A Duck’s Beak with Porpoise: Sightings of Cetaceans During and After a 3D Seismic Survey in the German North Sea

Ian B. Todd¹ and *Victoria L. G. Todd¹

¹Ocean Science Consulting, Spott Road, Dunbar, East Lothian, EH42 1RR, Scotland, UK.

*Correspondent E-mail ✉: vt@osc.co.uk

Accepted August 03, 2025

Large-scale, inter-governmentally funded offshore marine mammal surveys are costly, leading to infrequent and often inadequate spatial data coverage, especially in Special Areas of Conservation (SACs). Conversely, offshore Oil & Gas Exploration and Production operators and renewables developers must perform extensive Environmental Impact Assessments to meet permit conditions, providing a potential source of valuable scientific data. In 2007, spring and summer line-transect surveys collected marine mammal observer data during (Survey 1 (S1)) and after (Survey 2 (S2)) the final seismic 3D survey in German waters (Entenschnabel ‘Ducks’ beak’ Dogger Bank SAC). S1 reported 31 marine mammal sightings (110 individuals, four species); S2 resulted in ten sightings (22 individuals, three species). S1/S2 porpoise (Phocoena phocoena) sightings were similar, but S1 group size was smaller; spring density (ca. 6 porpoises/km²) was lower than summer (ca. 16 porpoises/km²). Conversely, minke whale (Balaenoptera acutorostrata) sightings were higher in spring (ca. 20 minke/km²) compared to summer (ca. one minke/km²). No evidence supported seismic survey effects on any species; differences in abundance were likely related to seasonal/prey movements. Results provide valuable sightings in this remote, yet highly developed, section of the North Sea, informing future EIAs for O&G E&P operators and renewable-infrastructure developers in the Dogger Bank SAC.

Key words: Abundance, Density, Distance Sampling, Dogger Bank, Marine Mammals, North Sea, Seismic Surve

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