Acoustic Studies
The Marine Directorate has led several passive acoustic monitoring (PAM) projects since 2013. Through the use of static passive acoustic recorders (click detectors and broadband sound recorders), MD-SEDD has collected data on cetacean vocalisations and underwater noise levels. This allows us to address critical knowledge gaps on cetacean distribution required to inform offshore wind policy, planning and consenting of licensed marine activities, and to inform Marine Protected Areas management, alongside characterisation of the acoustic environment, to monitor the impact of human activity on the underwater soundscape and the statutory reporting of underwater noise levels.
Underwater noise and its potential impacts on marine mammals and other marine species is a key consenting issue for offshore wind farms and a range of other licensable marine activities. For many areas of Scottish waters, particularly those located further offshore, there is limited information available on the presence or distribution of cetaceans. This presents a challenge for assessments of potential impacts of proposed activities such as offshore wind farms, as well as the identification and delivery of appropriate cetacean conservation measures.
East Coast Marine Mammal Acoustic Study (ECOMMAS)
The Marine Directorate (formerly Marine Scotland) established the East Coast Marine Mammal Acoustic Study (ECOMMAS) project in 2013, with the aim of monitoring the effects of offshore wind farm construction on harbour porpoise and bottlenose dolphin.
The waters around the east coast of Scotland are home to many species of marine mammals, including, harbour porpoise (Phocoena phocoena) and bottlenose dolphin (Tursiops truncatus). The harbour porpoise is the most abundant cetacean species in the North Sea, with a large population size and wide distribution (Gilles et al., 2023). The much smaller coastal population of bottlenose dolphins is protected by a designated Special Area of Conservation (SAC) (JNCC website, 2024) in the inner Moray Firth.
Dolphins and porpoises (odontocetes; toothed whales) use echolocation clicks to navigate, catch prey and communicate. Echolocation can be disrupted by underwater noise, including sounds from boat traffic, geophysical surveys and infrastructure construction. Information on habitat use by bottlenose dolphins and harbour porpoises is important to understand how these species use the coastal waters of Scotland and the potential for offshore marine industries to affect their behaviour. Both species are protected under UK and international law.
The ECOMMAS project used click detectors, known as PODs (Chelonia Ltd.; www.chelonia.co.uk), and deployed ten arrays of three detectors each (giving 30 locations in total) off the east coast of Scotland, to detect echolocation clicks produced by both porpoises and dolphin species. At one location within each of the ten arrays, a broadband acoustic recorder was also deployed, to record ambient noise levels and other animal vocalisations.
At the start of ECOMMAS in 2013, these devices were deployed at sea throughout the summer every year, having a battery life of around 4 months. Due to advancements in technology and capability, the proportion of the year for which data could be collected increased over time. From 2015, two deployments were undertaken per year, meaning that there were data covering the period from April to November, and from 2016 two sites (Arbroath and Helmsdale) had a third deployment implemented to cover the winter season.
Broadband recorders were used to collect acoustic data spanning a frequency range of 50 Hz to 48 kHz. This provided data within the frequency bands of interest for a suite of marine mammal vocalisations, such as dolphin whistles. The broadband data have also been used for underwater noise monitoring as part of reporting requirements under OSPAR and UK Marine Strategy (updated UK Marine Strategy Part Two), namely the third octave bands at 63 Hz and 125 Hz. A subset of the ECOMMAS broadband data were published as part of the first assessment of baseline underwater noise levels in UK waters (Merchant et al. 2016).
Automated click detectors C-PODs and their successors, F-PODs (Chelonia Ltd.; www.chelonia.co.uk), were deployed to monitor species such as harbour porpoise which produce high-frequency signals. The automated click detectors process data in real-time and only record specific features of these signals that meet certain detection criteria, based on frequency, time and amplitude characteristics. The recorded click detection data and associated acoustic metrics can be summarised across variable time scales (e.g. by minute, hour or day). The presence/absence data of porpoises and dolphins can be extracted as detection-positive days (DPD) and detection-positive hours (DPH).
Between 2013 and 2023 and across the 30 locations, a total of 49,836 days of data were collected. The complete list of research publications is listed within the publications section below). For additional information on ECOMMAS visit the link to the ECOMMAS topic sheet provided within the Additional Information section below.
The Scottish Passive Acoustic Network (SPAN)
The SPAN project is funded through ScotMER (Science and research - Marine renewable energy - gov.scot) and it builds upon the ECOMMAS project on the east coast of Scotland. SPAN also maintains PAM deployments on the west of Scotland from projects completed in late 2022; the COMPASS project (Collaborative Oceanography and Monitoring for Protected Areas and Species; https://compass-oceanscience.eu), the MarPAMM project (Marine Protected Area Management and Monitoring; https//www.mpa-management.eu); and the Static acoustic monitoring of Scottish Atlantic seas (SAMOSAS) project, an EMFF funded project coordinated by Marine Directorate (Marine Scotland) and commissioned to the Scottish Association for Marine Science (SAMS). In addition, SPAN was conceived to expand monitoring into data deficient areas such as the Northern Isles (Orkney and Shetland) and into more offshore waters (Figure 2).
ECOMMAS and SPAN Data
The deployment details and processed POD data for ECOMMAS from 2013-2023 and for SPAN from 2023-2025 are available to download as excel spreadsheets with the data agreement conditions specified (see Data Sources section within the Links and Resources below). Included in both spreadsheets are the PAM mooring locations, dates and times for all sites where data are available, and detection positive hours (DPH) of porpoise and dolphin species per day. The processed ECOMMAS POD data are also available on the Marine Scotland Maps NMPi (see below Marine Portal Data Link below under Data Sources).
The available broadband data details for both ECOMMAS and SPAN from 2013 onwards can be found below (see Data Sources section within the Links and Resources below).
Broadband data and raw POD data files (CP1 files) are available by request and under the further data agreement conditions specified by contacting acoustics@gov.scot.
