Fish associated with a subsea pipeline and adjacent seafloor of the North West Shelf of Western Australia

Abstract

Information on the potential ecological value of offshore oil and gas infrastructure is required as it reaches the end of its operational life and decisions must be made regarding the best practice option for decommissioning. This study uses baited remote underwater stereo-video systems to assess fish assemblages along an offshore subsea pipeline and in adjacent natural seabed habitats at ∼140 m depth on the North West Shelf of Western Australia. A total of 955 fish from 40 species and 25 families were recorded. Species richness was, on average 25% higher on the pipeline (6.48 ± 0.37 SE) than off (4.81 ± 0.28 SE) while relative abundance of fish was nearly double on the pipeline (20.38 ± 2.81 SE) than in adjacent natural habitats (10.97 ± 1.02 SE). The pipeline was characterised by large, commercially important species known to associate with complex epibenthic habitat and, as such, possessed a biomass of commercial fish ca 7.5 × higher and catch value ca. 8.6 × ($65.11 ± $11.14 SE) than in adjacent natural habitats ($7.57 ± $2.41 SE). This study has added to the knowledge of fish assemblage associations with subsea infrastructure and provides a greater understanding of the ecological and fisheries implications of decommissioning, helping to better inform decision-making on the fate of infrastructure.