Assessing fish assemblages on oil jackets off the Angolan coast: Implications for decommissioning decisions

West Africa plays a significant role in global oil production. Much of the offshore infrastructure in this region is due for decommissioning. An understanding of the marine communities associated with the infrastructure is essential to predict the outcome of different decommissioning alternatives, such as leave-in-place or full removal. Using ROV inspection footage, we sampled nine jackets off Angola (Cabinda Province) to quantify the abundance and species composition of fish. Sixty-five species of fish were observed among jackets, including several taxa that are commercially important to the region, such as sardine (Sardinella spp.) and mackerel species (Trachurus spp.). We also observed taxa that are commonly targeted in small-scale (artisanal) fisheries in Angola, such as groupers (Epinephelidae) and snappers (Lutjanidae). Distinct fish assemblages were observed at each jacket, and attributed to differences in jacket location, depth, and infrastructure design. Time of day also affected the assemblage detected across jackets, although similar dominant families were present across day and night at a specific depth zone when pooled. Unlike patterns observed in other regions, there was not a clear depth zonation pattern at individual jackets, and only a weak depth zonation pattern was evident when all jackets were combined. Six species had not previously been recorded off Angola, suggesting that the jackets may either facilitate range extensions or highlight a paucity of fish studies in the region. Our results have important implications for evaluating decommissioning options, including addressing questions on jacket removal or reefing and implications for species of importance to fisheries.