Marine communities of the Bayu-Undan pipeline: comparisons with natural seabed communities to provide context for decommissioning

A major focus of the research was on fish, including the top 10 commercially important fishery species for this region, given their role as biodiversity indicators and the interest of this faunal group to a broad range of stakeholders. Field research was conducted in August-September 2019 aboard the AIMS vessel RV Solander. Five locations were surveyed along the pipeline route each location included the pipeline and surrounding natural seabed ecosystems out to a maximum distance of 6 km from the pipeline.

A suite of methods was employed to characterise seabed morphology and associated biota. A multibeam echosounder acquired bathymetry raster data which revealed seabed depth and morphology. Subsequent derivative datasets produced environmental predictors of benthos describing seafloor structure and complexity. Towed video was used to collect high resolution imagery of benthic communities along 1.5km transects, randomly stratified across different habitat types, where visibility permitted. As it was not possible to perform towed video transects along the pipeline in high currents and low visibility, information on benthic communities colonising the pipeline was obtained through the analysis of existing remotely operated vehicle (ROV) imagery of the pipeline that was collected in 2017 by ConocoPhillips. Fish species richness and abundance, in addition to the size of commercially important fish species, were obtained using baited remote underwater stereo-video systems (stereo-BRUVs) with sampling along the pipeline and randomly stratified across natural seabed ecosystems at each location. The size of commercially important fish species was converted to biomass and beach value ($). AIMS historical data on benthic habitats and fish diversity were included to provide context and regional assessments of marine communities