Abstract
A decade of visual and acoustic detections of marine megafauna around offshore Oil & Gas (O&G) installations in the North and Irish Seas are presented. Marine megafauna activity was monitored visually and acoustically by Joint Nature Conservation Committee (JNCC) qualified and experienced Marine Mammal Observers (MMO) and Passive Acoustic Monitoring (PAM) Operators respectively, with real-time towed PAM in combination with industry standard software, PAMGuard. Monitoring was performed during routine O&G industrial operations for underwater noise mitigation purposes, and to ensure adherence to regulatory guidelines. Incidental sightings by off-effort MMOs and installation crew were also reported. Visual and acoustic monitoring spanned 55 non-consecutive days between 2004 and 2014. A total of 47 marine mammal sightings were recorded by MMOs on dedicated watch, and 10 incidental sightings of marine megafauna were reported over 10 years. Species included: harbour porpoise (Phocoena phocoena), Atlantic white-sided dolphin (Lagenorhynchus acutus), white beaked dolphin (Lagenorhynchus albirostris), common dolphin (Delphinus delphis), minke whale (Balaenoptera acutorostrata), common seal (Phoca vitulina), grey seal (Halichoerus grypus) and, basking shark (Cetorhinus maximus). Passive Acoustic Monitoring was conducted on two occasions in 2014; 160 PAM hours over 12 days recorded a total of 308 individual clicks identified as harbour porpoises. These appear to be the first such acoustic detections obtained from a North Sea drilling rig whilst using a typically configured hydrophone array designed for towing in combination with real-time PAMGuard software. This study provides evidence that marine megafauna are present around mobile and stationary offshore O&G installations during routine operational activities. On this basis, Environmental Impact Assessments (EIAs) for decommissioning O&G platforms should be carried-out on a case-by-case basis, and must include provisions for hitherto overlooked marine megafauna.
Highlights
Despite a recent fall in oil prices, the global demand for Oil and Gas (O&G) exploration and production continues to increase
This paper presents visual and acoustic evidence of marine megafauna present around mobile and stationary offshore installations in the North and Irish Seas
38% (12 days) of visual monitoring during tows was conducted in conditions considered conducive for visual monitoring of marine mammals
Summary
Despite a recent fall in oil prices, the global demand for Oil and Gas (O&G) exploration and production continues to increase. During 2014 in the UK alone, £14.8 billion was spent exploring for (and developing) O&G reserves [1], with a current 776 platforms operating in the North Sea today. In the UK North Sea sector, estimations of cumulative taxpayer expenditure for decommissioning range from £30–75+ billion over the 30 years, depending on sources consulted (e.g. Oil & Gas UK, Oil & Gas Authority, Decom North Sea, etc.). Decommissioning is at the forefront of industry and Governmental agendas, but complete removal is a highly complex activity that has currently unknown and quantified Health, Safety, Environmental (HSE), financial, political, and social implications. Leaving O&G structures in situ as artificial reefs is a potential alternative, and is known as a Rigs-to-Reefs (RTR) scheme. RTR schemes have been implemented successfully in Brunei [3] and the United States’ Gulf of México [4]. RTR was legislated as an option in the State of California (and is gaining scientific credence from a variety of different research approaches), but opposition has prevented its implementation [5,6,7,8]
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