The Carbon Trust managed the new research to build confidence in the use of Acoustic Deterrent Devices Devices (ADDs) - a series of amplified electronic pulses projected into the water - to safeguard marine mammals during deep water offshore wind construction. It was as an Offshore Renewables Joint industry Programme (ORJIP), with funding from innogy, Ørsted, and Statoil.
The research shows for the first time that ADDs act as warning signals that deter minke whales from wind farm construction sites.
Previous studies have demonstrated that ADDs effectively deter seals and harbour porpoise, however, until now there has been little research into the use of ADDs as a deterrent for minke whales. As minke whales are an important species in UK waters, the ORJIP study was set up to address this knowledge gap. The objective was to increase confidence in ADDs and specifically improve the techniques for safely deterring marine mammals during offshore wind construction. During the field research whales were observed to display a clear and sustained movement away from the ADD deployment site, adopting faster swim speeds with more directed movement.
During the construction of wind farms, where percussive pile driving is required for foundation installation, increased underwater noise levels are generated. The detection of marine mammals is currently carried out by marine mammal observers posted offshore, or passive acoustic monitoring (PAM). If a marine mammal is detected close to an offshore wind construction site, piling activity will not commence until it is deemed that there are no longer marine mammals within the predefined zone.
The ability to use active acoustic systems to create a temporary safety exclusion zone around the turbine is a useful addition to the suite of mitigation options for wind farms developers. In particular, it increases confidence that marine mammals are adequately protected when operating in harsh conditions or poor visibility, and also avoids the need to unnecessarily delay construction operations.
Olivia Burke, manager of the ORJIP ADD project at the Carbon Trust said: "The findings will help increase industry and regulator confidence in the use of ADDs to actively manage the protection of marine mammals during the piling phase of construction."
Tracking results demonstrated that focal minke whales responded to ADDs at distances which could prevent injurious effects of subsea noise. The study revealed that the selection of appropriate ADDs for mammals with different hearing frequencies and appropriate deployment periods for the underwater environment were important considerations to ensure successful ADD deployment.
This research was undertaken by RPS Energy and MCR on behalf of the ORJIP programme . The findings could also reduce the number of personnel deployed to monitor marine mammal presence offshore to minimise health and safety risks as the industry continues to grow.
During the research a total of 246 minke whales were sighted, of which 46 focal whales were tracked. Focal follows including successful ADD deployment were carried out on 15 occasions. In all 15 deployments, the focal animal moved away from the ADD deployment site following activation of the unit.
The study site was located in Faxaflói Bay, southwest Iceland, selected as it is a summer feeding ground for minke whales therefore ensuring a high whale population density. Researchers worked from the specialist cetacean research vessel Song of the Whale and a secondary smaller vessel to ensure minimal disturbance. The Lofitech ADD device was chosen for the research as it had the greatest body of scientific evidence demonstrating efficacy at deterring other marine mammals. Video range tracking (VRT) was employed to measure minke whale response to ADDs during the Control Exposure Experiments.
Carbon Trust ORJIP offshore wind