Marine mammal sightings around oil and gas installations in the central North Sea

Abstract

Relatively little is known about the distribution and diversity of marine mammals around offshore anthropogenic structures. We present results obtained from incidental sightings of marine mammals around oil and gas installations located 200 km off the Danish coast. A total of 131 sightings corresponding to about 288 animals were reported between May 2013 and May 2016. A total of seven marine mammal species were identified, five cetaceans: harbour porpoise (Phocoena phocoena), minke whale (Balaenoptera acutorostrata), white-beaked dolphin (Lagenorhynchus albirostris), killer whale (Orcinus orca), pilot whales (Globicephala spp.) and two species of pinnipeds: harbour (Phoca vitulina) and grey seals (Halichoerus grypus). The most sighted species were harbour porpoise (41%) and minke whale (31%). Relative counts and biodiversity of marine mammals observed around installations corresponded well with the expected distribution in the central North Sea. Several taxon-specific correlations were identified between number of sightings and environmental parameters (depth and latitude) or installation characteristics (installation aerial footprint). Furthermore, 85% of sightings were made during spring and summer and it is unclear whether the pattern observed reflected a natural seasonal occurrence of marine mammals in the area or an effect of reduced effort during autumn and winter. Despite the potential caveats, results obtained during this programme provide an insight into the relationship between marine mammals and oil and gas offshore installations in the North Sea.

Underwater Visual Records of Marine Megafauna Around Offshore Anthropogenic Structures

“…Previous acoustic and surface-based visual studies that have detected marine mammals around O&G structures (e.g., Cremer et al, 2009;Todd et al, 2009Todd et al, , 2016Thompson et al, 2010;Delefosse et al, 2018), have now been corroborated by the commercial subsea imagery in this study. Presence of other megafauna species such as sharks (Haugen and Papastamatiou, 2019), rays, and turtles (McLean et al, 2017(McLean et al, , 2019b confirm that marine mammals are not unique in their exploitation of resources on/around anthropogenic structures.…”

“…Another North and Irish Sea acoustic and visual study on various offshore O&G installations, reported multiple marine mammal species, including harbor porpoise, Atlantic white-sided (Lagenorhynchus acutus), white-beaked (Lagenorhynchus albirostris), and common (Delphinus delphis) dolphin, minke whale (Balaenoptera acutorostrata), and both common (Phoca vitulina) and gray (Halichoerus grypus) seal (Todd et al, 2016). Similarly, Delefosse et al (2018) analyzed visual sightings from 25 O&G installations in the Dutch sector of the North Sea, recording 131 sightings of 288 individual marine mammals over a 3-year period. Harbor porpoise was the most commonly sighted species (41% of sightings), followed by minke whale (31%).…”

Using cost-effective surveys from platforms of opportunity to assess cetacean occurrence patterns for marine park management in the heart of the Coral Triangle

“…Still, even considering these caveats, the data collected during the non-systematic surveys enable the construction of a positively identified species list and a first indication of the cetacean population status and density. The applied method provides a low-cost approach to obtain valuable long-term information for areas with limited or no specific monitoring effort over a wide geographic area (Delefosse et al, 2018). Although interpretation of nonsystematically collected data is difficult without measure of effort (Evans and Hammond, 2004), with stringent data filtering and quality control, valuable information can be obtained (Pikesley et al, 2012).…”

Midnight at the oasis: does restoration change the rigs-to-reefs debate in the North Sea?

“…Advocates argue that the rigs mimic the stone reefs that were once more prevalent in the North Sea and provide the hard substrate needed for blue mussels and corals to colonize (A. M. Jørgensen, 2018;Pearce, 2018;Sonne, 2018). Proponents refer to the research on their mimicry of natural structures (Henry, Harries, Kingston, & Roberts, 2017), enhanced productivity (Claisse et al, 2014;Fowler et al, 2018), marine mammal attraction (Delefosse, Rahbek, Roesen, & Clausen, 2018), and growing scientific consensus on revising artificial reef guidelines in OSPAR (Fowler et al, 2018).…”