Use acoustic devices to deter marine and freshwater mammals from an area to reduce noise exposure
Overall effectiveness category Trade-off between benefit and harms
Number of studies: 4
Background information and definitions
Activities that produce large amounts of underwater noise, such as seismic airgun surveys, pile driving, dredging, explosives and sonar, may disturb or cause auditory injury to marine and freshwater mammals (Gordon et al. 2003, Bailey et al. 2010). Acoustic devices may be used to deter marine or freshwater mammals from an area prior to commencing such activities to reduce potential harm. However, it should be noted that high amplitude acoustic devices may cause hearing damage to target and non-target mammal species, and may disrupt biologically important behaviour or exclude mammals from important habitats (Johnston 2002, Morton & Symonds 2002, Olesiuk et al. 2002, Götz & Janik 2013).
Bailey H., Senior B., Simmons D., Rusin J., Picken G. & Thompson P.M. (2010) Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals. Marine Pollution Bulletin, 60, 888–897.
Gordon J., Gillespie D., Potter J., Frantzis A., Simmonds M.P., Swift R. & Thompson D. (2003) A review of the effects of seismic surveys on marine mammals. Marine Technology Society Journal, 37, 16–34.
Götz T. & Janik V.M. (2013) Acoustic deterrent devices to prevent pinniped depredation: efficiency, conservation concerns and possible solutions. Marine Ecology Progress Series, 492, 285–302.
Johnston D.W. (2002) The effect of acoustic harassment devices on harbour porpoises (Phocoena phocoena) in the Bay of Fundy, Canada. Biological Conservation, 108, 113–118.
Morton A.B. & Symonds H.K. (2002) Displacement of Orcinus orca (L.) by high amplitude sound in British Columbia, Canada. ICES Journal of Marine Science, 59, 71–80.
Olesiuk P.F., Nichol L.M., Sowden M.J. & Ford J.K.B. (2002) Effect of the sound generated by an acoustic harassment device on the relative abundance and distribution of harbor porpoises (Phocoena phocoena) in Retreat Passage, British Columbia. Marine Mammal Science, 18, 843–862.
Supporting evidence from individual studies
A controlled study in 2009 of a pelagic area in the North Sea, Germany (Brandt et al. 2013) found that deploying an active acoustic device reduced harbour porpoise Phocoena phocoena echolocation activity and sightings at distances up to 7.5 km from the device. The average percentage of minutes/h with porpoise activity was lower with the acoustic device turned on than turned off at distances of 0 m (0.1% vs 2.6% respectively), 750 m (0.6% vs 4%), 3 km (2.5% vs 10.2%) and 7.5 km (0.1% vs 3.1%) from the device. The difference was not significant at 1.5 km (1.1% vs 2.4%) or 5 km (0.8% vs 0.9%). Fewer porpoises were observed in the study area with the device turned on (average 0.3 porpoises/km2) than off (average 4 porpoises/km2). In July–November 2009, an acoustic device (Lofitech Seal Scarer) was tested by deploying it from an anchored boat 80 km offshore, 7–10 m below the water surface. The device was turned on (emitting 0.5 second pulses at a frequency of 14 kHz) for 10 x 4-h trials, each separated by at least four days with the device turned off (silent). Sixteen acoustic detectors arranged in a star pattern recorded porpoise echolocation clicks at distances of 0 m, 750 m, 1.5 km, 3 km, and 7.5 km from the acoustic device. Data were compared for 3 h before and 3 h during each of the 10 trials. On 10 August 2009, two observers recorded porpoise sightings along 30 aerial transects over a 990 km2 area before and after the acoustic device was turned on.Study and other actions tested
A randomized, controlled study in 2010–2011 of a pelagic site in the Great Belt, Denmark (Brandt et al. 2013) found that when an active acoustic device was deployed, fewer harbour porpoises Phocoena phocoena were sighted within 1 km of the device. The average number of porpoise sightings was lower with the acoustic device turned on than turned off at distances of 0–150 m (0 vs 2 sightings/4h respectively), 151–450 m (0 vs 8 sightings/h) and 451–1,000 m (0.3 vs 20 sightings/h) from the device. Six porpoises also avoided the active device at distances of 1.1–2.4 km, and six porpoises had no obvious reaction at distances of 2.1–3.3 km (see original paper for details). In May–August 2010, an acoustic device (Lofitech Seal Scarer) was tested by deploying it from an anchored boat 150 m offshore, 4 m below the surface in water 2–15 m deep. The device was randomly turned on (emitting 0.6 second pulses at 14.5 kHz with random pauses of <1–90 seconds) or off (silent) during a total of seven and four days respectively. Porpoises within 1 km were observed and tracked with a theodolite from a cliff. Additional observations were made during three days in September 2010 and one day in August 2011, in which the device was deployed 1.1–3.3 km offshore and activated for 15 x 5-minute intervals.Study and other actions tested
A before-and-after study in 2013 at a wind farm construction site in the North Sea, Germany (Dähne et al. 2017) found that using acoustic devices reduced harbour porpoise Phocoena phocoena activity prior to pile driving within 18 km of the site. At distances of 1.5–12 km and 15–18 km from the site, the average percentage of minutes with porpoise clicks detected was lower during periods in which acoustic devices were used (1.5–12 km: 1–5%; 15–18 km: 3%) compared to before devices were used (1.5–12 km: 4–7%; 15–18 km: 5%). At distances of 12–15 km, the difference was not significant (before: 4%; during: 3%). In February–December 2013, acoustic devices were used during 0.5–4 h periods prior to pile driving for 80 wind turbine foundations. Acoustic devices were Aquatec AQUAmark 100 pingers (emitting sounds at 20–160 kHz) and a Lofitech Seal Scrammer (emitting 0.5 second sounds at 14 kHz). Twelve acoustic detectors placed 1–31 km from the site recorded porpoise echolocation clicks for periods before (3 h) and during acoustic device use (0.5–4 h) for each of the 80 foundations.Study and other actions tested
A before-and-after study in 2016 of a pelagic area in Faxaflói Bay, Iceland (McGarry et al. 2017) found that when an acoustic device was deployed, minke whales Balaenoptera acutorostrata swam away from the device, increased their swimming speed and swam more directly than before the device was deployed, although two of seven returned to the area soon after the device was turned off. All of 15 minke whales swam away from the acoustic device during 15 minutes in which it was active. The average swimming speed of the 15 tracked whales was greater while the device was active (15 km/h) than before (8 km/h), and the whales swam more directly (data reported as directness indices). Two of seven whales tracked for 30 minutes after the device was turned off returned to the area within 10–15 minutes. In August–September 2012, an acoustic device (Lofitech Seal Scarer) was deployed at a potential wind farm site during 15 trials from a 4.2-m rigid inflatable boat at distances of 300–1,500 m from minke whales. During each trial, the device was turned on (emitting 500 ms pulses at random intervals and frequencies of 10–20 kHz) for 15 minutes. Each of 15 whales was tracked from a research vessel using a video system for 45 minutes before, 15 minutes during and 30 minutes after (seven whales only) the device was activated.Study and other actions tested