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 (Globicephalaspp.) 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.
Highlights
Marine ecological monitoring programmes have become an important tool for environmental management worldwide (Borja et al, 2008; Borja & Elliott, 2013)
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 marine mammal incidental sightings corresponding to about 288 individuals were reported during the three years of the marine mammal sighting reporting programme (MMSR; 1 May 2013 to 1 May 2016; Table 2)
Summary
Marine ecological monitoring programmes have become an important tool for environmental management worldwide (Borja et al, 2008; Borja & Elliott, 2013). The programmes provide managers and decision-makers with an essential source of relevant, reliable and timely science-based information that can be used to support the decision-making process (Elliott, 2011). The North Sea is a region with a wide range of industrial activities (OSPAR, 2010; Andersen et al, 2013) and it is home for several protected marine mammal species (Kinze, 2001; Reid et al, 2003; Hammond et al, 2013). Alternative methods based on incidental sightings by sea-users (e.g. recreational sailors, fishermen, ferry goers) may be a cost-effective means to provide complementary valuable information to large regional surveys (Evans et al, 2003; Kinze et al, 2003; Loos et al, 2009; Palacios et al, 2012).
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