Project Description
Offshore oil and gas (O&G) infrastructure such as pipelines, wells and platforms have proliferated along continental margins worldwide. These structures are colonised by sessile and motile invertebrates to form artificial reefs, which in turn attract fish and larger fauna (Thomson et al. 2018, McLean et al. 2019). The role of these structures as artificial reefs has attracted greater attention worldwide as they age and as the industry considers decommissioning options (Macreadie et al. 2011, Bull et al. 2019). In regions such as the Gulf of Mexico, obsolete oil platforms have been left in place as part of the ‘Rigs to Reef’ program, where they form additional habitat that has ultimately increased the abundance of recreationally and commercially important fish species (Downey et al. 2018). In Australia, decommissioning science is particularly topical with the recent formation of the National Decommission Research Initiative (NDRI) established to ultimately provide an evidence base to inform decommissioning decisions.
Marine megafauna such as sharks, manta rays, sea turtles, seals, dolphins and porpoises have also been recorded around subsea structures (Todd et al. 2020). However, to date, few studies have focused on the role of these structures in relation to habitat use and movement by these species. Understanding megafauna habitat use around these structures may help inform future decommissioning options, aid in the understanding of marine connectivity between natural and artificial reefs, and ultimately aid in conservation and management efforts of endangered species such as the whale shark.
In this pilot study, we trialled acoustic telemetry around O&G infrastructure to assess its efficacy in a) identifying the timing and duration of visitations to these structures by megafauna species tagged in the region; b) understanding how megafauna may use these habitats; and c) assessing connectivity between these structures and natural habitats. Acoustic receivers were deployed around 4 oil & gas platforms and on 2 ROVS undertaking pipeline inspections on Australia’s Carnarvon Basin. Two whale sharks (Rhincodon typus) previously tagged in the World Heritage Ningaloo Reef Marine Park were detected at North Rankin A and Pluto (located between 350-340km north of Ningaloo). In a world first, we showed that acoustic telemetry can be used to: detect tagged whale sharks around oil and gas infrastructure; and that the detection patterns can help us understand how megafauna use these habitats.
Fig 2: A whale shark tagged with a Vemco V16 69 kHz acoustic transmitter (within dashed circle) pictured at Ningaloo Reef (picture by R.Pillans).