Fish associated with subsea pipelines and their rock berms
Sean van Elden | May 2022
New publication and poster presentation
The ecological role of subsea pipelines is an important factor in the consideration of decommissioning options. Several studies have assessed the marine communities associated with subsea pipelines on Australia’s North West Shelf (NWS), considering the influence of factors such as water depth, substrate type, pipeline diameter and pipeline position on fish assemblages. Less is known about the artificial rock berms used to stabilise pipelines. The Wandoo field on the NWS consists of an unmanned monopod and a concrete gravity structure, with three pipelines connecting these structures: a 4″ Gas Flowline, an 8″ Test Flowline and a 12″ Production Flowline.
These pipelines are buried, exposed or span the seabed and are supported by rock berms at regular intervals. We present a novel frame-based, timed-count method to assess the fish communities associated with subsea pipelines utilising archival remotely operated vehicle footage that lacks geospatial data. We apply this approach to a pipeline in the Wandoo field to document variation in the fish assemblage with pipeline position (buried, exposed, span or covered by rock berm). Overall, diversity and abundance were higher on pipeline covered by rock berms than on the other pipeline positions.
We hypothesise that rock berms are effectively artificial reefs, providing complex habitat structure and facilitating growth of macrobenthos communities that are associated with higher fish diversity. We demonstrate that rock berms can increase the ecological value of subsea pipelines and should therefore be a priority area for future ecological surveys.
Citation: van Elden Sean, Tothill Thomas, Meeuwig Jessica J. (2022) Fish associated with subsea pipelines and their rock berms. The APPEA Journal 62, S362-S367.
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Rock berm
The image shows a rock berm in the Wandoo field colonised by sponges, with a school of golden trevally (Gnathanodon speciosus).
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APPEA Conference 2022
Poster presentation at the Australian Petroleum Production & Exploration Association conference in Brisbane.
Funding and Acknowledgements
Thanks to Vermilion for their support of this project and provision of ROV footage.