirotta et al. 2016) found that when an acoustic device was deployed on a mooring, a similar number of migrating humpback whale Megaptera novaeangliae pods passed when the device was turned on or off, and the direction of whale pod movement and dive durations were also similar. The total number of whale pods passing within range (500 m) of the device did not differ significantly when the device was turned on (51 of 78, 65%) or off (31 of 59, 52%). The same was true for the average direction of whale pod movement (device on: 20° from north; device off: 19° from north) and average dive duration (device on or off: both 1.3 minutes). The acoustic device (Fumunda F3 Whale Pinger) was deployed at a depth of 5 m on a fixed mooring 1.3 km offshore in the centre of a whale migration route. The device was turned on (emitting 300 ms pulses at 3 kHz) for 18 days and off (silent) for 16 days. A total of 137 migrating whale pods were tracked from the shore using a theodolite during 430 h in June–August 2012.

    Study and other actions tested
  8. A controlled study in 2013 of a pelagic site in the South Pacific Ocean, Australia (Pirotta et al. 2016; same study area as Harcourt et al. 2014) found that an active acoustic device deployed on a mooring did not have a significant effect on the movement, speed or dive durations of migrating humpback whale Megaptera novaeangliae pods. Whale pods that passed within range (500 m) of the acoustic device had a similar direction of movement, speed and dive durations when the device emitted 2 kHz tones (23° from north; 1.9 m/s; 5 minutes), 5.3 kHz tones (23° from north; 1.6 m/s; 7 minutes) or was inactive (22° from north; 1.9 m/s; 5 minutes). An acoustic device (an iPod attached to an amplifier and loudspeaker) was deployed at a depth of 5 m on a fixed mooring 1.3 km offshore in the centre of a whale migration route. During 11 h/day, the device emitted either 1.5 second tones every 8 seconds at 2–2.1 kHz (total 10 days), 400 ms tones every 5 seconds at 5.3 kHz (total 11 days) or was inactive (silent; total 12 days). A total of 108 migrating whale pods were tracked from the shore using a theodolite over the 33 days in June–August 2013.

    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.

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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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