The Ecology and Feeding Habits of Fish Assemblages Closely Associated with Offshore Oil and Gas Platforms in the North Sea

Despite the large number of offshore oil and gas platforms currently installed in the North Sea, little is known about the role of such large fixed offshore structures in the ecology of fish populations in this region. This presentation reports the results of the first detailed study on feeding habits of fish assemblages closely associated with offshore oil/gas platforms in the North Sea. Multi-seasonal fish sampling was conducted at one of the oil platforms located in the Central North Sea (September 2010 - January 2014), and the results revealed that commercially important gadoids such as saithe (Pollachius virens), haddock (Melanogrammus aeglefinus) and cod (Gadus morhua) were the most abundant species. Saithe fed predominantly on euphausiids and haddock consumed large proportion of ophiuroids, whereas cod were mainly piscivorous. Their prey compositions were significantly different between species, indicating individual offshore installations could provide unique feeding grounds for a variety of fish species and thereby allow for interspecific prey resource partitioning among those species closely associated with the structure. To further investigate possible links between the feeding habits of the most dominant fish species, saithe, and the physical presence of offshore platforms across the North Sea, a separate set of stomach data were collected during the 2012 Q3 International Bottom Trawl Survey. The multivariate analysis showed the observed spatio-temporal variability in saithe diet was significantly explained by proximity to the nearest offshore platforms and changes in water temperatures, which appear to reflect patterns of euphausiid availability over space and time. The physical presence of the offshore structures may affect the distribution/availability of euphausiids and thereby influence the feeding behaviour of saithe and possibly other marine populations that are interconnected to the dynamics of such trophic interactions in the North Sea.