Seal scarers as a tool to deter harbour porpoises from offshore construction sites

Brandt, Miriam; Höschle, Caroline; Diederichs, Ansgar; Betke, Klaus; Matuschek, Rainer; Nehls, Georg

doi:10.3354/meps10100

Cited by 42 publications

(30 citation statements)

References 18 publications

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“…The low‐frequency components of the signal measured at 20 m distance did not significantly exceed the detection threshold of the farmed fish (see Hawkins & Johnstone, , for audiogram). In previous studies harbour porpoises have been shown to respond to sounds at a relatively low RL at frequencies between 8 and 80 kHz (Johnston, ; Kastelein et al ., ; Brandt et al ., ). Since harbour porpoises did not respond to our playbacks, we feel confident that results would be similar with other odontocete species, such as bottlenose dolphins Tursiops truncatus or long‐finned pilot whales Globicephala melas , which have a broadly similar hearing sensitivity to harbour porpoises but generally seem to tolerate noise much better (Cox et al ., ; Antunes et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Non‐lethal management of carnivore predation: long‐term tests with a startle reflex‐based deterrence system on a fish farm

Götz

Janik

2016

Animal Conservation

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Carnivore depredation on human livestock is a worldwide problem with few viable solutions. Non-lethal management tools such as acoustic devices show highly varying success and often pose a conservation risk due to noise pollution and habitat degradation. We tested the long-term effectiveness of a deterrence system which harnesses an autonomous reflex (startle) to selectively inflict avoidance responses in a target species (phocid seals) by emitting band-limited noise pulses with sharp onset times. Seal predation was monitored at a marine salmon farm (test site) over a full production cycle (19 month) with a multitransducer deterrent system deployed for the final year. Predation was also monitored for several months at two control sites and additional short-term tests were carried out at sites which suffered higher predation rates. Generalized linear (mixed) models revealed that sound exposure caused a 91% reduction in lost fish when comparing predation levels within the test site and 97% when comparing the test site against both control sites. Similarly, sound exposure led to a 93% reduction in the number of fish lost due to seal damage at a short-term test site. Visual monitoring of marine mammals around the long-term test site showed that the number of seal surfacings within 100 m from the loudspeakers was only slightly lower during sound exposure. Harbour porpoise and otter distribution around the farm was not affected by sound exposure. By adjusting the frequency composition of startle stimuli, our method has the potential to provide solutions for managing human-wildlife conflicts in terrestrial and marine habitats by selectively deterring target species.

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Section: Discussionmentioning

confidence: 97%

Non‐lethal management of carnivore predation: long‐term tests with a startle reflex‐based deterrence system on a fish farm

Götz

Janik

2016

Animal Conservation

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“…Seal scarers have been shown to effectively displace porpoises several kilometres (Brandt et al 2012(Brandt et al , 2013 and the cumulated noise exposure from pile-driving noise is therefore substantially reduced, minimizing the number of porpoises at risk of developing TTS. The results from DanTysk indicate that the seal scarer indeed deterred porpoises, up to a distance of at least 12 km and perhaps even 18 km from the pile driving, seen as a significant reduction in %PPM (Fig.…”

Section: Discussionmentioning

confidence: 99%

Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises

Dähne¹,

Tougaard²,

Carstensen³

et al. 2017

Mar. Ecol. Prog. Ser.

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Effects of constructing the DanTysk offshore wind farm (German Bight, 80 turbines, 6 m diameter foundations) were studied by passive acoustic monitoring of pile-driving noise and harbour porpoise Phocoena phocoena echolocation. An acoustic deterrence device (seal scarer) was used to protect porpoises from hearing loss and bubble curtains were used to attenuate the pile-driving noise. Porpoise occurrence, quantified by echolocation signals, decreased when the seal scarer was engaged, during pile driving and up to 5 h after pile driving stopped. This effect extended out to 12 km, less than the 18−25 km reported from other pile drivings performed without bubble curtains. The bubble curtains thus effectively reduced the temporary habitat loss and risk of hearing loss. The 2 bubble curtains each attenuated the noise by between 7 and 10 dB, when used separately, and 12 dB when used together. Attenuation was most pronounced above 1 kHz, where the pile-driving noise at larger distances was comparable to or lower than ambient noise. This suggests that noise regulation should be based on frequency-weighted sound levels in addition to broadband levels, to assure that mitigation measures are effective in reducing impact on animals and not only in fulfilling legal requirements. The strong reaction to the seal scarer raises concern that it may surpass the reactions to the pile-driving noise itself, when operating with bubble curtains, and calls for a re-evaluation of the specifications of seal scarer sounds.

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“…Acoustic deterrent devices are known to have far‐reaching effects in the absence of piling noise (Brandt et al. , b). Efforts to optimize assessment and mitigation measures during anticipated increases in coastal construction activity (Bulleri and Chapman ) therefore require better understanding of the relative influence of different high‐frequency (ADD) and lower‐frequency piling noise sources on behavioral responses.…”

Section: Discussionmentioning

confidence: 99%

Responses of bottlenose dolphins and harbor porpoises to impact and vibration piling noise during harbor construction

et al. 2017

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Abstract. The development of risk assessments for the exposure of protected populations to noise from coastal construction is constrained by uncertainty over the nature and extent of marine mammal responses to man-made noise. Stakeholder concern often focuses on the potential for local displacement caused by impact piling, where piles are hammered into the seabed. To mitigate this threat, use of vibration piling, where piles are shaken into place with a vibratory hammer, is often encouraged due to presumed impact reduction. However, data on comparative responses of cetaceans to these different noise sources are lacking. We studied the responses of bottlenose dolphins and harbor porpoises to both impact and vibration pile driving noise during harbor construction works in northeast Scotland, using passive acoustic monitoring devices to record cetacean activity and noise recorders to measure and predict received noise levels. Local abundance and patterns of occurrence of bottlenose dolphins were also compared with a five-year baseline. The median peak-to-peak source level estimated for impact piling was 240 dB re 1 lPa (single-pulse sound exposure level [SEL] 198 dB re 1 lPa 2 s), and the r.m.s. source level for vibration piling was 192 dB re 1 lPa. Predicted received broadband SEL values 812 m from the piling site were markedly lower due to high propagation loss: 133.4 dB re 1 lPa 2 s (impact) and 128.9 dB re 1 lPa 2 s (vibration). Bottlenose dolphins and harbor porpoises were not excluded from sites in the vicinity of impact piling or vibration piling; nevertheless, some small effects were detected. Bottlenose dolphins spent a reduced period of time in the vicinity of construction works during both impact and vibration piling. The probability of occurrence of both cetacean species was also slightly less during periods of vibration piling. This work provides developers and managers with the first evidence of the comparative effects of vibration and impact piling on small cetaceans, enabling more informed risk assessments, policy frameworks, and mitigation plans. In particular, our results emphasize the need for better understanding of noise levels and behavioral responses to vibration piling before recommending its use to mitigate impact piling.

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Seal scarers as a tool to deter harbour porpoises from offshore construction sites

Cited by 42 publications

References 18 publications

Non‐lethal management of carnivore predation: long‐term tests with a startle reflex‐based deterrence system on a fish farm

Non‐lethal management of carnivore predation: long‐term tests with a startle reflex‐based deterrence system on a fish farm

Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises

Responses of bottlenose dolphins and harbor porpoises to impact and vibration piling noise during harbor construction

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