Offshore industrial activities sometime introduce loud, impulsive sounds into the underwater environment, which have potential to affect marine mammals, for example by altering behaviour, masking of important signals or by causing temporary or permanent damage to the auditory system (reviewed by Todd et al. (2015)). Under UK legislation Conservation of Habitats and Species Regulations 2010 and the Offshore Marine Conservation Regulations 2007 it is an offense to significantly injure or disturb marine mammals, and as such, there is a requirement to mitigate against underwater noise produced during industrial operations (e.g. JNCC 2010a, c, b). Used most commonly are Marine Mammal Observers (MMO; www.marinemammalobserver.com) and Passive Acoustic Monitoring (PAM) Operators (www.pamoperator.co.uk), who visually (MMO) and/or acoustically (PAM) monitor the area for marine mammals prior to operations, ensuring the area is clear prior to start-up of the sound source.
If sounds are high intensity, for example pile driving during wind farm construction, use of additional mitigation measures such as Acoustic Deterrent Devices (ADD) may be recommended.
WHAT ARE ACOUSTIC DETERRENT DEVICES?
Acoustic Deterrent Devices (ADDs), or ‘pingers’, emit aversive sounds into the marine environment, and were developed originally to deter small cetaceans such as harbour porpoises (Phocoena phocoena) from approaching fishing gear, thus reducing entanglements. Acoustic Harassment Devices (AHDs) or ‘seal scarers’ are similar, but emit higher-intensity sounds, intended to prevent seals from approaching (and damaging) commercially important fish stocks. Both ADDs and AHDs, collectively known as Acoustic Mitigation Devices (AMD), can be used to deter marine mammals from industrial operations. The term Acoustic Harassment Device is generally discouraged these days, although the term is still used (Tixier et al. 2015).
CAN ACOUSTIC DETERRENT DEVICES DETER MARINE MAMMALS FROM OFFSHORE INDUSTRIAL SITES?
Considerable research has been conducted into the ability of Acoustic Deterrent Devices to deter marine mammals from fishing, aquaculture sites or industrial operations; results are mixed.
Avoidance responses have been observed in harbour porpoises (e.g. Johnston 2002; Olesiuk et al. 2002; Kastelein et al. 2010; Brandt et al. 2013a; Dawson et al. 2013), and in some cases, for example Brandt et al. (2013b), significant deterrent effects were recorded for porpoises 7.5. In the Broughton Archipelago in Canada, the presence of killer whales decreased when Acoustic Deterrent Devices were deployed around salmon farms over a five year period (Morton & Symonds 2002), and in the same area, Pacific white-sided dolphin (Lagenorhynchus obliquidens) presence also decreased, potentially as a result of Acoustic Deterrent Devices (Morton 2000). Deploying ‘pingers’ significantly reduced bycatch of Franciscana river dolphins (Pontoporia blainvillei) (Bordino et al. 2002) and short-beaked common dolphins (Delphinus delphis) (Barlow & Cameron 2003), whilst completely eliminating beaked whale bycatch (Carretta et al. 2008).
Conversely, in some cases, Acoustic Deterrent Devices have been known to attract marine mammals, in particular around aquaculture sites, as individuals learn to associate the sounds with a plentiful food source. For this reason, Acoustic Deterrent Devices are considered often only a short-term way of deterring seals from aquaculture sites (Nash et al. 2000). This should be taken into consideration when utilising Acoustic Deterrent Devices to deter marine mammals from industrial operations, as although seals won’t necessarily have the same motivation to approach seal scarers at offshore industrial sites, the devices could still attract them if associations with food have been created elsewhere. Even if seals aren’t initially attracted, they may tolerate, and not move as far away from, the familiar sounds of Acoustic Deterrent Devices. Therefore, Coram et al. (2014) suggested existing ‘aquaculture’ Acoustic Deterrent Devices are probably unsuitable, when mitigating the effects of industrial noise (e.g. pile driving) on seals.
REDUCING IMPACTS OF INDUSTRIAL NOISE ON MARINE MAMMALS
Overall, Acoustic Deterrent Devices seem capable of deterring at least some species of marine mammals. Further research exploring avoidance ranges of marine mammal species from Acoustic Deterrent Devices would be beneficial; including avoidance range of smaller baleen whales and seals. Additionally, further research into why some harbour porpoise have been recorded close to active seal scarers (Brandt et al. 2013b) is required, as it shows current acoustic deterrents may not always deter every individual. Therefore, combining acoustic deterrent deployments with more traditional marine mammal observations (www.marinemammalobserver.co.uk) and passive acoustic monitoring (www.passiveacousticmonitoring.com), is likely to lower the risk of commencing industrial operations when marine mammals are close to the sound source. If the risk of auditory damage is high when marine mammals are at considerable distances from the industrial site (Hastie et al. 2015), it might also be beneficial to consider dampening the noise around the source, using air bubble curtains or ‘Hydro Sound Dampers’ (e.g. Elmer et al. 2012).
OCEAN SCIENCE CONSULTING
Details on Acoustic Deterrent Devices and seal scarers supplied by Ocean Science Consulting Ltd (OSC) are available at www.osc.co.uk. OSC has experience working with Acoustic Deterrent Devices, and can provide advice on deployments including calculating the optimal number required. Contact us for more information.
Additional services include supply of Marine Mammal Observers and Passive Acoustic Monitoring Operators and equipment. For a list of all OSC’s services see www.osc.co.uk.
|Barlow J. & Cameron G.A. (2003) Field experiments show that acoustic pingers reduce marine mammal bycatch in the California|
|drift gill net fishery. Marine Mammal Science 19, 265-83.|
|Bordino P., Kraus S., Albareda D., Fazio A., Palmerio A., Mendez M. & Botta S. (2002) Reducing incidental mortality of|
|Franciscana dolphin Pontoporia blainvillei with acoustic warning devices attached to fishing nets. Marine Mammal Science 18, 833-42.|
|Brandt M.J., Hoschle C., Diederichs A., Betke K., Matuschek R. & Nehls G. (2013a) Seal scarers as a tool to deter harbour|
|porpoises from offshore construction sites. Marine Ecology Progress Series 475, 291-302.|
|Brandt M.J., Hoschle C., Diederichs A., Betke K., Matuschek R., Witte S. & Nehls G. (2013b) Far-reaching effects of a seal scarer|
|on harbour porpoises, Phocoena phocoena. Aquatic Conservation: Marine and Freshwater Ecosystems 23, 222-32.|
|Carretta J.V., Barlow J. & Enriquez L. (2008) Acoustic pingers eliminate beaked whale bycatch in a gill net fishery. Marine|
|Mammal Science 24, 956-61.|
|Coram A., Gordon J., Thompson D. & Northridge S. (2014) Evaluating and assessing the relative effectiveness of non-lethal|
|measures, including Acoustic Deterrent Devices, on marine mammals. p. 145. Scottish Government.|
|Dawson S., Northridge S.P., Waples D. & Read A. (2013) To ping or not to ping: the use of active acoustic devices in mitigating|
|interactions between small cetaceans and gillnet fisheries. Endangered Species Research 19, 201–21.|
|Elmer K.-H., Gattermann J., Kuhn C. & Bruns B. (2012) Mitigation of underwater piling noise by air filled balloons and PE-foam|
|elements as hydro sound dampers. Journal of the Acoustical Society of America 132, 2056.|
|Hastie G.D., Russell D.J.F., Mcconnell B., Moss; S., Thompson D. & Janik V.M. (2015) Sound exposure in harbour seals during|
|the installation of an offshore windfarm: predictions of auditory damage. Journal of Applied Ecology 52, 631-40.|
|JNCC (2010a) JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys. p. 16.|
|Joint Nature Conservation Committee, Aberdeen.|
|JNCC (2010b) JNCC guidelines for minimising the risk of injury to marine mammals from using explosives. p. 10. Joint Nature|
|Conservation Committee, Aberdeen, UK.|
|JNCC (2010c) Statutory nature conservation agency protocol for minimising the risk of injury to marine mammals from piling|
|noise. p. 14. Joint Nature Conservation Committee, Inverness.|
|Johnston D.W. (2002) The effect of acoustic harassment devices on harbour porpoises (Phocoena phocoena) in the Bay of|
|Fundy, Canada. Biological Conservation 108, 113-8.|
|Kastelein R.A., Hoek L., Jennings N., de Jong C.A.F., Terhune J.M. & Dieleman M. (2010) Acoustic mitigation devices (AMDs) to|
|deter marine mammals from pile-driving areas at sea: Audibility and behavioural response of a harbour porpoise and harbour seals COWRIE Ref: SEAMAMD-09, Technical Report 31st July 2010.|
|Morton A. (2000) Occurance, photo-identification and prey of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the|
|Broughton Archipelago, Canada 1984-1998. Marine Mammal Science 16, 80-93.|
|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.|
|Nash C.E., Iwamoto R.N. & Mahnken C.V.W. (2000) Aquaculture risk management and marine mammal interactions in the Pacific|
|Northwest. Aquaculture 183, 307-23.|
|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, 843-62.|
|Tixier P., Gasco N., Duhamel G. & Guinet. C. (2015) Themed Section: ‘Marine Mammal Bycatch and Depredation’. Habituation to|
|an acoustic harassment device (AHD) by killer whales depredating demersal longlines. (Orcinus orca). ICES Journal of Marine Science 72, 1673-81.|
|Todd V.L.G., Todd I.B., Gardiner J.C. & Morrin E.C.N. (2015) Marine Mammal Observer and Passive Acoustic Monitoring|
|Handbook. Pelagic Publishing Ltd, Exeter, UK.|