Increased fish abundance, biodiversity, and body size near a North Sea oil and gas platform

In the North Sea, offshore oil and gas (O&G) platforms must be totally removed through decommissioning at the end of their productive life. However, the role of O&G platforms in marine ecosystems, especially for fish assemblages, is not well enough defined yet. Here, we document the association between an O&G platform in the North Sea and the fish assemblages along a distance gradient of 1 – 600 m from the platform. Scientific angling provided data on fish biodiversity, abundance, and body size. In addition, acoustic data on fish density and target strength were collected to explore spatial and diel fish distributions. The angling data comprised 1217 fish from 11 species, with the highest fish abundance, and all species occurring, within 20 m from the platform. Platform proximity was positively associated with fish biodiversity, and total fish abundance, as well as the specific abundances of Atlantic cod Gadus morhua , dab Limanda limanda , whiting Merlangius merlangus , and mackerel Scomber scombrus . Body sizes of Atlantic cod, whiting, and mackerel were also positively associated with the platform. Absent non-native or invasive species provided no support for stepping stone scenarios. This study highlights the attraction of a variety of fish species towards O&G platforms in the North Sea. Potential local loss of marine biodiversity following full platform removal should be considered in future discussions on platform decommissioning policies. • Fish biodiversity and abundance were greater within 20 m of the platform. • Individual fish body size was positively associated with platform proximity. • No non-native species were observed in the study area. • Hydroacoustics data showed potential diel fish distribution patterns. • Platform removal may impact local fish communities.