Question reference: S5W-36094
- Asked by: Mark Ruskell, MSP for Mid Scotland and Fife, Scottish Green Party
- Date lodged: 11 March 2021
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Current status: Answered by Ben Macpherson on 23 March 2021
Question
To ask the Scottish Government what the sound pressure level in decibels was at which Kok et al (2017) recorded avoidance by harbour porpoises; what the sound pressure level was at which Brandt et al (2012) recorded a 96% reduction in porpoise clicks at a station 7kms away from a single Lofitec acoustic deterrent device, and what sound pressure level in decibels Marine Scotland has determined as the threshold for disturbance for small cetaceans.
Answer
The papers cited in this question are both available in the public domain. The type of Acoustic Deterrent Device used in the Brandt et al. (2012) study (Lofitech) is only used in Scottish waters as a mitigation to move marine mammals out of areas where they may be injured by construction or blasting noise. It is not in use at Scottish fish farms (Scottish Government 2021).
The threshold applied by the Government of 120 dB re 1 µPa (rms) for the onset of potential disturbance from non-impulsive sounds is based upon guidance from the US National Oceanic and Atmospheric Administration ( ESA Section 7 Consultation Tools for Marine Mammals on the West Coast | NOAA Fisheries ).