Publication - Progress report
Aquaculture - Acoustic Deterrent Device (ADD) use: parliamentary report
Report to the Scottish Parliament on the use of acoustic deterrent devices by the Scottish aquaculture sector at finfish farms as required by section 15 of the Animals and Wildlife (Penalties, Protection and Powers) (Scotland) Act 2020.
Appendix
| Device | Species | Study type | Study Summary | Reference(s) |
|---|---|---|---|---|
| Airmar 'dB Plus II' | Minke Whale | Anecdotal | There is anecdotal evidence in Fairbairns et al. (1994; taken from Gordon and Northridge, 2002) that a minke whale was not displaced or deterred by an Airmar ADD. In this case, a minke whale entered a small sealoch on the Isle of Lewis and remained there for ten weeks, apparently feeding on dense schools of fish. A fish farm within the loch used an ADD, which had a signal that closely matched that of an Airmar dB Plus II device (Gordon and Northridge, 2002). The ADD was not active when the whale entered the loch, and when activated, behavioural observations suggested the animal changed from a resting to a feeding mode but still continued to use all areas of the Loch and even appeared to investigate the device on one occasion. This event suggests that the minke whale was not deterred by the presence of an active device, although this was not a controlled study. Furthermore, the acoustic characteristics of the device are unknown and the observation relates to a single animal. | Fairbairns et al., 1994; Gordon & Northridge 2002 |
| GenusWave 'Unknown' | Minke Whale | Anecdotal / Field Study | During field trials of the GenusWave device at a fish farm on the west coast of Scotland, six minke whales were sighted during sound exposure periods and one during control periods. The closest observed approach for a minke whale was 1109 m during sound exposure and this whale was observed heading into the bay where the fish farm was located. This study provides limited data for minke whales due to the sample size, but found there was no evidence for any impacts at distances of more than 1 km. However, the RL at the distance of the closest observed approach was relatively low (125 dB re 1 µPa (RMS)). | Götz & Janik, 2015 |
| Lofitech 'Seal Scarer' | Minke Whale | Field Study | A controlled exposure experiment (CEE) using the Lofitech device in Iceland tracked the behaviour of minke whales during control, treatment and post-treatment phases. During each experimental exposure, a whale was visually observed for 30 mins to record baseline behaviour (control phase), then a single ADD was lowered into the water for 15 mins (exposure phase), then finally the whale was observed for a final 30 minutes once following the removal of the ADD (post-exposure phase). In all 15 cases of the ADD being deployed at a distance of 1 km, the focal animal moved away from the sound source. There was a significant increase in net swim speed (7.4 kmh-1) and directionality during deployment. Notably trials deploying the device at a closer distance of 500 m resulted in such strong aversive reactions that some focal animals disappeared too rapidly to be tracked for the remainder of the CEE (n=4). The SL was measured at 198 dB re 1 µPa @ 1 m (RMS), with a fundamental frequency of 14.6 kHz and an average pulse length of 752 ms. This SL is much higher than the manufacturers stated SL (191 dB re 1 µPa @ 1 m) and much higher than the Basran et al., 2020 study below (188 dB re 1 µPa @ 1 m). | McGarry et al., 2017 |
| Humpback Whale | Field Study | Boat-based studies of humpback whales in Iceland examined behavioural responses to a Lofitech device. The device had a measured SL of 188 dB re 1 µPa @ 1 m (RMS), with a fundamental frequency of 14.5 kHz and a frequency range between 10 to 20 kHz, for pulses of 500 ms duration at random intervals of 5 to 60 s. During each experimental exposure, a whale was visually observed for 30 mins to record baseline behaviour (control phase), then a single ADD was lowered into the water for 15 mins (exposure phase), then finally the whale was observed for a final 30 mins following the removal of the ADD (post-exposure phase). There were seven exposures for six individuals (one individual tested twice, with 18 months between exposures). There were no significant behavioural changes observed in swim speed and directness, breathing rate or dive time, and this was consistent across all seven exposures. | Basran et al., 2020 |
| Device | Species | Study Type | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Killer Whale & Bottlenose Dolphin | Noise Modelling | Desk-based noise modelling of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal species. The maximum audible range was based on a sea state of 0 and water depths of 10-50 m. SL of the ADDs were based on Lepper et al. (2014). Modelling suggested that the Ace-Aquatec ADD sound was audible, to killer whales between 33-70 km and to bottlenose dolphins between 33-63 km, depending on sea state and water depth. While audible does not directly infer disturbance, the authors suggested that noise from the ADDs could reach a behavioural disturbance level (defined as 140–180 dB re 1 µPa (RMS)) (Southall et al., 2007) within a radius of 1.3 km. | Todd et al., 2019 |
| Airmar 'dB Plus II' | Killer Whale & Bottlenose Dolphin | Noise Modelling | Desk-based noise modelling by Todd et al. (2019) of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal hearing groups. The maximum audible range was based on a sea state of 0 and depths of 10-50 m, and SL for the ADDs were based on Lepper et al. (2014). Modelling suggested that the Ace Aquatec ADD sound is audible to killer whales between 30-78 km and to bottlenose dolphins between 31-58 km, depending on sea state, and the sounds could potentially reach a behavioural disturbance level (140–180 dB re 1 µPa (RMS)) (Southall et al., 2007) within a radius of 1.3 km. | Todd et al., 2019 |
| Airmar 'Unknown' | Killer Whale | Field Study | Two long-term studies in British Columbia, Canada monitored killer whale presence between 1985-2000 in two adjacent areas that had stable killer whale populations. Four Airmar ADDs with a SLs of 194 dB re 1 µPa @ 1 m at a frequency of 10 kHz were deployed between 1993-1999 at existing salmon farms in one of the areas. In the control area where no ADDs were deployed, sightings were not significantly different during the years of ADD activity (mean = 192.40, s.d. = 8.26, n = 5) to those of both pre-exposure (mean = 166.78, s.d. = 30.85, n = 9) and post-exposure (mean = 169.00, s.d. = 15.56, n = 2) periods, but did show a slight increase during the exposure period. This is in contrast to the exposure area, where sightings were significantly lower (by a factor of 3) during the years of ADD activity (mean = 9.80, s.d. = 4.97, n = 5), than those of both the pre-exposure (mean = 33.00, s.d. = 12.35, n = 9) and post-exposure (mean = 31.50, s.d. = 3.54, n = 2) periods. The authors suggest that animals were displaced from the exposure area into the control area during the six years where the ADDs were deployed, with killer whale presence then returning to pre-exposure levels once the devices were removed in 1999. | Morton & Symonds, 2002 |
| Pacific White-sided Dolphin | Field Study | Surveys of Pacific white-sided dolphins in British Columbia, Canada between 1984-1998 reported that the abundance of dolphins declined following introduction of Airmar ADDs into the study area. Different methods were used to detect dolphins including passive acoustic monitoring (PAM) (55% sightings), reports from vessels (19%) boat searches (18%) and visual scans (8%) between 1984-1998 (14 years). The authors state that the reduction in sightings in the latter part of the study period (from 1994 through 1998) corresponded with a general decline in sightings of other cetacean in the Broughton Archipelago since January 1994. This trend was noted to have coincided with the introduction of four Airmar ADDs to the area (described above in Morton & Symonds 2002, with the acoustic characteristics described in more detail by Haller and Lemon 1994) by the salmon farming industry. | Morton, 2000 | |
| GenusWave 'Unknown' | Harbour Porpoise | Field Study | Field trials with the GenusWave ADD (SL: 176–179 dB re 1 µPa @ 1 m) at a fish farm on the west coast of Scotland found no significant effect of sound exposure on the number of harbour porpoise surfacings observed within 200 m from the closest ADD, and overall porpoise abundance remained unaffected. At 20 m, none of the 1/3 octave bands exceeded the hearing threshold of a porpoise by more than 72 dB re 1 µPa (typically insufficient for eliciting significant startle responses in mammals). Given that these results demonstrate that harbour porpoise abundance was unaffected by the sound exposure, the authors expect that there would be similarly negligible effects for other odontocetes such as bottlenose dolphins and pilot whales. However there has been no research, either in captivity or in the field, on the effect of the GenusWave device on high-frequency cetaceans. | Götz & Janik, 2015 & 2016 |
| Terecos 'DSMS-4' | Killer Whale & Bottlenose Dolphin | Noise Modelling | Desk-based noise modelling by Todd et al. (2019) of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal species. The maximum audible range was based on a sea state of 0 and water depths of 10-50 m and SLs for the ADDs were based on measurements from Lepper et al. (2014). Models suggest the Terecos ADD sound is audible to killer whales between 37-110 km and to bottlenose dolphins between 37-89 km, depending on sea state, and the sounds could potentially reach a behavioural disturbance level (140–180 dB re 1 µPa (RMS)) (Southall et al., 2007) within a radius of 1.3 km. | Todd et al., 2019 |
| Device | Species | Study Type | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Harbour Porpoise | Noise Modelling | Desk-based noise modelling by Todd et al. (2019) of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal species. The maximum audible range was based on a sea state of 0 and depths of 10-50 m and SLs for the ADDs were based on Lepper et al. 2014. Models suggest the Ace Aquatec ADD sound is audible to harbour porpoise between 34-68 km, depending on sea state, and the sounds could potentially reach a behavioural disturbance level (140–180 dB re 1 µPa (RMS)) (Southall et al., 2007) within a radius of 1.3 km. | Todd et al., 2019 |
| Ace-Aquatec 'Seal Scrammer' | Harbour Porpoise | Captive Study | Playback experiments with captive harbour porpoise estimated the audibility and behavioural response to signals from different ADD types. The effect of different received broadband SPLs were identified; a level that did not cause a behavioural change (77 dB re 1 µPa), a level that caused a small change in the surfacing rate and swimming pattern (117 dB re 1 µPa) and a level that caused the porpoise to swim away from the ADDs (i.e., exhibit displacement) (139 dB re 1 µPa). Depending on sea conditions and based on noise modelling, the Ace Aquatec ADD was expected to be audible to porpoise between 14-91 km and likely to deter porpoises at ranges between 0.2-1.2 km based on porpoise hearing thresholds (stimulus levels resulting in a 50% detection rate). | Kastelein et al., 2010 |
| Harbour Porpoise | Captive Study | Another captive study of the ability of porpoise to hear ADD sounds was carried out with two types of ADD, including the Ace-Aquatec. As the mean received SPL was increased in the pool, displacement occurred with increased surfacing, swimming speed and jumping for the captive porpoise. These behavioural reactions occurred above SPLs of 117 dB re 1 µPa (RMS) for the Ace Aquatec ADD. At exposure levels of 139 ± 2 dB re 1 μPa, the animal exhibited strong avoidance behaviour. Strong deterring effects were observed at sensation levels of 84 dB for the Ace Aquatec device. | Kastelein et al., 2015a | |
| Harbour Porpoise | Noise Modelling | A review of behavioural response studies involving porpoise and ADDs. The study used acoustic propagation calculations, the sound properties of the device in question, and the behavioural response thresholds reported in the reviewed studies to estimate deterrence ranges. Using the minimum behavioural response threshold reported in Kastelein et al. (2015a; 117 dB re 1 µPa (RMS)) for the Ace Aquatec ADD, Hermannsen et al. predicted this RL could be experienced by porpoises at distances of up to 4 km. The threshold for the strong avoidance behaviour reported by Kastelein et al. (139 dB re 1 µPa) corresponded to distances between 380-590 m. | Hermannsen et al., 2015 | |
| Airmar 'Unknown' | Harbour Porpoise | Field Study | Northridge et al. (2010) used PAM to study the short-term effects of an Airmar ADD on porpoise density around finfish farms on the west coast of Scotland. Data suggested no significant difference in detection rates across all distances (200 m to 8 km) from ADDs. Porpoises were also detected feeding at distance of 200 m from an active device. However, detection rates were significantly reduced at the four sites closest to an ADD (all within 1 km). Some click trains were still detected at all sites when ADDs were active, including those closest to the sound source, demonstrating partial rather than complete exclusion of porpoises from the affected areas. Detection rates recovered as soon as ADDs were turned off. In the same study, further analysis of broader scale PAM data was used to examine the long term effects of ADD introduction on the west coast of Scotland over two years. This analysis reported that porpoise detections were considerably lower in years when ADDs were active. No porpoise were detected within 4.3 km from an ADD. At other sites, porpoise were detected within 1-2 km of the active ADDs. However, subsequent predictive habitat modelling did not reveal ADD RL as a significant predictor of harbour porpoise distribution | Northridge et al., 2010 |
| Harbour Porpoise | Field Study | An experiment in Denmark used two models of ADD to examine the displacement of wild porpoise by both continuous and periodic exposure to ADDs. As this was a fisheries-based study, rather than a number of ADDs concentrated around a small area as seen in aquaculture, 55 ADDs were spread out at 100 m spacing to cover an area of approximately 0.6 km2. The Airmar ADDs emitted a 300 ms signal every 4 s at 10 kHz with a nominal SL of 132 dB re 1 μPa (RMS). There was a 40-75% reduction in porpoise detection rate when the ADD was active. During continuous-exposure, detection rate was reduced by 65% throughout the 28-day trial; effective to 2.5 km but there was no effect between 2.5 and 5 km, suggesting porpoises were displaced out to either 2.5 km or 5 km. There was some evidence of habituation in the periodic exposure trial, with a strong aversive response to the first and second exposures and a weakened response to subsequent exposures. | Kyhn et al., 2015 | |
| Harbour Porpoise | Field Study | Changes in harbour porpoise abundance when exposed to an Airmar ADD was assessed at site in British Columbia, Canada. Abundance reduced by >90% within 3.5 km, with no porpoise sightings within 200 m whilst the device was on (minimum deterrence distance). The local topography meant that 3.5 km was the maximum range at which observations could be made therefore this range may not represent the full extent of effects. There was no sign of habituation or a reduction in the size of effects over the three week duration of the trials. However, sighting rates recovered within a few days of the ADD being switched off. This was with an older version of the device with a SL of 194 dB re 1 µPa @ 1 m (p-p) focussed at 10 kHz, with a pulse duration 1.8 ms, 40 ms intervals, grouped into 2.3 s trains separated by 2.1 s (measured by Haller and Lemon 1994). A subsequent review of the work by Olesuik et al. (2002) by Hermannsen et al. (2015) calculated that at the minimum deterrence range of 200 m, the RL would have been approximately 148 dB re 1 µPa (p-p). | Olesuik et al., 2002 & Hermannsen et al., 2015 | |
| Airmar 'dB Plus II' | Harbour Porpoise | Field Study | The effects on harbour porpoise due to a single Airmar dB II Plus ADD (fundamental frequency of 10 kHz and a SL approximately 180 dB re 1 µPa @ 1 m)) was studied in the Bay of Fundy, Canada. Harbour porpoise abundance reduced by 92% in close vicinity. Closest average approach to the device when on was 991 m compared to 6 m when off. Total exclusion from an area of up to 645 m from the device and significantly fewer sightings within 1.5 km when active. Using the 645 m minimum deterrence distance, noise modelling suggested that porpoises avoided the area when SPLs exceeded 128 dB re 1 µPa (p-p). Using zones of disturbance and discomfort for porpoises reported by Taylor et al. (1997; 130 dB re 1 µPa), Johnston calculated that this RL would be reached with the Airmar ADD at a range of approximately 532 m from the device. | Johnston, 2002 |
| Harbour Porpoise | Noise Modelling | Desk-based noise modelling by Todd et al. (2019) of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal species. The maximum audible range was based on a sea state of 0 and depths of 10-50 m and SLs for the ADDs were based on Lepper et al. (2014). Models suggest the Airmar ADD signal is audible to harbour porpoise between 32-64 km, depending on sea state, and the sounds could potentially reach a behavioural disturbance level (140–180 dB re 1 µPa (RMS)) (Southall et al., 2007) within a radius of 1.3 km. | Todd et al., 2019 | |
| GenusWave 'Unknown' | Harbour Porpoise | Field Study | Field trials were carried out at a fish farm on the west coast of Scotland with the GenusWave ADD (SL: 176–179 dB re 1 µPa @ 1 m (RMS)). There was no significant effect of sound exposure on the number of harbour porpoise surfacings observed within 200 m from the closest ADD and porpoise abundance remained unaffected. At 20 m, none of the 1/3 octave bands exceeded the hearing threshold of a porpoise by more than 72 dB re 1 µPa (typically insufficient for eliciting significant startle responses in mammals). | Gotz & Janik, 2016 |
| Lofitech 'Seal Scrammer' | Harbour Porpoise | Field Study | In the German Bight in the North Sea, bubble curtains (to reduce sound levels) and ADDs were used to mitigate the impact on harbour porpoise of pile driving noise during construction of a wind farm. A Lofitech ADD (0.5 s pure tone pulses at about 14 kHz and a SL of approximately 189 dB re 1 µPa @ 1 m). By monitoring porpoise echolocation activity, the ADD was shown to have deterred porpoise out to at least 12 km and possibly out to 18 km. Largest decrease in porpoise echolocation was at the closest range (1.5-3 km) where detections fell to around 0.5% (from baseline levels of 4-6%). Reaction to the ADD was equal to or greater than that predicted from pile driving (with a bubble curtain). | Dahne et al., 2017 |
| Lofitech 'Seal Scarer' | Harbour Porpoise | Captive Study | Playback experiments with captive harbour porpoise estimated the audibility and behavioural response to signals from different ADD types. The effect of different received broadband SPLs were identified; a level that did not cause a behavioural change (91 dB re 1 µPa), a level that caused a small change in the surfacing rate and swimming pattern (121 dB re 1 µPa) and a level that caused the porpoise to swim away from the ADDs (i.e., exhibit displacement) (151 dB re 1 µPa). Depending on sea conditions and based on noise modelling, the Lofitech ADD was expected to be audible to porpoise between 18-91 km and likely to deter porpoises at ranges between 0.2-1.2 km based on porpoise hearing thresholds (stimulus levels resulting in a 50% detection rate). This study demonstrates the specific SPLs that can induce averse behavioural responses in harbour porpoise. | Kastelein et al., 2010 |
| Harbour Porpoise | Captive Study | A captive study investigating the ability of porpoise to hear sounds from different ADDs, including the Lofitech device was carried out. As the mean received SL increased, displacement occurred with higher numbers of surfacings, swimming speed and jumps for the captive porpoise. These behavioural reactions occurred above SLs of 121 dB re µPa (RMS) for the Lofitech ADD. At exposure levels of 151 ± 6 dB re 1 μPa, the animal exhibited strong avoidance behaviour. Strong deterring effects were observed at sensation levels of 96 dB for Lofitech device. | Kastelein et al., 2015a | |
| Harbour Porpoise | Noise Modelling | A review of behavioural response studies involving porpoise and ADDs, summarised where available or modelled where not. The study used acoustic propagation calculations, the sound properties of the device in question and the behavioural response thresholds reported in the reviewed studies to estimate deterrence ranges. Using the minimum behavioural response threshold reported in Kastelein et al. (2015a; 121 dB re 1 µPa (RMS)) for the Lofitech ADD, Hermannsen et al. predicted this received level could be experienced by porpoises at distances of up to 2 km. The threshold for the strong avoidance behaviour reported by Kastelein et al. (151 dB re 1 µPa) corresponded to distances between 40-150 m. | Hermannsen et al., 2015 | |
| Lofitech 'Unknown' | Harbour Porpoise | Field Study | A study in the German North Sea used PAM and aerial surveys to study deterrence effects of a Lofitech seal scarer (SL: 189 dB re 1 µPa) on harbour porpoise. Significant deterrence effect on harbour porpoise was reported out to 7.5 km, with likely deterrence effect beyond this distance that could not detected due to the sampling methodology (no PAM recorders were placed beyond this distance). RLs at the deterrence distance of 7.5 km were estimated to be 113 dB re 1 µPa. At a distance of 750 m from the ADD, porpoise activity decreased significantly with 92%, whereas at 0 m no porpoises were detected. These results indicate that all porpoises were deterred from an area of 350 m around the ADD (estimated RL: 146 dB re 1 μPa), while no clicks were detected at 1.5 km recorder indicating that most animals were deterred from an area of approximately 1.9 km around the ADD. | Brandt et al., 2012 |
| Harbour Porpoise | Field Study | A further study was carried out by Brandt et al. (2013) to investigate the zone of reaction for porpoises exposed to Lofitech ADD sounds in Denmark using land-based observers. Clear deterrence effect (100% displacement) were observed up to 1.9 km, with deterrence 50% of the time between 2.1 to 2.4 km. There was a clear reduction in sighting rates within a 1 km radius around the ADD (relating to a minimal RL of ~129 dB re 1 μPa RMS) and in most cases porpoises immediately disappeared when exposed to the ADD at distances of 300 to 1100 m (relating to RLs between 128 and 143 dB re 1 μPa (RMS)). Closest observed porpoise to device was 798 m (RL - 132 dB re 1 μPa (RMS)) and the furthest avoidance reaction was recorded at 2.4 km (RL - 119 dB re 1 μPa (RMS) at the porpoises' location). However, this study had quite low sample sizes. | Brandt et al., 2013 | |
| Harbour Porpoise | Field Study | In the Moray Firth, during the initial construction phase of the Beatrice offshore wind farm, an integrated study was carried out to evaluate mitigation strategies for marine mammals from impact pile driving activities. A PAM array was installed to measure the acoustic output of the construction work and ADDs, and to measure the responses of harbour porpoises to these sounds. Lofitech ADDs were used, with a measured SPL of 187.2 dB re 1 µPa @ 1 m (p-p) at an observed peak frequency of 12,840 Hz. The study reported a strong behavioural response and far-field disturbance from the Lofitech ADD, with porpoise detections decreasing along a gradient of ADD exposure following a 15 minute exposure period. The length of time that it took animals to return to exposed areas following ADD use was determined from the time elapsed between the end of the ADD exposure and the time of the first porpoise detection. There was ≥50% chance of detecting harbour porpoises in the 3 hour period following the ADD playback at distances up to 21.7 km from the ADD, in the 6 hour period this was reduced to distances up to 13.8 km and in the 12 hour period this was reduced further, to distances up to 3.9 km. The minimum time to the first porpoise detection within 1 km following 15 min ADD playback was 133 min. | Thompson et al., 2020 | |
| Lofitech 'Simulated signals' | Harbour Porpoise | Field Study | In Denmark, wild harbour porpoises were exposed to simulated ADD sounds that resemble a Lofitech ADD but with a reduced SL (165 dB re 1 µPa p-p); compared with 189 dB re 1 µPa (RMS) of a real Lofitech) to allow closer exposure to visual tracking. The ADD deterred all porpoises to 190 m, and the majority of porpoises within 525 m (corresponding to median RL 98 dB re 1 µPa). There were mixed behavioural reactions between 350 to 525 m. All porpoises avoided the sound source when RLs exceeded 107 dB re 1 µPa. A single animal approached to a distance of 157 m before leaving the area, corresponding to a RL of 107 dB re 1 µPa. | Mikkelsen et al., 2017 |
| Terecos 'DSMS-4' | Harbour Porpoise | Field Study | Field trials of a Terecos device investigated the impact on porpoise activity proximal to a fish farm in Loch Hourn, Scotland. PAM was used to record porpoise echolocation as a proxy for porpoise activity. The study concluded that there was little evidence of any reduction in porpoise activity associated with the Terecos device being on, although the sites where porpoise activity was reduced during active periods were generally those closest to the device. Porpoise activity was reduced by 9.9% at 300 m, 7.4% at 438 m, 4.3% at 855 m and 1.4% at 1169 m. Data suggest only a weak or minimal response in harbour porpoise activity, though this response was proportional to the distance from the device. Sites beyond 1.2 km experienced slightly elevated levels of echolocation when the device was on, potentially suggesting animals were displaced out to this distance. | Northridge et al., 2013 |
| Harbour Porpoise | Noise Modelling | Desk-based noise modelling by Todd et al. (2019) of different types of ADD on the west coast of Scotland estimated audibility ranges for different marine mammal species. The maximum audible range was based on a sea state of 0 and depths of 10-50 m and SLs for the ADDs were based on Lepper et al. 2014. Models suggest the Terecos ADD sound is audible to harbour porpoise between 37-99 km, depending on sea state. | Todd et al., 2019 | |
| Bespoke ADD signals (i.e. not from a specific manufacturer) | Harbour Porpoise | Field Study | In an experimental field study with harbour porpoise, a high frequency test signal was designed using single frequency tonal bursts between 8 – 18 kHz, similar to signals produced by the Airmar, Lofitech and Ace Aquatec devices (the random frequency sequencing and the pulse width and duty cycle of the Ace Aquatec were also adopted). A low frequency test signal was also made up of pulsed continuous wave sinusoidal tonal bursts at one of 11 randomly switching fundamental frequencies between 1 – 2 kHz and frequency intervals at 100 Hz. This signal was designed to produce outputs comparable to those from the Ace Aquatec US3 low frequency variant ADD. The source levels used were lower (up to approximately 170 dB re 1 μPa @ 1 m (RMS)) than manufactured devices. Porpoise detection rates at most moorings were substantially lower during both high frequency and low frequency signal emissions than during silent control periods, suggesting that emission of both signals reduced the probability of porpoise detections. No significant differences in porpoise detection rates could be demonstrated between low frequency and high frequency signals. | Benjamins et al., 2018 |
| Device | Species | Study Type | Study Summary | Reference(s) |
|---|---|---|---|---|
| Lofitech 'Seal Scarer' | Minke Whale | Field Study | During controlled exposure experiments on minke whales in Iceland, the acoustic properties of a Lofitech ADD were characterised in the field and noise modelling was undertaken to compare the acoustic output of the device with known thresholds for TTS (in this case, those estimated by NMFS, 2016). The model incorporated conservative swim away speeds of 2.5 ms-1 and an ADD deployment duration of 30 minutes. The SL was measured as 198 dB re 1 μPa @ 1 m (RMS) which is below the thresholds of 213 dB re 1 μPa (0-p) for low frequency cetaceans TTS. SEL were also modelled, with the threshold for a cumulative dose at 179 dB re 1 μPa2s and for starting distances of 500 m, 100 m, and 25 m from the ADD, there was no exceedance of the TTS threshold for minke whales. This modelling work suggests that even at extremely close distances (25 m), there is no realistic risk of TTS to minke whales from a Lofitech ADD. | McGarry et al., 2017 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory TTS SEL thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the species hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of an Ace Aquatec device was used to estimate impact zones and corresponding durations to achieve TTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on a total of three ADDs with a SL of 193 dB re 1 µPa at 10 kHz (RMS) and a 30% duty cycle; the TTS threshold would be reached after 2 mins 37 s at 2.5 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same duration but at a distance of 748 m, for killer whales using the SELsens criteria. This could be extended to 7 mins 52 s at 2.5 m / 748 m if switching to a 10% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve TTS with bottlenose dolphins would occur within an impact zone of 175 m. | Götz & Janik, 2013 |
| Airmar 'dB Plus' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used either auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of an Airmar device was used to estimate impact zones and corresponding durations to achieve TTS for bottlenose dolphins and killer whales. For the nominal SPL of 198 dB re 1 µPa, using impact criteria reported by Southall et al. (2007), and with calculations based on a total of 4 ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached after 45 s at 2.5 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same duration but at a distance of 748 m for killer whales using the SELsens criteria. This could be extended to 3 mins at 2.5 m / 748 m if switching to one ADD and a 50% duty cycle. However, calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with 4 ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached after 3 mins (at 2.5 m for bottlenose dolphins and 748 m for killer whales). This could be extended to 11 mins 49 s, if using just one ADD and switching to a 50% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve TTS with bottlenose dolphins would occur within an impact zone of 175 m. | Götz & Janik, 2013 |
| Airmar 'dB Plus II' | Bottlenose Dolphin & Beluga | Noise Modelling | Calculations estimating theoretical risk of TTS induced by an ADD were reported by Gordon and Northridge, using older criteria for TTS in bottlenose dolphins and belugas (Schlundt et al., 2000) with a 1 s tone of 192 dB re 1 µPa. The Airmar signal consists of 32 18.5 ms pulses equal to a single transmission of 592 ms. Thus at the specified output level for an Airmar dB Plus II (194 dB re 1 µPa @ 1 m) a similar degree of TTS would be expected after exposure to a single transmission at a SL of 194 dB re 1 µPa at ranges of 1 m or less. | Gordon & Northridge, 2002 |
| Lofitech 'Universal / Seal Scarer' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used either auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of a Lofitech device was used to estimate impact zones and corresponding durations to achieve TTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on a 25% duty cycle; the TTS threshold would be reached after 8 mins 45 s at 2.5 m (SEL: 203 dB re 1 μPa2 s) for bottlenose dolphins, and for the same duration but at a distance of 748 m for killer whales using the SELsens criteria. This could be extended to 17 mins 29 s at 2.5 m / 748 m if switching to a 12% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve TTS with bottlenose dolphins would occur within an impact zone of 175 m. | Götz & Janik, 2013 |
| Terecos 'DSMS-4' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used either auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of a Terecos device was used to estimate impact zones and corresponding durations to achieve TTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on an array of 3 ADDs and 33% duty cycle; the TTS threshold would be reached after 15 mins 58s at 2.5 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same duration but at a distance of 748 m, for killer whales using the SELsens criteria. This could be extended to 47 mins 55 s at 2.5 m / 784 m if switching to just one ADD and an 11% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve TTS with bottlenose dolphins would occur within an impact zone of 175 m. | Götz & Janik, 2013 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Ace Aquatec device to estimate impact zones and corresponding durations to achieve TTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of 3 ADDs and a 30% duty cycle; the TTS threshold would be reached after 2 mins 37s at 89 m (SEL: 203 dB re 1 μPa2s). This could be extended to 7 mins 52 s at 89 m if switching to one ADD and a 10% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve TTS would occur within an impact zone of 345 m. | Götz & Janik, 2013 |
| Airmar 'dB Plus' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Airmar device to estimate impact zones and corresponding durations to achieve TTS for a porpoise. For the nominal SL of 198 dB re 1 µPa, and using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of 4 ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached after 45 s at 89 m (SEL: 203 dB re 1 μPa2 s). This could be extended to 3 mins at 89 m if using just one ADD and switching to a 50% duty cycle. However calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with 4 ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached after 3 mins at 89 m, and could be extended to 11 mins 49 s if using just one ADD and switching to a 50% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve TTS would occur within an impact zones of 345 m. | Götz & Janik, 2013 |
| GenusWave 'Unknown' | Harbour Porpoise | Noise Modelling | Porpoises exposed to 1.5 kHz pure tones developed significant TTS at a SEL of 190 dB re 1 µPa2s (Kastelein et al. 2013). Therefore the risk of TTS for porpoise from the GenusWave device would be extremely low. They would only be affected when exposed to 50 pulses within one meter of the loudspeaker. Given the duty cycle of 0.8%, this means that an animal would have to stay within 1 m of the loudspeaker for almost 21 min. Alternatively, an animal would receive the same noise dose if it was exposed to the equivalent of 4000 s of continuous noise within 20 m of the loudspeaker. Taking the duty cycle and pulse duration into account, such an exposure would only be reached after 5 to 6 days of continuous presence within 20 m, representing a highly unrealistic scenario and therefore suggesting a low risk of TTS. | Götz & Janik, 2015 |
| Lofitech 'Universal / Seal Scarer' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Lofitech device to estimate impact zones and corresponding durations to achieve TTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a 25% duty cycle; the TTS threshold would be reached after 8 mins 24 s at 89 m (SEL: 203 dB re 1 μPa2 s). This could be extended to 17 mins 29 s at 89 m if switching to a 12% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve TTS would occur within an impact zone of 345 m. | Götz & Janik, 2013 |
| Lofitech 'Simulated signals' | Harbour Porpoise | Captive Study | A captive harbour porpoise was exposed to an artificial ADD signal with a peak frequency of 14 kHz. A significant TTS was found, measured by auditory evoked potentials, with an onset of 142 dB re 1 μPa2s at 20 kHz and 147 dB re 1 μPa2s at 28 kHz. Single ADD signals with a (SL) of 193 dB re 1 μPa @ 1 m are assumed to induce a TTS in harbour porpoises up to distances between 211 m (spherical spreading in deep water) and 5.9 km (cylindrical spreading in shallow water), depending on theoretical sound propagation. | Schaffeld et al., 2019 |
| Terecos 'DSMS-4' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Terecos device to estimate impact zones and corresponding durations to achieve TTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of 3 ADDs and a 33% duty cycle; the TTS threshold would be reached after 15 mins 58 s at 89 m (SEL: 203 dB re 1 μPa2s). This could be extended to 47 mins 55 s at 89 m if switching to an 11% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve TTS would occur within an impact zone of 345 m. | Götz & Janik, 2013 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Ace Aquatec device to estimate impact zones and corresponding durations to achieve TTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on a total of three ADDs and a 33% duty cycle; the TTS threshold would be reached after 2 mins 37 s at 10 m (SEL: 203 dB re 1 μPa2 s). This could be extended to 7 mins 52 s at 10 m if switched to one ADD and a 11% duty cycle. | Götz & Janik, 2013 |
| Airmar 'dB Plus' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Airmar device to estimate impact zones and corresponding durations to achieve TTS for a harbour seal. For the nominal sound pressure level of 198 dB re 1 µPa, using impact criteria reported by Southall et al. (2007), and with calculations based on a total of four ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached after 45 s at 10 m (SEL: 203 dB re 1 μPa2 s). This could be extended to 3 mins at 10 m if switched to one ADD and a 11% duty cycle. However, calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with four ADDs each with a 50% duty cycle (total duty cycle = 200%); the TTS threshold would be reached in 3 mins, with this being extended to 11 mins 49 s if just once ADD and a duty cycle of 50% was used. | Götz & Janik, 2013 |
| Airmar 'dB Plus II' | Harbour Seal | Noise Modelling | Calculations estimating theoretical risk of TTS induced by an ADD were reported by Gordon and Northridge, using older criteria for TTS in bottlenose dolphins and belugas (Schlundt et al., 2000) with a 1 s tone of 192 dB re 1 µPa. Hearing thresholds for harbour seals are more than 10 dB higher than those of bottlenose dolphins, giving extrapolated instantaneous TTS thresholds for common seals of 204 dB re 1 µPa @1 m for an Airmar transmission. This value is above the devices SLs. The Airmar transmission consists of 32, 18.5 ms pulses equal to a single transmission of 592 ms. | Gordon & Northridge 2002 |
| GenusWave 'Unknown' | Harbour Seal | Noise Modelling | No empirical measurements, but calculations based on the acoustic output of the GenusWave device demonstrate low realistic risk of TTS. The onset of a TTS occurs at SEL of ~182 dB re 1 µPa2s. The SEL of a single 0.2 s pulse is 173 dB re 1 µPa2s and the cumulative SEL of 5 pulses is 180 dB re 1 µPa2s. Therefore, even if a harbour seal was exposed to five pulses at a distance of 1 m from the loudspeaker; it would not be at risk of TTS. | Götz & Janik, 2015 |
| Lofitech 'Universal / Seal Scarer' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Lofitech device to estimate impact zones and corresponding durations to achieve TTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on a 25% duty cycle; the TTS threshold would be reached after 8 min 24 s at 10 m (SEL: 203 dB re 1 μPa2s). This could be extended to 17 mins 29 s at 10 m if switching to a 12% duty cycle. | Götz & Janik, 2013 |
| Terecos 'DSMS-4' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Terecos device to estimate impact zones and corresponding durations to achieve TTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on an array of 3 ADDs and 33% duty cycle; the TTS threshold would be reached after 15 min 58 s at 10 m (SEL: 203 dB re 1 μPa2s). This could be extended to 47 mins 55 s at 10 m if switching to one ADD and an 11% duty cycle. | Götz & Janik, 2013 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Lofitech 'Seal Scarer' | Field Study | Minke Whale | During CEE in Iceland with minke whales, the acoustic properties of a Lofitech ADD were characterised in the field and noise modelling was undertaken to compare the acoustic output of the device with known thresholds for PTS (in this case, those estimated by NMFS, 2016). The model incorporated conservative swim away speeds of 2.5 ms-1 and an ADD deployment duration of 30 minutes. The source peak SPL was measured as 204 dB re 1 μPa @1 m which is below the thresholds of 219 dB re 1 μPa (0-p) for instantaneous PTS (NMFS, 2016). SEL was also modelled, with the threshold of 199 dB re 1 μPa2s and for starting distances of 500 m, 100 m, and 25 m from the ADD, there was no exceedance of the SEL PTS threshold for minke whales. This modelling work suggests that even at extremely close distances (25 m), there is no realistic risk of PTS injury to minke whales from a Lofitech ADD. | McGarry et al., 2017 |
| Device | Study Type | Species | Study Summary | Reference |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used both auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of an Ace Aquatec device was used to estimate impact zones and corresponding durations to achieve PTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on a total of three ADDs and a 30% duty cycle; the PTS threshold would be reached after 3 hours 10 min at 15 m (SEL: 221.6 dB re 1 μPa2s) or after 2 mins 37 s at 2 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same durations but at distances of 642 m and 79 m, respectively, for killer whales using the SELsens criteria. This could be extended to 9 hours 30 mins at 15 m / 642 m and 3 mins at 2 m / 79 m if switching to a 10% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve PTS with bottlenose dolphins would occur within impact zones of 150 m and 18 m, respectively. | Götz & Janik, 2013 |
| Airmar 'dB Plus' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used either auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of an Airmar device was used to estimate impact zones and corresponding durations to achieve PTS for bottlenose dolphins and killer whales. For the nominal SPL of 198 dB re 1 µPa, using impact criteria reported by Southall et al. (2007), and with calculations based on a total of four ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 55 min at 15 m (SEL: 221.6 dB re 1 μPa2s) or after 45 s at 2 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same durations but at distances of 642 m and 79 m, respectively, for killer whales using the SELsens criteria. This could be extended to 3 hours 38 mins at 15 m / 642 m and 3 mins at 2 m / 79 m if switching to one ADD and a 50% duty cycle. However, calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with four ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 3 hours 37 mins at (at 15 m bottlenose dolphins and 642 m for killer whales), or 3 mins (at 2 m for bottlenose dolphins and 79 m for killer whales), depending on the impact zone chosen. This could be extended to 14 hours 29 mins and 11 mins 49 s, respectively, if using just one ADD and switching to a 50% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve PTS with bottlenose dolphins would occur within impact zones of 150 m and 18 m, respectively. | Götz & Janik, 2013 |
| Lofitech 'Universal / Seal Scarer' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of a Lofitech device was used to estimate impact zones and corresponding durations to achieve PTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on a 25% duty cycle; the PTS threshold would be reached after 10 hours 8 min at 15 m (SEL: 221.6 dB re 1 μPa2s) or after 8 mins 45 s at 2 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same durations but at distances of 642 m and 79 m, respectively, for killer whales using the SELsens criteria. This could be extended to 21 hours 7 mins at 15 m / 642 m and 17 mins 29 s at 2 m / 79 m if switching to a 12% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve PTS with bottlenose dolphins would occur within impact zones of 150 m and 18 m, respectively. | Götz & Janik, 2013 |
| Terecos 'DSMS-4' | Killer Whale & Bottlenose Dolphin | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used either auditory thresholds reported by Southall et al. (2007) or a more conservative approach suggested by the authors that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens). The known acoustic output of a Terecos device was used to estimate impact zones and corresponding durations to achieve PTS for bottlenose dolphins and killer whales. Using impact criteria reported by Southall et al. (2007), and with calculations based on an array of three ADDs and 33% duty cycle; the PTS threshold would be reached after 19 hours 17 min at 15 m (SEL: 221.6 dB re 1 μPa2s) or after 15 mins 58 s at 2 m (SEL: 203 dB re 1 μPa2s) for bottlenose dolphins, and for the same durations but at distances of 642 m and 79 m, respectively, for killer whales using the SELsens criteria. This could be extended to 57 hours 51 mins at 15 m / 642 m and 47 mins 55 s at 2 m / 79 m if switching to just one ADD and an 11% duty cycle. Using the more conservative SELsens criteria, the previously mentioned exposure durations to achieve PTS with bottlenose dolphins would occur within impact zones of 150 m and 18 m, respectively. | Götz & Janik, 2013 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent Scrammer' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Ace Aquatec device to estimate impact zones and corresponding durations to achieve PTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of three ADDs and a 30% duty cycle; the PTS threshold would be reached after 3 hours 10 min at 76 m (SEL: 221.6 dB re 1 μPa2s) or after 2 mins 37 s at 9 m (SEL: 203 dB re 1 μPa2s). This could be extended to 9 hours 30 mins at 76 m and 3 mins at 9 m if switching to one ADD and a 10% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test species' hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve PTS would occur within impact zones of 295 m and 35 m, respectively. | Götz & Janik, 2013 |
| Ace-Aquatec 'Silent / Universal Scrammer' | Harbour Porpoise | Noise Modelling | Acoustic sensitivity modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. For an Ace Aquatec ADD, the PTS SEL threshold for a porpoise would be exceeded after 8 hours at 500 m from a single device for a very conservative scenario of a stationary animal. | Lepper et al., 2014 |
| Airmar 'dB Plus' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Airmar device to estimate impact zones and corresponding durations to achieve PTS for a porpoise. For the nominal sound pressure level of 198 dB re 1 µPa, and using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of four ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 55 mins at 76 m (SEL: 221.6 dB re 1 μPa2s) or after 45 s at 9 m (SEL: 203 dB re 1 μPa2s). This could be extended to 3 hours 38 mins at 76 m and 3 mins at 9 m if using just one ADD and switching to a 50% duty cycle. However, calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with 4 ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 3 hours 37 mins at 76 m or after 3 mins at 9 m. This could be extended to 14 hours 29 mins at 76 m and 11 mins 49 s at 9 m if using just one ADD and switching to a 50% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve PTS SEL would occur within impact zones of 295 m and 35 m, respectively. | Götz & Janik, 2013 |
| Airmar 'dB Plus II' | Harbour Porpoise | Noise Modelling | Acoustic sensitivity modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. According to calculations presented in Lepper et al. (2014) the PTS threshold would be exceeded after 5.5 hours at 500 m (single device); 2.75 hours at 500 m (two devices); 1.8 hours at 500 m (three devices). However, by reducing the duty cycle from 50% to 2% the PTS SEL injury criteria for a porpoise would not be exceeded even at distances greater than 300 m over a 24 hour period. The animal movement in these calculations is very conservative, a stationary animal remains at source over the exposure. | Lepper et al., 2014 |
| GenusWave 'Unknown' | Harbour Porpoise | Noise Modelling | The authors reported an extremely low risk of TTS for porpoise, whereby animals would only be affected if exposed to 50 pulses within 1 m of the loudspeaker. Given the duty cycle of 0.8%, this means that an animal would have to stay within 1 m of the loudspeaker for almost 21 min. Alternatively, an animal would receive the same noise dose if it was exposed to the equivalent of 4000 s of continuous noise within 20 m of the loudspeaker. Taking the duty cycle and pulse duration into account, such an exposure would only be reached after 5 to 6 days of continuous presence within 20 m, representing a highly unrealistic scenario and therefore suggesting a low risk of SEL TTS and therefore, and even lower risk of SEL PTS. | Götz & Janik, 2015 |
| Lofitech 'Universal / Seal Scarer' | Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Lofitech device to estimate impact zones and corresponding durations to achieve PTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a 25% duty cycle; the PTS threshold would be reached after 10 hours 8 min at 76 m (SEL: 221.6 dB re 1 μPa2s) or after 8 mins 24s at 9 m (SEL: 203 dB re 1 μPa2s). This could be extended to 21 hours 7 mins at 76 m and 17 mins 29 s at 9 m if switching to a 12% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SEL to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve PTS would occur within impact zones of 295 m and 35 m, respectively. | Götz & Janik, 2013 |
| Terecos 'DSMS-4' | Harbour Porpoise | Noise Modelling | Underwater noise modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. For a porpoise, the threshold at 100 m would be exceeded after about 2.5 hours and the safe range for 24 hour exposure was beyond 500 m based on a 6.7% duty cycle (worst case scenario). Other programmes (duty cycle to 1.3% using a 200 ms pulse every 15 s) would increase time before an injury threshold was reached at a fixed distance. In the case of a harbour porpoise for a sandy seabed the injury threshold would be reached in less than 24 hours for ranges less than 200 m at the lower duty cycle compared to greater than 500 m at the higher duty cycle. The animal movement in these calculations is very conservative, a stationary animal remains at source over the exposure. | Lepper et al., 2014 |
| Harbour Porpoise | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Terecos device to estimate impact zones and corresponding durations to achieve PTS for a porpoise. Using impact criteria reported by Lucke et al. (2009), and with calculations based on a total of three ADDs and a 33% duty cycle; the PTS threshold would be reached after 19 hours 17 min at 76 m (SEL: 221.6 dB re 1 μPa2s) or after 15 mins 58 s at 9 m (SEL: 203 dB re 1 μPa2s). This could be extended to 57 hours 51 mins at 76 m and 47 mins 55 s at 9 m if switching to an 11% duty cycle. Using a more conservative approach suggested by Götz and Janik that references SELs to the test subject's hearing threshold (sound exposure sensation level, SELsens), the previously mentioned exposure durations to achieve PTS would occur within impact zones of 295 m and 35 m, respectively. | Götz & Janik, 2013 |
| Device | Study Type | Species | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Silent / Universal Scrammer' | Grey Seal & Harbour Seal | Noise Modelling | Acoustic sensitivity modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. For an Ace Aquatec ADD, the injury threshold for a seal at 100 m would be exceeded after around 3 hours and the threshold range for 24 hour exposure is around 350 m (worst case scenario duty cycle based on manufactures information of 72, 5 s bursts per hour; 10%). The system allows programming of lower numbers of burst per hour lowering this duty cycle and therefore increasing time for reaching an injury threshold at a fixed distance. The animal movement in these calculations is very conservative, a stationary animal remains at source over the exposure. | Lepper et al., 2014 |
| Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Ace Aquatec device to estimate impact zones and corresponding durations to achieve PTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on a total of three ADDs and a 33% duty cycle; the PTS threshold would be reached after 19 hours 17 min at 60 m (SEL: 221.6 dB re 1 μPa2s) or after 15 mins 58 s at 7 m (SEL: 203 dB re 1 μPa2s). This could be extended to 57 hours 51 mins at 60 m and 47 mins at 7 m if switching to an 11% duty cycle. | Götz & Janik, 2013 | |
| Airmar 'dB Plus' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of an Airmar device to estimate impact zones and corresponding durations to achieve PTS for a harbour seal. For the nominal sound pressure level of 198 dB re 1 µPa, and using impact criteria reported by Southall et al. (2007), and with calculations based on a total of four ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 55 min at 60 m (SEL: 221.6 dB re 1 μPa2s) or after 45 s at 7 m (SEL: 203 dB re 1 μPa2s). This could be extended to 3 hours 38 mins at 60 m and 3 mins at 7 m if switching to one ADD and a 50% duty cycle. However calculations using a lower measured sound pressure level for the Airmar device (192 dB re 1 µPa), with four ADDs each with a 50% duty cycle (total duty cycle = 200%); the PTS threshold would be reached after 3 hours 37 mins at 60 m or after 3 mins at 7 m. This could be extended to 14 hours 29 mins at 60 m and 11 mins 49 s at 7 m if using just one ADD and switching to a 50% duty cycle. | Götz & Janik, 2013 |
| Airmar 'dB Plus II' | Grey Seal & Harbour Seal | Noise Modelling | Acoustic sensitivity modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. For an Airmar ADD, a seal at 100 m would exceed the threshold after about 3.3 hours for a single device with time decreasing pro rata to 1.6 and 1.1 hours when two and three devices were operational at the site. With single device animals remaining at 400 m for 24 hours would reach the threshold for injury. The animal movement in these calculations is very conservative, a stationary animal remains at source over the exposure. | Lepper et al., 2014 |
| GenusWave 'Unknown' | Harbour Seal | Noise Modelling | No empirical measurements, but calculations based on the acoustic output of the GenusWave device demonstrate low realistic risk of hearing damage. The onset of a temporary threshold shift occurs at sound exposure levels (SEL) of ~182 dB re 1 µPa2s. The SEL of a single 0.2 s pulse is 173 dB re 1 µPa2s and the cumulative SEL of 5 pulses is 180 dB re 1 µPa2s. Even if a harbour seal was exposed to five pulses at a distance of 1 m from the loudspeaker; it would not be at risk of TTS, therefore the risk of PTS from the device is even lower. | Götz & Janik, 2015 |
| Lofitech 'Universal / Seal Scarer' | Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Lofitech device to estimate impact zones and corresponding durations to achieve PTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on a 25% duty cycle; the PTS threshold would be reached after 10 hours 8 min at 60 m (SEL: 221.6 dB re 1 μPa2s) or after 8 mins 24s at 7 m (SEL: 203 dB re 1 μPa2s). This could be extended to 21 hours 7 mins at 60 m and 17 mins and 29 s at 7 m if switching to a 12% duty cycle. | Götz & Janik, 2013 |
| Terecos 'DSMS-4' | Grey Seal & Harbour Seal | Noise Modelling | Acoustic sensitivity modelling by Lepper et al. (2014) predicted injury thresholds for different marine mammal species based on the output of various models of commercially available ADD. For a Terecos ADD, the seal injury threshold would be exceeded if seal remained within 100 m of device for 9 hours, or 24 hours within 200 m. The animal movement in these calculations is very conservative, a stationary animal remains at source over the exposure. | Lepper et al., 2014 |
| Harbour Seal | Noise Modelling | A review of the effectiveness and potential impacts on marine mammals of a selection of ADDs was carried out by Götz and Janik (2013). In this paper, they used auditory thresholds and the known acoustic output of a Terecos device to estimate impact zones and corresponding durations to achieve PTS for a harbour seal. Using impact criteria reported by Southall et al. (2007), and with calculations based on a total of three ADDs and a 33% duty cycle; the PTS threshold would be reached after 19 hours 17 min at 60 m (SEL: 221.6 dB re 1 μPa2s) or after 15 mins 58 s at 7 m (SEL: 203 dB re 1 μPa2s). This could be extended to 57 hours 51 mins at 60 m and 47 mins at 7 m if switching to an 11% duty cycle. | Götz & Janik, 2013 |
Table A2‑2: Summary of studies investigating and/or documenting efficacy of specific ADDs on pinnipeds. Studies are detailed by manufacturer and device type (based on the name provided in the study), the species assessed, and a definition of the study type (e.g. field study or noise modelling). A summary of the study is provided; these summaries are not presented as a critical review of the work, but are to provide a brief overview of the experimental design, findings and/or conclusions of the author(s) where relevant to the context of this report
| Device | Species | Use | Study Summary | Reference(s) |
|---|---|---|---|---|
| Ace-Aquatec 'Seal Scrammer' | Harbour Seal | Captive Study | Playback experiments with captive harbour seal estimated the audibility and behavioural response to signals from different types of ADD. The effect of different received broadband sound pressure levels were measured; a level which did not cause a behavioural change (109 dB re 1 µPa), a level which caused the seal to haul out very occasionally (124 dB re 1 µPa) and a level which caused the seal to haul out approximately 10% of the time (134 dB re 1 µPa). Depending on sea conditions and based on noise modelling, the Ace Aquatec ADD was expected to be audible to seals between 14-91 km and likely to deter seals at ranges between 0.2-4.1 km based on harbour seal hearing thresholds (stimulus levels resulting in a 50% detection rate). | Kastelein et al., 2010 |
| Harbour Seal | Captive Study | Captive harbour seals were exposed to playback signals from two models of ADD. Two captive seals responded to the playback of Ace Aquatec sounds by raising their heads (and ears) from the water to some extent, perhaps to avoid the sound. One of the seals also hauled out. Effects on the seals' behaviour were quantified at three SPLs: one which did not cause behavioural changes (109 dB re 1 µPa (RMS)), one which caused one of the seals to haul out occasionally (124 dB re 1 µPa (RMS)), and one which caused one of the seals to haul out more than 10% of the time (134 dB re 1 µPa (RMS)). The seals hauled out more and spent more time with their heads above water as SPLs increased. | Kastelein et al., 2015b | |
| Ace-Aquatec 'Unknown' | Grey Seal & Harbour Seal | Captive Study & Field Study | Playback experiments with both grey and harbour seals were carried out in captivity and in the wild, with different sound sources including four models of ADD (but with lower SLs). In captivity, food motivation was introduced and mean RLs for all sounds in the pool ranged from 142-147 dB re 1 µPa (RMS). Playback experiments in the wild used broadband SLs of 172 dB re 1 µPa (RMS). A single emission of sounds in the field experiment (10 s burst) would result in a SEL of 182 dB re. 1 µPa2s and a single emission (6 s) in the captive trials would amount to a SEL of 156 dB re 1 μPa2s. In captivity with food motivation, seals did not respond differently to the different sound types and habituation in both grey and harbour seals occurred at RL of 146 dB re 1 μPa (RMS). In the wild, for signals resembling that of an Ace Aquatec ADD (but with a lower SL), the deterrence range was 60 m with an avoidance threshold of 138 dB re 1 µPa. | Götz & Janik, 2010 |
| Airmar 'dB Plus' | Grey Seal & Harbour Seal | Captive Study & Field Study | Playback experiments with both grey and harbour seals were carried out in captivity and in the wild, with different sound sources including four types of ADD. In captivity, food motivation was introduced and mean received sound levels (RMS) for all ADDs in the pool ranged from 142-147 dB re 1 µPa. Playback experiments in the wild used broadband SLs of 172 dB re 1 µPa (RMS). A single emission of sounds in the field experiment (10 s burst) would result in a SEL of 182 dB re. 1 µPa2s and a single emission (6 s) in the captive trials would amount to a SEL of 156 dB re 1 µPa2s. In captivity with food motivation, seals did not respond differently to the different sound types and habituation in both grey and harbour seals occurred at RL of 146 dB re 1 μPa (RMS). In the wild, for signals resembling that of an Airmar ADD (but with a lower SL), the deterrence range was 40 m with an avoidance threshold of 144 dB re 1 µPa (RMS). | Götz & Janik, 2010 |
| Harbour Seal | Noise Modelling | In situ measurements of the sound fields of an Airmar ADD were made in the Bay of Fundy, Canada and were compared with hearing thresholds of harbour seals. With a SL of 195 dB re 1 µPa @ 1 m with 10 kHz pulses, 1.8 ms duration every 40 ms for 2.5 sec, it was predicted with noise modelling that the device could be clearly audible to harbour seals up to 2.9 km depending on ambient noise. Based on the average sea states experienced in the Bay of Fundy, over half of the time conditions would result in an audible range of approximately 2.1 km, with the highest ambient noise levels reducing this further to 1.4 km (approximately 5% of the time). | Terhune et al., 2002 | |
| Harbour Seal | Field Study (Aquaculture) | Behavioural response studies in the Bay of Fundy in Canada investigated the reactions of harbour seals to signals from an Airmar ADD around an aquaculture site (but with an array of four ADDs and SL of 172 dB re 1 µPa; 23 dB lower than the maximum operating SL at 195 dB re 1 µPa @ 1 m.). SPLs at 1, 5 and 10 m water depths within the aquaculture cage sites were generally <162 dB re 1 µPa. ADD sounds were predicted through modelling to be audible to harbour seals at ranges of 1.1-20.2 km, depending on the ambient noise levels. Results showed that harbour seals familiar with the Airmar dB Plus II ADD signal showed no behavioural response when switched on; one individual approached within 45 m of the device and seals passed close by to reach a haul-out site. However, the operating SL recorded during the study was lower than the SL stated by the manufacturer. The authors conclude that the ADDs used in the study area were, at the SL recorded, not loud enough to deter the harbour seals, with many seals in the area potentially becoming habituated to the signals. | Jacobs & Terhune, 2002 | |
| South American Sea Lions | Field Study (Aquaculture) | A controlled study of two finfish farms in southern Chile with similar depredation rates by South American sea lions (Otaria flavescens) implemented an ADD at one of the farms for a three month trial period. There were statistically lower levels of predation at the site with the ADD and the site with the ADD experienced significantly less predation than it had done during the same period in the previous year. However, the sample size was small and the period was not long enough to account for any possible habituation. | Vilata et al., 2010 | |
| Harbour Seal | Field Study (Aquaculture) | CEEs to wild seals on the west coast of Scotland using telemetry methods to monitor movement in response to signals from an Airmar device (SL was measured at 195 dB re 1 µPa @ 1 m (RMS)). Typical behavioural changes during responses included restricted area movement, directed movement away from the sound source and diverting of existing movement around the sound source. Over nine CEEs, behavioural responses were observed at ranges up to 1,037 m, with the shortest range at which no response was observed at 653 m. The loudest non-response CEE was estimated at a RL of 138 dB re 1 µPa (RMS) and the quietest responsive CEE was estimated at a RL of 134 dB re 1 µPa (RMS). Though the small sample size for the Airmar (nine CEEs) device makes it difficult to draw firm conclusions, the authors stated there is no evidence to suggest that the Airmar would be more effective for aversive sound mitigation than the Lofitech ADD (which was trialled in this study and was also shown to be an effective deterrent; see the Lofitech section of this table for further information). | Gordon et al., 2015 | |
| Airmar 'Seal-Scarer' | Harbour Seal | Field Study (Salmon River) | Attempts were made in a river in British Columbia, Canada to reduce the depredation of outgoing salmon smolts by harbour seals at night using an Airmar ADD. During short-term field trials, significantly fewer harbour seals fed on outgoing salmon smolts on the seven nights the Airmar device was deployed, compared with seven control nights when no deterrent was used. A mean of 0.4 animals was present during the acoustical tests (range, 0–1) compared with a mean of 8 animals on control nights (range, 0–26). The Airmar ADD prevented seals feeding within a 50 m radius of the ADD (the approximate deterrence range for this study), and displaced seals to a poorer feeding site downstream. However, due to the short period (14 days), no conclusions on long-term efficacy can be drawn. | Yurk & Trites, 2000 |
| FaunaGuard 'Seal Module' | Harbour Seal | Captive Study | A captive experiment with two harbour seals in a pool investigated the behavioural responses to this device, which produces a signal consisting of 16 different sounds played in succession. The signal consisted of sounds between 200 Hz to 20 kHz with random inter-sound intervals of 3-10 s, mean interval 6.5 s, and duty cycle ~60%. The responses were measured at two ambient noise levels, approximately replicating Beaufort Sea State 0 and 4. Results showed that at a mean RL of 142 dB re 1 μPa the background noise from the higher sea state did not affect the behavioural response. Based on increases in jumping behaviour of both seals, the behavioural threshold SPL was reported to be somewhere between 136 and 148 dB re 1 μPa (mean = 142 dB re 1 μPa), with significant changes in the time the seals either held their head out of the water or hauled occurring above 160 dB re 1 μPa. The seals employed differing strategies to avoid the sound above a specific SPL; whilst the responses of both seals involved jumping, one seal held its head out of the water more frequently whereas the other hauled out more frequently. This could demonstrate the variability between individuals in how they choose to respond to averse sounds. The individual effect of each of the 16 sounds was not evaluated, so it is not known which of these induced a greater response. The mean SL of the signal was 182 dB re 1 μPa, and combining this with the behavioural thresholds and sound propagation modelling, the authors estimate the effective deterrent range for the device is between 500-1000 m. | Kastelein et al., 2017 |
| GenusWave 'Unknown' | Grey Seal | Captive Study | Captive exposure experiments with six grey seals to startling band-limited noise pulses 200 ms long with rise and fall times of 5 ms, a peak frequency of 950 Hz spanning approximately 2 octaves and a SL of 170 dB re 1 μPa (RMS) which exceeded the animal's hearing threshold by approximately 100 dB. Five of seven seals showed clear signs of a startle response (flinches) while two did not. In seals that startled, the sound pulse also prevented fish retrieval and increasingly caused an immediate rapid flight response which was followed by an erratic jump out of the pool indicating sensitisation to the ADD signal. An average startle response threshold of 159 dB re 1 μPa reflects a sensation level of approximately 93 dB above the hearing threshold. Once sensitised, seals even avoided a known food source that was close to the sound source. However when exposed to sounds of equal energy as the startle stimulus but with a longer rise time of 100 ms, the flight responses were either not initiated or waned, demonstrating habitation in contrast to the signals with shorter rise times (5 ms) | Götz & Janik, 2011 |
| Harbour Seal | Field Study (Aquaculture) | Field testing of an ADD at finfish farms on the west coast of Scotland. The sound exposure consisted of isolated 200 ms long, 2–3 third octave-band noise pulses with a peak frequency of 1 kHz and a SL of ∼180 dB re 1 µPa (RMS). Significant reduction in the number of seal tracks recorded by land-based observers (91%) within 250 m of the device at a fish farm while the number of seal tracks at greater distances (250-1500 m and >1500 m) remained unaffected. The noise pulse is likely to elicit startle responses at RLs of approximately 145 dB re 1 µPa. Therefore startle responses would be expected to occur at distances of up to 82 m around the ADD. There was no evidence of habituation to the ADD signals over the 43 day study period and no significant effect on harbour porpoise distribution at distances within 250 m of the ADD, 250–1500 m and beyond 1500 m. | Götz & Janik, 2015 | |
| Grey & Harbour Seal | Field Study (Aquaculture) | Long-term field trials with the GenusWave ADD (SL: 176–179 dB re 1 µPa @ 1 m) at a finfish farms in Scotland. The 1/3 octave band analysis at 20 m distance showed that the central band at 1 kHz exceeded the auditory threshold of a seal by 98 dB (sensation level). But visual monitoring showed that the number of seal surfacings within 100 m (modelled RL: 145 dB re 1 µPa) from the loudspeakers was only slightly lower during sound exposure. Modelling suggested a possible reduction in seal surfacings of ~57%, but this was not significant. Sound exposure resulted in 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. The authors reported that predation occurred only in 2 months out of the 12.5 month study period, noting that these two months were early on in the study; concluding that this was therefore unlikely to be due to habituation. | Götz & Janik, 2016 | |
| Lofitech 'Seal Scarer' | Grey & Harbour Seal | Field Study (Salmon River) | Two Lofitech seal scarers (500 ms pulses at 15 kHz with a SL of ~ 189 dB re 1 µPa @ 1 m) were introduced to prevent seals swimming up a river on the northeast coast of Scotland. The use of the ADDs had no significant effect on the absolute abundance of seals in the survey area in either river tested, but it did reduce seal movement upstream significantly, by ∼50% in both rivers (constant over the 4 month trial). Notably during 67% or more of surveys when seals were present and the ADD was operating, seals were observed in close proximity to the device (<200 m). Results suggest that the ADD was partially effective as a barrier to seal movements upstream. The authors note that the effective deterrent range stated by the manufacturer (~300 m) will be considerably less in the noisy environment and shallow topography found in a river. | Graham et al., 2009 |
| Grey & Harbour Seal | Field Study (Salmon Fishery) | Field trials of Lofitech ADD in a salmon bagnet fishery in Scotland. Grey seals were more persistent at this site than harbour seals, both when the ADD was off and on. The number of seal sightings and the time seals spent near a coastal salmon fishery were significantly reduced. Significantly fewer seals were observed when the device was active; in 2009, 19 seals were detected when the ADD was off compared to none when it was on, and in 2010 there were 19 seals detected when off and 6 detected when on. Approximately a third more fish were landed per hour (also significant) during periods where a Lofitech ADD was switched on. Results indicated that the higher fish landings when the ADD was operating were a direct result of the reduction in the number of seals in the vicinity of the net. Seal-damaged fish were only found within the bagnet during off treatments. Some potential habituation was found, with no seals sighted within 80 m of the device in the first year (2009) and 7 sightings the following year, however in both years the ADD significantly reduced the sightings of seals. Overall, the ADD was found to be an effective seal deterrent, however this study had relatively low sample sizes with very few depredating individuals. On 20 occasions when seals were seen with salmon prey, 15 of these occasions were attributed to one individual. | Harris et al., 2014 | |
| Harbour Seal | Field Study | CEEs to wild seals on the west coast of Scotland using telemetry methods to monitor movement in response to signals from two models of ADD (the Lofitech device SL was measured at 193 dB re 1 µPa @ 1 m (RMS). Typical behavioural changes during responses included restricted area movement, directed movement away from the sound source and diverting of existing movement around the sound source. The shortest range for a CEE that did not elicit a response was 998 m (predicted SL 132 dB re 1 µPa (RMS)). The greatest range at which a response was recorded was 3,122 m (predicted RL:120 dB re 1 µPa (RMS)). 100% of CEEs within ~1 km showed a response and the minimum approach distance was 473 m throughout the study. Tolerance ranges were between 225 m to over 2,000 m with the average tolerance range reported at 943 m. This study demonstrates that averse behavioural responses can occur at the scale of multiple kilometres for the Lofitech device. | Gordon et al., 2015 | |
| Harbour Seal | Captive Study | Playback experiments with captive harbour seals estimated the audibility and behavioural response to signals from different types of ADD. The effect of different received broadband SPLs were measured; a level which just did not cause a behavioural change (128 dB re 1 µPa), a level which caused the seal to haul out very occasionally (133 dB re 1 µPa) and a level which caused the seal to haul out approximately 10% of the time (138 dB re 1 µPa). Depending on sea conditions and based on noise modelling, the Lofitech ADD was expected to be audible to seals between 19-99 km and likely to deter seals at ranges between 0.2-4.1 km based on harbour seal hearing thresholds (stimulus levels resulting in a 50% detection rate). | Kastelein et al., 2010 | |
| Harbour Seal | Captive Study | Captive harbour seals were exposed to playback signals from two models of ADD. Effects on the seals' behaviour were quantified at three threshold SPLs: one which did not cause behavioural changes (128 dB re 1 µPa @ 1 m (RMS)), one which caused one of the seals to haul out occasionally (133 dB re 1 µPa @ 1 m (RMS)), and one which caused one of the seals to haul out more than 10% of the time (138 dB re 1 µPa @ 1 m (RMS)). The lack of response by the seals to the Lofitech AMD sound was unexpected, though the SL of the actual Lofitech is much higher than the maximum SL that was used in the present study. Small changes in behaviour were observed during the pre-tests, but these were not statistically significant in the main study. Thus at similar received levels under the conditions tested, the authors reported that the Ace Aquatec seems more effective than the Lofitech in deterring harbour seals. | Kastelein et al., 2015b | |
| Grey Seal | Field Study (Salmon & Whitefish Fishery) | ADDs were deployed during three consecutive fishing seasons. However, the ADDs were modified slightly; device usually operates at a duty cycle of between 9 to 10%; the authors partly used a modified version with a duty cycle of 4.5% by reducing the pulse length to 250 ms. Catches were significantly higher in traps with ADDs (25.5 kg d−1) than in controls (12.0 kg d−1), and catch damage was less (3.5 vs. 6.7 kg d−1). These results persisted over and between fishing seasons, but late in the season damage to the catches was common also in traps with ADDs. | Fjälling et al., 2006 | |
| Grey & Harbour Seal | Captive Study & Field Study | Playback experiments with both grey and harbour seals were carried out in captivity and in the wild, with different sound sources including four types of ADD (but with lower SLs). In captivity, food motivation was introduced and mean RLs (RMS) for all sounds in the pool ranged from 142-147 dB re 1 µPa. Playback experiments in the wild used broadband SLs of 172 dB re 1 µPa (RMS). A single emission of sounds in the field experiment (10 s burst) would result in a SEL of 182 dB re. 1 µPa2s and a single emission (6 s) in the captive trials would amount to a SEL of 156 dB re 1 µPa2s. In captivity with food motivation, seals did not respond differently to the different sound types and habituation in both grey and harbour seals occurred at RL of 146 dB re 1 μPa (RMS). In the wild, for signals resembling that of a Lofitech ADD (but with a lower SL), the deterrence range was 60 m with an avoidance threshold of 138 dB re 1 µPa (RMS). | Götz & Janik, 2010 | |
| Lofitech 'Simulated signals' | Harbour Seal | Field Study | In Denmark, wild harbour seals were exposed to simulated ADD sounds that resemble a Lofitech ADD but with a reduced SL (165 dB re 1 µPa (p-p); compared with 189 dB re 1 µPa (RMS) of a real Lofitech) to allow closer exposure to visual tracking. There was an increase in seal observations within 100 m of device when active. Seals did not evade the sound source and were observed more often and closer to the ADD during sound exposures than in control periods. Some individuals approached the device within approximately 10 m at RLs exceeding 142 dB re 1 µPa. No deterrence thresholds could be generated due to the lack of an avoidance response. As significantly more seals were observed just after sound was played compared to just before, the reduced sound source appeared to attract the seals instead of deterring them. | Mikkelsen et al., 2017 |
| Terecos 'Unknown' | Grey Seal & Harbour Seal | Captive Study & Field Study | Playback experiments with both grey and harbour seals were carried out in captivity and in the wild, with different sound sources including four models of ADD (but with lower SLs). In captivity, food motivation was introduced and mean RLs (RMS) for all sounds in the pool ranged from 142-147 dB re 1 µPa. Playback experiments in the wild used broadband SLs of 172 dB re 1 µPa (RMS). A single emission of sounds in the field experiment (10 s burst) resulted in a SEL of 182 dB re. 1 µPa2s and a single emission (6 s) in the captive trials corresponded to a SEL of 156 dB re 1Pa2s. In captivity with food motivation, seals did not respond differently to the different sound types and habituation in both grey and harbour seals occurred at RL of 146 dB re 1 μPa (RMS). In the wild, for signals resembling that of a Terecos ADD no deterrence distance was found. | Götz & Janik, 2010 |
| Device | Species | Use | Study Summary | Reference(s) |
|---|---|---|---|---|
| Bespoke ADD signals (i.e. not from a specific manufacturer) | Harbour Seal | Field Study | In an experimental field study with harbour seals, high frequency test signal was designed using single frequency tonal bursts between 8 – 18 kHz, similar to signals produced by the Airmar, Lofitech and Ace Aquatec devices (the random frequency sequencing and the pulse width and duty cycle of the Ace Aquatec were also adopted). A low frequency test signal was also made up of pulsed continuous wave sinusoidal tonal bursts at one of 11 randomly switching fundamental frequencies between 1 – 2 kHz and frequency intervals at 100 Hz. This signal was designed to produce outputs comparable to those from the Ace Aquatec US3 low frequency variant ADD design. The source levels used were lower (approximately 170 dB re 1 μPa @ 1 m (RMS)) than manufactured devices. Although not the focus of the study, harbour seals were not noticeably deterred from the vicinity of the fish farm by experimental ADD signal emissions, with no obvious difference between high frequency or low frequency signals in terms of surface observations. | Benjamins et al., 2018 |
| Industry response | Reference(s) |
|---|---|
| A survey amongst Scottish aquaculture sites reported that out of 28 fish escape incidents that had been thought to be caused by predators, 9 occurred at sites using ADD and 12 at sites not using ADDs, while the availability of ADDs at the remaining 7 sites was unknown. However it is unknown if all the sites that had been using ADDs at the time had the devices switched on during escape incidents. | Thistle Environmental Partnership (TEP), 2010 |
| A survey of 49 stakeholders with responsibility for over 136 different sites reported that ADDs were in use at 40 sites and not in use at 41 sites. At 16 of the 40 sites ADDs are used continuously; at 12 sites ADDs are only switched on when the fish become large enough to be considered at risk; at 4 sites ADDs are switched on when seals are seen close to the cages; while at 21 sites ADDs are only used when seal damage begins to be noted. The majority of stakeholders thought that the use of ADDs reduced seal attacks without eliminating them, and at 15/20 sites they were judged overall to have some preventative effect, and not at 5. Habituation to ADD signals was considered a problem for 41 sites, but not at a further 10. | Northridge et al., 2010 |
| A questionnaire study of aquaculture sites in Scotland where a variety of ADDs were used reported that only 23% of fish farmers reported ADDs to be very effective, 50% reported moderate, 15% poor and 7% little efficiency. | Quick et al., 2004 |
| Device | Sound pressure level output (as stated by manufacturer) | Frequency: (kHz) | Duty Cycle | Signal type and duty cycle |
|---|---|---|---|---|
| Ace Aquatec - RT1* | 195 dB re 1 µPa @ 1 m (RMS). | Previously 1 – 5 kHz, but recently restricted to 1 – 2 kHz in applications near harbour porpoise | Intermittent | A random selection of pulses in 2 – 5 s cycles. |
| Ace Aquatec - US3 (previously 'Silent Scrammer'/ US2) | 195 dB re 1 µPa @ 1 m (RMS). | 10 – 20 kHz | Intermittent | A random selection of pulses in 2 – 5 s cycles. |
| Airmar - dB plus II | 198 dB re 1 µPa @ 1 m (RMS). | Broadband, with detectable energy levels between 1.5 - 50 kHz | Continuous | Sequence of pulsed sinusoidal total bursts. Each tonal burst is ~1.4 ms in duration with 40 ms interval. A 2.25 s long sequence is then formed from 57-58 tone bursts. The sequence is then repeated with ~50% duty cycle allowing ~2 s quiet period. |
| Mohn Aqua MAG Seal Deterrent | 198 dB re 1µPa at 1m (RMS). | Broadband, with detectable energy levels between 1.5kHz to 50kHz | Continuous | Sequence of pulsed sinusoidal total bursts. Each tonal burst is ~1.4ms in duration with 40ms interval. A 2.25s long sequence is then formed from 57-58 tone bursts. The sequence is then repeated with ~50% duty cycle allowing ~2s quiet period. |
| GaelForce SeaGuard | 198 dB re 1µPa at 1m (RMS). | Broadband, with detectable energy levels between 1.5kHz to 50kHz | Continuous | Sequence of pulsed sinusoidal total bursts. Each tonal burst is ~1.4ms in duration with 40ms interval. A 2.25s long sequence is then formed from 57-58 tone bursts. The sequence is then repeated with ~50% duty cycle allowing ~2s quiet period. |
| OTAQ | Protect mode: sound pressure level output = 189 dB re 1 µPa @ 1 m (RMS). | 9-11 kHz | Intermittent | Patrol mode: 2 s transmissions with 20 s gap between pulses Protect mode: 3 second transmissions with random pulse gaps of between 3 and 10 s |
| Patrol mode: sound pressure level output = 165 dB re 1 µPa @ 1 m (RMS). | ||||
| Terecos - DSMS-4 | Prog 1: Measured 177 dB re 1 µPa @ 1 m (RMS). | 1.8 kHz - 3.8 kHz (Prog 1) | Continuous | Repetitive five segment 16 ms continuous tonal blocks forming an up and down frequency sweep. Fundamental frequencies ranging from 1.8 - 3.8 kHz with uniformly distributed harmonic components. |
| Prog 2: Measured 178--9 dB re 1 µPa @ 1 m (RMS). | 4.7 kHz & 6.8 kHz (Prog 2) | Continuous | Multi-component continuous tones with observed peak level frequencies of 4.7 kHz and 6.8 kHz. Both contain complex multiple frequency components with a broad energy distribution away from the peak level tonal component. | |
| Prog 3: Measured 178 dB re 1 µPa @ 1 m (RMS). | 2.4 – 6.0 kHz | Continuous | Sequence of 8 segments (8 ms) forming continuous tonal blocks forming an up and down frequency sweep. Fundamental frequencies ranging from 2.4 – 6.0 kHz with uniformly distributed harmonic components |
* For these four devices (Ace-Aquatec RT1, OTAQ, MohnAqua and GaelForce), we are not aware of any published evidence relating their efficacy or impact on marine mammals. They are included in this table as they are known to be used at Scottish aquaculture sites. Note: the MohnAqua and GaelForce have the same acoustic properties as the Airmar device.
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