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Diel shifts and habitat associations of fish assemblages on a subsea pipeline
Abstract
Nocturnal studies of fish assemblages are relatively rare, particularly at depths greater than 100 m, despite the relevance of diel shifts in habitat usage to fisheries management. This study assesses fish diversity and abundance from remotely operated vehicle (ROV) video recordings that were collected by industry during the day and at night in the course of a subsea pipeline survey, at 130 m depth. A total of 34,862 fish from 41 species and 25 families were recorded along the 23 km of pipeline. The pipeline was characterised by a high abundance of commercially important snapper (Lutjanidae) and grouper (Epinephelidae) species. The fish assemblage sampled along the pipeline during the day differed markedly to that sampled at night time. Several ubiquitous predatory species, e.g. Epinephelus areolatus, Lutjanus quinquelineatus, Lutjanus russellii, where present during the day but not at night, likely moving off the pipeline to feed in nearby habitats. Structurally complex mesophotic epibenthic habitat forming invertebrates were observed on the pipeline including; mesophotic corals, crinoids (featherstars), gorgonocephalids (basket stars), hydroids, true anemones and sponges, but elsewhere in the region, historical trawling effort is thought to have removed such organisms and extensively modified the original habitat. These complex epibenthic habitats were considered to be important to commercial target species and the modification or loss of these habitats is thought to have negatively impacted the valuable commercial fisheries in the region. This study suggests pipelines can offer a significant epibenthic habitat and refuge for fish, potentially comparable to the historical habitats lost to trawling. Fish diversity and abundance was observed to be consistently greater where a gap/crevice existed beneath the pipeline and many species were frequently observed in conjunction with the complex invertebrate matrix above the pipeline, under spanning sections beneath the pipeline and at the pipeline-sediment interface, regardless of time of day. Further dietary analysis, spatially explicit fisheries modelling and off-pipeline surveys on the natural seafloor are required to further investigate the ecological value of pipelines and its influence in fish behaviour. The study builds knowledge of mesophotic coastal fish ecology and will help to inform discussions regarding the ecological and fisheries implications of decommissioning and the removal of subsea infrastructure.
... Each BRUV was baited with ~1 kg of crushed pilchards (Sardinops spp.) contained within a plastic-coated wire mesh bait bag, positioned 1.2 m in front of the camera. Sampling was undertaken during daytime hours (between at least 1 h after sunrise and completed at least 1 h before sunset) to record as many fish species and individuals as possible (Harvey et al. 2012a;Myers et al. 2016;Bond et al. 2018a). Each BRUV was left to record on the seafloor for a minimum of 60 min. ...
... The ROV survey took ~53 h, commencing at 23:30 on 18 February 2017 and concluding at 04:11 on 21 February 2017. Only video obtained during daytime hours (between 1 h after sunrise and 1 h before sunset) was comparable to BRUVs, because the abundance and species diversity of fish on a pipeline has been shown to change between night and day (Bond et al. 2018a). Consequently, only ROV video obtained between KP 0.680 and 5.540 was used in this study (i.e. a 4.6-km stretch of the pipeline). ...
... This work begins to address one of the suggestions from McLean et al. (2017) and Bond et al. (2018a) by providing the first method comparison in which BRUV and ROV video records were used to understand the fish assemblage associated with a subsea pipeline. Although the total number of species recorded using each method was the same (22 species) and no significant differences were detected in the total abundance of fish, each method recorded a significantly different fish assemblage at each site. ...
Context. Remotely operated vehicles (ROVs) are routinely used to inspect oil and gas infrastructure for industry’s operational purposes and scientists utilise this video footage to understand how fish interact with these structures.
Aim. This study aims to clarify how fish abundance data obtained from ROV video compares to that collected using baited remote underwater video (BRUV). Method. This study compares fish assemblages observed using an industry ROV and BRUVs along a pipeline located in 130-m water depth in north-west Australia.
Key results. Both methods recorded 22 species of fish, however each method observed 15 unique species. The fish assemblage recorded by each method was statistically different at all sites. Differences in the fish assemblages correlated with the caudal fin aspect ratio of each species: the mean caudal fin aspect ratio of fish recorded using BRUVs was 2.81, compared to
1.87 for ROV observations.
Conclusions. We interpret this to indicate differences in site attachment, with site-attached species having generally lower caudal fin aspect ratios that are associated with slower swimming speeds with a burst and glide pattern. Implications. Our results show that these remote video methods predominantly sample different fish assemblages and demonstrates how different sampling methods can provide different insights into fish interactions with subsea infrastructure.
... Epibenthic communities on pipelines are often identified by video footage from pipeline inspections and are characterised based on a standard classification scheme (Althaus et al., 2015). Flora and fauna most commonly found on pipelines include encrusting growth (typically coralline microalgae), black and octocorals, cnidarians, crinoids, echinoderms (basket stars and urchins), molluscs (bivalves), and sponges (Bond et al., 2018;McLean et al., 2020). In more complex habitat structures, many of these growth types will coexist forming complex invertebrate communities, which are often correlated to increased fish abundance (Bond et al., 2018). ...
... Flora and fauna most commonly found on pipelines include encrusting growth (typically coralline microalgae), black and octocorals, cnidarians, crinoids, echinoderms (basket stars and urchins), molluscs (bivalves), and sponges (Bond et al., 2018;McLean et al., 2020). In more complex habitat structures, many of these growth types will coexist forming complex invertebrate communities, which are often correlated to increased fish abundance (Bond et al., 2018). ...
... NORM-contaminated products in infrastructure may emit radiation that can penetrate pipeline material to irradiate nearby organisms (Fig. 3). These external-only radiation exposures may be an important exposure pathway as sessile organisms colonise subsea infrastructure to form artificial reefs which also provide habitat to fish and invertebrates (Bond et al., 2018). ...
Thousands of offshore oil and gas facilities are coming to the end of their life in jurisdictions worldwide and will require decommissioning. In-situ decommissioning, where the subsea components of that infrastructure are left in the marine environment following the end of its productive life, has been proposed as an option that delivers net benefits, including from: ecological benefits from the establishment of artificial reefs, economic benefits from associated fisheries, reduced costs and improved human safety outcomes for operators. However, potential negative impacts, such as the ecological risk of residual contaminants, are not well understood. Naturally occurring radioactive materials (NORM) are a class of contaminants found in some oil and gas infrastructure (e.g. pipelines) and includes radionuclides of uranium, thorium, radium, radon, lead, and polonium. NORM are ubiquitous in oil and gas reservoirs around the world and may form contamination products including scales and sludges in subsea infrastructure due to their chemistries and the physical processes of oil and gas extraction. The risk that NORM from these sources pose to marine ecosystems is not yet understood meaning that decisions made about decommissioning may not deliver the best outcomes for environments. In this review, we consider the life of NORM-contamination products in oil and gas systems, their expected exposure pathways in the marine environment, and possible ecological impacts following release. These are accompanied by the key research priorities that need to better describe risk associated with decommissioning options.
... Many of these pipelines have a small diameter, 12 in (305 mm) or less, and transport gas tens of kilometres, while others are up to 42 in (1066 mm) in diameter, connecting offshore fields to onshore processing facilities hundreds of kilometres away. Despite the prevalence of cyclones in the region, much of this pipeline infrastructure lies exposed on the seafloor, providing the opportunity for marine organisms to grow on it and mobile organisms to interact with it (McLean et al. 2017;Bond et al. 2018a). Similarly, commercial fishers can find the exposed pipelines using echo sounders, or locate many of them on marine charts. ...
... Two of these species, L. sebae and E. multinotatus, were in the top three species landed by commercial fisheries in the Pilbara in 2017 (Newman et al. 2019). These commercially valuable species are commonly associated with complex epibenthic invertebrate assemblages (Sainsbury et al. 1997;Newman 2002;Newman and Dunk 2003;Speare and Stowar 2007;Fitzpatrick et al. 2012;McLean et al. 2017), and are known to persist on pipelines in the PTMF (McLean et al. 2017;Bond et al. 2018a). Interrogation of VMS data show fishers target pipelines like Griffin and Echo Yodel most likely because they provide structurally complex habitat favourable for commercially valuable species. ...
... Traditional concepts suggest pipelines go through processes of scour, sagging, and backfilling and eventually self-bury at free-spans or for the entire pipeline (Sumer and Fredsøe 2002). Should this happen on the NWS, pipeline spans may reduce in length and height, and the cover of structurally complex marine growth may decrease, consequently impacting the abundance and species diversity of fish (McLean et al. 2017;Bond et al. 2018a). However, Leckie et al. (2015) described the mature state of a pipeline on the NWS as 'self-lowering' with a pseudostatic profile regularly alternating between buried and spanning. ...
Over 1400 km of oil and gas pipeline infrastructure exists within the boundaries of the Pilbara Trap Managed Fishery (PTMF) operating on the North West Shelf of Australia. Some of this infrastructure has reached the end of its operational life and requires decommissioning. Location and speed data collected from 2008 to 2018 using vessel monitoring systems onboard all trap fishing vessels (n = 3) operating in the PTMF were used to understand how fishing activity near pipelines has changed through time, and to identify the best predictive variables to explain hours spent fishing km−2 week−1. The proportion of fishing activity within 200 m of a pipeline increased over the survey decade and averaged 4.2% across all years. Hours spent fishing km−2 within 200 m of any pipeline was found to be 8.0 h km−2, ~ 11.4 times more than that recorded, on average, for the remaining area of the PTMF (0.7 h km−2), and ~ 4.6 times more than the western portion of the PTMP (1.7 h km−2) where all pipeline infrastructure exists. Fishing activity within 1 km of pipelines increased after their installation, and hence time since installation was the best predictor of fishing. This study demonstrated that trap fishers in the PTMF allocate a small proportion of their time targeting pipeline infrastructure, with the area close to a pipeline experiencing a relatively greater magnitude of fishing than that elsewhere in the PTMF. As such, the results of this study provide decision makers with an understanding of the intrinsic value of this infrastructure to trap fishers.
... Offshore oil and gas (O&G) infrastructure such as pipelines and platforms have proliferated along continental margins and in the deeper oceans worldwide (Ars and Rios, 2017). These structures are colonised by sessile and motile epibiota, which in turn attract fish and larger fauna (van der Stap et al., 2016;Bond et al., 2018;Thomson et al., 2018;McLean et al., 2019a;Todd et al., 2019). The role these structures play as artificial reefs has attracted greater attention worldwide as they age and as industry considers decommissioning options (Macreadie et al., 2011;Bull and Love, 2019). ...
... However, our data suggests that both whale sharks we detected moved away from the platform receivers at night. Diel movements of fish species driven mostly by feeding and reproduction are well known and the abundance of some fish around offshore infrastructure has been shown to decrease at night (Baggerman, 1980;Lowry and Suthers, 1998;Nagelkerken et al., 2000;Bond et al., 2018). In the Gulf of Mexico, Barker and Cowan (2018) found fish communities in surface waters around lit versus unlit platforms were most abundant during daylight hours, suggesting they utilised the structure during the day for shelter and had an aversion to the lights at night, potentially to avoid predation. ...
... In the Gulf of Mexico, Barker and Cowan (2018) found fish communities in surface waters around lit versus unlit platforms were most abundant during daylight hours, suggesting they utilised the structure during the day for shelter and had an aversion to the lights at night, potentially to avoid predation. On the NWS, predatory fish species that sheltered along pipelines during the day were absent at night, thought to be foraging in adjacent habitats (Bond et al., 2018). As the world's largest fish, the whale sharks we detected may be undertaking similar, nocturnal movements away from the platform, possibly using them as a refuge during the daylight hours. ...
Subsea infrastructure of the oil and gas industry attracts commercial fish species as well as megafauna including sea lions, turtles, sharks and whales. Potential impacts of this attraction, whether positive or negative, are unknown. As part of a pilot study, we deployed acoustic telemetry equipment around offshore infrastructure to assess its effectiveness in detecting tagged marine animals and to gain insights into patterns of megafauna occurrence around these structures. Acoustic receivers were placed around four oil and gas platforms and on two remotely operated vehicles (ROVs) on Australia’s North West Shelf. Two whale sharks ( Rhincodon typus ) tagged in the World Heritage Ningaloo Reef Marine Park were detected at two platforms, North Rankin A and Pluto, located up to 340 km to the northeast. The shark at North Rankin A was detected infrequently and only 15 times over ∼6 weeks. The shark at Pluto was detected each day of the 24-day deployment, in total 4,894 times. Detections at Pluto platform were highest during the day, with peaks at dusk and dawn. Our study indicates that acoustic telemetry around platforms may be an effective method for understanding how marine megafauna utilise these structures. We recommend collaborating with industry to undertake receiver detection range testing to understand the effectiveness of the method. Furthermore, future studies should co-occur with tagging programs at sites like Ningaloo Reef and around the structures themselves to maximise the probability of detecting animals at these sites, thereby improving our understanding of how marine megafauna interact with these structures.
... Subsea pipelines are an integral component of oil and gas operations and form extensive networks on the seafloor. Despite their prevalence in our oceans there are few environmental studies that assess the ecological role of subsea pipelines as habitat (although see [29][30][31][32][33][34], with the majority of literature focused on oil and gas platforms 14 . Research is now beginning to demonstrate the potential role subsea pipelines may serve in the marine environment. ...
... Studies that have assessed fish associations with subsea pipelines have either used existing industry remotely operated vehicle (ROV) video footage [31][32][33] , small submersibles 34 , or Baited Remote Underwater stereo-Video systems (stereo-BRUVs) 29,30 as a means of sampling. The use of a mini-ROV fitted with a stereo-video system (stereo-ROV) may be a more appropriate sampling approach for assessing fish associations on pipelines, as the stereo camera setup provides per unit area measurements of fish and accurate length data for biomass estimates in situ 12 . ...
... In total, eleven segments of exposed pipeline were surveyed with segment lengths varying between 0.3 and 1.7 km, which was dependent on the level of exposure of the pipeline. Pipeline surveys were completed between 08:30 and 17:00 h to minimise the effects of diel changes in fish behaviour on data collected 31,46 . Quantitative comparisons between the reef and soft sediment habitats were undertaken by dividing continuous footage of the pipelines into 50 m transects, with a minimum 20 m separation between transects to ensure independence. ...
Offshore decommissioning activities are expected to increase as oil and gas subsea infrastructure becomes obsolete. Decisions on decommissioning alternatives will benefit from quantifying and understanding the marine communities associated with these structures. As a case study, fish assemblages associated with an inshore network of subsea pipelines located on the North West shelf of Western Australia were compared to those in surrounding natural reef and soft sediment habitats using remotely operated vehicles fitted with a stereo-video system (stereo-ROVs). The number of species, the abundance, biomass, feeding guild composition and the economic value of fishes were compared among habitats. The community composition of fish associated with pipelines was distinct from those associated with natural habitats, and was characterised by a greater abundance and/or biomass of fish from higher trophic levels (e.g. piscivores, generalist carnivores and invertivores), including many species considered to be of value to commercial and recreational fishers. Biomass of fish on pipelines was, on average, 20 times greater than soft sediments, and was similar to natural reefs. However, the biomass of species considered important to fisheries recorded on the pipelines was, on average 3.5 times greater than reef and 44.5 times greater than soft sediment habitats. This study demonstrates that fish assemblages on the pipeline infrastructure exhibit high ecological and socioeconomic values.
... The use of oil and gas platforms as habitat by fish has been well-documented (e.g. Ajemian et al., 2015aAjemian et al., , 2015bClaisse et al., 2014;Friedlander et al., 2014;Gallaway et al., 2009;Love et al., 2006;Streich et al., 2017;Torquato et al., 2017), however, investigation of the habitat value of pipelines to fish assemblages has received less attention (although see; Bond et al., 2018a, Bond et al., 2018b, Bond et al., 2018cLove and York, 2005;McLean et al., 2017McLean et al., , 2020. Love and York (2005) reported that fish density was nearly six to seven times greater on pipelines compared to the adjacent seafloor in the Santa Barbara Channel, Southern California. ...
... In recent years, ROVs have emerged as an alternative approach for assessing fish assemblages, particularly on artificial structures (e.g. Ajemian et al., 2015b;Andaloro et al., 2013;Consoli et al., 2016;Trenkel et al., 2004), including pipelines (Bond et al., 2018a;McLean et al., 2017McLean et al., , 2020. ROVs are regularly used by the oil and gas industry to inspect subsea infrastructure, including pipelines, for inspection and maintenance purposes. ...
... We avoided concurrent sampling in the same area due to the possible influence of bait used to attract fish to the stereo-BRUVs affecting the stereo-ROV surveys. Surveys were done between 7:30 and 16:00 h to reduce diurnal variations in fish assemblages across the study (Bond et al., 2018a;Myers et al., 2016). Stereo-BRUVs surveys were completed over seven segments of exposed pipe, with four replicates deployed on each segment, where possible ( Fig. 1). ...
We compared and contrasted fish assemblage data sampled by baited remote underwater stereo-video systems (stereo-BRUVs) and stereo-video remotely operated vehicles (stereo-ROVs) from subsea pipelines, reef and soft sediment habitats. Stereo-BRUVs sampled greater fish diversity across all three habitats, with the stereo-ROV sampling ~46% of the same species on pipeline and reef habitats. Larger differences existed in soft sediment habitats, with stereo-BRUVs recording ~65% more species than the stereo-ROV, the majority of which were generalist carnivores. These differences were likely due to the bait used with stereo-BRUVs attracting fish from a large and unknown area. Fish may have also avoided the moving stereo-ROV, an effect possibly magnified in open soft sediment habitats. As a result of these biases, we recommend stereo-ROVs for assessing fish communities on pipelines due to their ability to capture fish in-situ and within a defined sampling area, but caution is needed over soft sediment habitats for ecological comparisons.
... Closeup imagery of epibenthic organisms that often form complex "marine growth" habitats on offshore structures is required, whereas for assessments of fish populations greater setback from the structure is necessary for abundance counts. Industry ROVs usually operate on a 24-h schedule, and on an "as-required" basis and as such their timing may bias observations, particularly abundance estimates for species that exhibit diel and/or seasonal changes in behavior and population dynamics (Barker and Cowan, 2018;Bond et al., 2018a). Once imagery is obtained from industry, further challenges can be faced in video formatting for photogrammetric analysis and in spatially linking video to specific infrastructure components. ...
... To facilitate accurate identification of fish, marine growth and other fauna, ROVs should collect at least HD video. Traditionally, industry ROV operations do not require collection of HD imagery and, as a result, analysis of historical imagery for science is hampered by difficulties in species identification and counting due to low image resolution (e.g., Bond et al., 2018a;McLean et al., 2018;Thomson et al., 2018). Most modern ROVs possess the ability to record HD imagery and should do so as TABLE 1 | Key environmental indicators for assessment and the approach for obtaining them using industry ROV. ...
... For example, typical ROV visual inspections of pipeline use multiple cameras to obtain a central, port and starboard view of the pipeline while an AUV usually uses a single, central camera. In this instance, the ability to see, identify and count fish that most often reside underneath or in the crevice between the seabed and pipeline (Bond et al., 2018a;McLean et al., 2018) is removed and the value of the survey for documenting fish populations significantly reduced. Potential limitations in data comparison should also be outlined to industry and rigorous method comparisons could be undertaken. ...
Remotely operated vehicles (ROVs) are used extensively by the offshore oil and gas and renewables industries for inspection, maintenance, and repair of their infrastructure. With thousands of subsea structures monitored across the world’s oceans from the shallows to depths greater than 1,000 m, there is a great and underutilized opportunity for their scientific use. Through slight modifications of ROV operations, and by augmenting industry workclass ROVs with a range of scientific equipment, industry can fuel scientific discoveries, contribute to an understanding of the impact of artificial structures in our oceans, and collect biotic and abiotic data to support our understanding of how oceans and marine life are changing. Here, we identify and describe operationally feasible methods to adjust the way in which industry ROVs are operated to enhance the scientific value of data that they collect, without significantly impacting scheduling or adding to deployment costs. These include: rapid marine life survey protocols, imaging improvements, the addition of a range of scientific sensors, and collection of biological samples. By partnering with qualified and experienced research scientists, industry can improve the quality of their ROV-derived data, allowing the data to be analyzed robustly. Small changes by industry now could provide substantial benefits to scientific research in the long-term and improve the quality of scientific data in existence once the structures require decommissioning. Such changes also have the potential to enhance industry’s environmental stewardship by improving their environmental management and facilitating more informed engagement with a range of external stakeholders, including regulators and the public.
... Fish that move between habitats transport nutrients, serving as nutrient sinks in the systems in which they feed and nutrient sources in the systems where their waste is excreted Shantz et al., 2015). Bond et al. (2018) described diel changes in the behaviour and relative abundance of fish on this pipeline, reporting a much higher relative abundance of Apogonidae (cardinal fishes), Epinephelus areolatus (areolate grouper), Lutjanus quinquelineatus (five-lined snapper) ...
... Moreover, the use of identical methods on and off pipeline avoids the difficulties, and potential confounds, faced by studies that compare fish populations using different assessment methods. Using stereo-BRUVs, we have provided information on the fish assemblage found on the pipeline, recording 26 species, of which 10 were not recorded from the most recent ROV survey by Bond et al. (2018). To date, a total of 48 species and 28 families of teleost fish and sharks have been recorded on the pipeline (Table S1) from this study and the 2013 ROV survey Bond et al., 2018). ...
... Using stereo-BRUVs, we have provided information on the fish assemblage found on the pipeline, recording 26 species, of which 10 were not recorded from the most recent ROV survey by Bond et al. (2018). To date, a total of 48 species and 28 families of teleost fish and sharks have been recorded on the pipeline (Table S1) from this study and the 2013 ROV survey Bond et al., 2018). A future challenge will be to reconcile data obtained by different survey methods (e.g. ...
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 × (11.14 SE) than in adjacent natural habitats (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.
... When these data are made available to researchers, new discoveries can be made, including a better understanding of fish associations with subsea infrastructure (e.g. McLean et al., 2017), marine growth estimates (van der Stap et al., 2016), new behavioural observations of animals (Gates et al., 2017a;Bond et al., 2018a) and, occasionally, even new species observations (Gates et al., 2017b). However, as the priority of industrial ROV operations is to inspect and maintain subsea infrastructure, rigorous scientific protocols are rarely applied in their operating procedures, which can limit inferences made from opportunistic use of this imagery. ...
... The difference may, in part, be due to sampling differences with Bond et al. (2018bBond et al. ( , 2018c utilising baited underwater cameras (stereo-BRUVs) rather than ROV video recordings. However, Bond et al. (2018a) and McLean et al. (2017) utilised ROV video records and still reported P. multidens to be ubiquitous on pipelines. We suspect that the difference may be due to their behaviour. ...
Scientists, industry and regulators are seeking to understand the influence of oil and gas infrastructure in our oceans to mitigate its impacts and maximise environmental benefits. This project equipped a standard work-class ROV with a light-weight stereo-video camera system to collect high definition imagery of fish and habitats formed by marine growth associated with Woodside Energy's Goodwyn Alpha Platform jacket (GWA) 138 km offshore of Dampier, north-west Australia. ROV video surveys were rapidly performed by industry on four faces of the GWA jacket, from the surface to the seabed at 130 m, yielding 1 h and 14 min of imagery. The stereo-video cameras continued to film during standard ROV operations collecting a further 150 h of HD imagery, used to build a comprehensive fish species list. A total of 8676 individual fish from at least 57 species and 20 families, with an estimated combined mass of 8719 kg, were recorded from the vertical transects of four faces of the jacket. An additional 43 fish species from 21 families were recorded via rapid assessment of a subset of the additional, standard ROV operations imagery. The jacket was characterised by abundant Caranx sexfasciatus (bigeye trevally), Pseudanthias spp. (basslets), Heniochus diphreutes (schooling bannerfish), Labridae sp. (wrasse) and Acanthurus spp. (surgeonfish). Several fish important to the demersal scalefish fishery in the region were observed, including: Lutjanus argentimaculatus (mangrove jack), Lutjanus erythropterus (crimson snapper), Lutjanus malabaricus (saddletail snapper), Lutjanus russellii (Moses' snapper). Eleven broad marine growth types were observed with encrusting/enveloping species (brown algae, filamentous mat, coralline algae, calcite) and hard corals (Tubastrea sp.) present in the greatest coverage. Both marine growth and fish assemblages changed markedly with depth. The addition of a lightweight stereo-video system to an industrial ROV and the allocation of short amounts of time for rapid vertical surveys provided important information on the ecology of an oil and gas platform jacket. Future industrial ROV campaigns should consider utilising this approach to gather scientific information that may have value in the context of decommissioning comparative assessments and, more generally, improves our understanding of the impact of oil and gas infrastructure in our oceans.
... In depths >40 m, the fish assemblage on the pipeline was characterised by large bodied, commercially important species including P. multidens, L. malabaricus, L. russellii, L. sebae and A. spinifer. These species are commonly associated with structurally complex epibenthic invertebrate communities that include sponges and octocorals [15,16,[60][61][62][63][64]. These habitats were once common throughout the north-west shelf region, but were reduced by trawl fishing activities between 1959 and 1990 [16]. ...
... To understand why certain fish associate with pipelines, it may be necessary to investigate the epibenthic invertebrates colonizing O&G pipelines, and the habitat that they create. Comparable studies examining fish assemblages on pipelines on the north-west shelf found a high diversity of fish at 60-80 m depth and 120-130 m depth using ROV footage [15,60]. Fish diversity was positively correlated with invertebrates such as sponges and crinoids growing on the pipeline, providing a complex habitat for fish assemblages [15]. ...
Knowledge of marine ecosystems that grow and reside on and around subsea oil and gas infrastructure is required to understand impacts of this offshore industry on the marine environment and inform decommissioning decisions. This study used baited remote underwater stereo-video systems (stereo-BRUVs) to compare species richness, fish abundance and size along 42.3 km of subsea pipeline and in adjacent areas of varying habitats. The pipeline is laid in an onshore-offshore direction enabling surveys to encompass a range of depths from 9 m nearshore out to 140 m depth offshore. Surveys off the pipeline were performed across this depth range and in an array of natural habitats (sand, macroalgae, coral reef) between 1 km and 40 km distance from the pipeline. A total of 14,953 fish were observed comprising 240 species (131 on the pipeline and 225 off-pipeline) and 59 families (39 on the pipeline and 56 off-pipeline) and the length of 8,610 fish were measured. The fish assemblage on and off the pipeline was similar in depths of <80 m. In depths beyond 80 m, the predominant habitat off-pipeline was sand and differences between fish assemblages on and off-pipeline were more pronounced. The pipeline was characterised by higher biomass and abundances of larger-bodied, commercially important species such as: Pristipomoides multidens (goldband snapper), Lutjanus malabaricus (saddletail snapper) and Lutjanus russellii (Moses’ snapper) among others, and possessed a catch value 2–3 times higher per stereo-BRUV deployment than that of fish observed off-pipeline. Adjacent natural seabed habitats possessed higher abundances of Atule mate (yellowtail scad), Nemipterus spp. (threadfin bream) and Terapon jarbua (crescent grunter), species of no or low commercial value. This is the first published study to use stereo-BRUVs to report on the importance of subsea infrastructure to commercially important fishes over a depth gradient and increases our knowledge of the fish assemblage associated with subsea infrastructure off north-west Australia. These results provide a greater understanding of ecological and fisheries implications of decommissioning subsea infrastructure on the north-west shelf, and will help better inform decision-making on the fate of infrastructure at different depths.
... Fish that move between habitats transport nutrients, serving as nutrient sinks in the systems in which they feed and nutrient sources in the systems where waste is excreted Shantz et al., 2015). Bond et al. (2018) suggested that many fish species likely move off subsea pipelines at night to feed and return by day for shelter. For wellheads, Pradella et al. (2014) also noted the absence of many species at night at the structures. ...
... Previous fish research in depths 80-200 m on the NWS of Western Australia is limited to studies on pipelines Bond et al., 2018), wellheads (Fowler et al., 2012;Pradella et al., 2014;Fowler et al., 2015), specific research trawl expeditions and data reported by commercial fisheries operations (e.g. Newman et al., 2015). ...
When production ceases, offshore oil and gas wells are taken out of service which involves safely plugging, abandoning and usually removing most of the associated subsea equipment. This process must consider impacts to marine ecosystems to meet regulatory requirement and for best environmental practice. However, there is a paucity of information globally on the ecosystem value of these structures, despite the many thousands that are installed throughout our oceans. This study provides the first assessment of fish assemblages and habitats formed by colonising invertebrates on oil and gas wellheads and associated infrastructure in depths of 78–825 m on the north west shelf of Western Australia. Video footage was obtained from Remotely Operated Vehicles deployed by industry on 25 wellhead structures, with six surveyed in each of four distinct depth zones: 78–85 m, 125–135 m, 350–395 m and 490–550 m, and one in 825 m depth. A total of 7278 individual fish from 60 species and 35 families were observed. Commercially important lutjanid (snapper) and epinephelid (grouper) species were common and most abundant on well infrastructure to depths of 135 m, but were absent in depths > 350 m. An as yet unidentified species of roughy, recorded here as Gephyroberyx sp. was the most common fish species observed on well infrastructure in depths > 350 m. Two speckled swellsharks (Cephaloscyllium speccum), believed to be endemic to north-west Australia, were observed for the first time in situ. Numerous fish species were observed at depths beyond their known limits and two IUCN vulnerable species were recorded: the grey nurse shark (Carcharias taurus; 135 m depth) and the round ribbontail ray (Taeniura meyeni; 78 m depth). Fish assemblages and colonising invertebrate habitats present on wellheads and associated infrastructure were strongly influenced by depth, age and height of the structures. Older, taller wellheads in depths < 135 m possessed greater abundances of groupers, snappers, site-attached reef species, and transient pelagic fish species. Beyond 350 m depth, the number of species and total fish abundance declined markedly, as did the percent cover of ascidians, black/octocorals, sponges and Gorgonocephalidae (basket stars) observed growing on the infrastructure. Deeper structures were characterised by an abundance of Gephyroberyx sp. and, while these structures had less colonising invertebrate coverage in general, crinoids (490–550 m) and crustacea (barnacles; 350–395 m) were dominant at these depths. With very little known about marine ecosystems in depths > 100 m, or about wellheads as a type of subsea structure, this study demonstrates the ecological value of ROV footage obtained during industry operations and is indicative of the importance of subsea oil and gas infrastructure as a habitat for fish, and potentially as structures with value to fisheries.
... The presence or introduction of any novel and structurally complex habitat within the ocean often increases the local abundance, biomass and diversity of marine organisms (Castro et al., 2002), often referred to as artificial reefs or fish aggregating devices. Research on the ecological influence of O&G structures demonstrated that they could facilitate larval settlement and recruitment (Gass and Roberts, 2006;Love et al., 2006;Nishimoto et al., 2019), enhance local productivity and biomass (Todd et al., 2009;Meyer-Gutbrod et al., 2019;Clausen et al., 2021), and increase biodiversity of fish, invertebrates, and megafauna (McLean et al., 2017;Bond et al., 2018a;Broadbent et al., 2020;Todd et al., 2020). In seascapes where natural hard substrate is scarce, O&G structures can act as artificial reefs by providing a new physical habitat for organisms to colonize, and novel marine ecosystems to develop (Friedlander et al., 2014;van Elden et al., 2019). ...
... ROV speed did change in some instances, particularly in the shallow sections of platforms where swells affected ROV stability and water visibility. ROV speed was maintained at ca. 0.5 m -1 , with data collected only during daylight hours which removed any diel effect of detectability on biomass and production calculation for these species, due to differing patterns of behaviour (Lowry and Suthers 1998;Ley and Halliday 2007;Bond et al., 2018b). ...
... ROVs are now intensively applied in various fields such as the sea oil industry for the purpose of infrastructure installation, device maintenance and repair, and pipeline inspection, etc. [7][8][9]. In science research activities, many researchers [10][11][12][13][14][15] have also used ROVs to accomplish inspection and sampling tasks like scanning seabed geomorphy and submarine biosampling in the deep-sea environment. ...
Remotely operated underwater vehicles (ROVs) have been widely used in deep-sea resource exploitation and industrial engineering operations. To perform these tasks accurately in the deep-sea environment, stable motion control has become a key area of research on ROV systems, which has led to the importance of analyzing the hydrodynamic characteristic of ROVs. But a systematic methodology for analyzing the hydrodynamic characteristics of ROVs is still lacking nowadays. In this paper, systematic numerical simulation methods for analyzing hydrodynamic characteristics and shape optimization of a work-class ROV are conducted, and details of simulation procedures based on computational fluid dynamics are studied, which can be a foundation for robust controller design.
... One possible option currently being explored in Australia is to decommission in situ, whereby certain parts of the infrastructure are left on the seabed. Previous studies have demonstrated the benefits of decommissioning in situ through the provision of artificial reefs that increase biodiversity and improve ecosystem connectivity (McLean et al. 2017(McLean et al. , 2022Bond et al. 2018;Fowler et al. 2018). However, few studies to date have assessed the potential risks due to contaminants associated with the infrastructure (MacIntosh et al. 2021;Melbourne-Thomas et al. 2021;Koppel et al. 2022). ...
In the coming years, the oil and gas industry will have a significant liability in decommissioning offshore infrastructure such as subsea pipelines. The policies around decommissioning vary depending on regional policies and laws. In Australia, the ‘base case’ for decommissioning is removal of all property and the plugging and abandonment of wells in line with the Offshore Petroleum and Greenhouse Gas Storage (OPGGS) Act 2006. Options other than complete removal may be considered where the titleholder can demonstrate that the alternative decommissioning activity delivers equal or better environmental outcomes compared to complete removal and meets all requirements under the OPGGS Act and regulations. Recent research has demonstrated that decommissioning in situ can have significant environmental benefits by forming artificial reefs, increasing marine biodiversity, and providing a potential fishery location. An issue, which has been given less attention, is around contaminants remaining within decommissioned infrastructure and their potential risks to the marine environment. Mercury is a contaminant of concern known to be present in some oil and gas pipelines, but the potential long-term impacts on marine ecosystems are poorly understood. We present a synthesis of information on mercury cycling in the marine environment including key drivers of methylation in sediments and ocean waters, existing models to predict methylmercury concentrations in sediments, and toxicological effects to marine biota. We discuss the applicability of existing water and sediment quality guidelines, and the associated risk assessment frameworks to decommissioning offshore infrastructure contaminated with mercury. Globally, research is needed to provide a comprehensive risk assessment framework for offshore infrastructure decommissioning. We recommend future areas of research to improve our understanding of the potential risks associated with mercury in subsea oil and gas pipelines.
... These effects may vary over time, relating to environmental conditions and stage of ecological succession (Fujii, 2015;Gates et al., 2019;Todd et al., 2019). Consequently, artificial structures have a potential role in restoring degraded marine ecosystems such as coral reefs (Rinkevich, 2014), mollusc reefs (Walles et al., 2016), algal forests (Gianni et al., 2013) and historically trawled or degraded habitats (Bond et al., 2018a), and have been proposed for restoration of disturbed deep-sea habitats (Cuvelier et al., 2018). ...
Large structures are introduced into deep-water marine environments by several industrial activities, including hydrocarbon exploitation. Anthropogenic structures can alter ecosystem structure and functioning in many marine ecosystems but the responses on continental margins are poorly known. Here, we investigate the short-term response of benthic megafauna to the installation of a 56 km-long 30 cm diameter pipeline on the Angolan Margin (Block 31) from 700 to 1800 m water depth using remotely operated vehicle imagery. Clear depth-related patterns exist in the density, diversity and community structure of megafauna observed in 2013 prior to pipeline installation. These patterns are altered in a subsequent survey in 2014, three-months after pipeline installation. Significant increases in density, particularly in mid-slope regions are observed. Diversity is generally, but not consistently, enhanced, particularly in the shallower areas in 2014. Clear changes are noted in community structure between years. These changes are primarily caused by increases in the abundance of echinoderms, particularly the echinoid Phormosoma sp. indet. There was no evidence of colonisation of the pipeline in three months by visible fauna. The few large anemones observed attached to the pipe may be able to move as adults. The pipeline appeared to trap organic material and anthropogenic litter, and may enhance available food resources locally as well as providing hard substratum. These results indicate complex and ecosystem-dependent responses to structure installation and caution against simplistic approaches to environmental management.
... Subsea pipelines associated with offshore oil and gas production vary in their ecological outcomes. The diversity and abundance of fishes is often higher on pipelines than on surrounding natural habitat (McLean et al. 2017;Bond et al. 2018b), and sessile organisms such as octocorals and sponges are found in higher density on pipelines (Bond et al. 2018a;Rouse et al. 2019). Pipelines also create obstacles to commercial trawling activity, providing protection to benthic communities as well as target and non-target fish species (de Groot 1982). ...
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.
... Accounting for collinear variables is important for model stability and was especially important in our study because we had multiple correlated explanatory variables ( Figure A.2). The full-subsets approach was developed for ecological applications and has great utility for evaluating the influence of correlated environmental factors on the ecology of biota (McLean et al. 2016;Bond et al. 2018). We used the R package FSSgam 1.11 (Fisher et al. 2018) to generate the best-fitting model(s) for each ocean age year. ...
An improved understanding of the mechanisms influencing productivity of fish populations is critical for accurately determining harvest rates and identifying years of conservation concern. Here we reconstruct yearly scale growth of three Puget Sound (PS) Chum Salmon Oncorhynchus keta stocks over 16 brood years (1997–2012) to better understand how variation in marine growth may be related to environmental factors, intra‐ and interspecific competition, and stock productivity. Generalized additive mixed models identified copepod species richness in the northern California Current and the abundance of PS Pink Salmon O. gorbuscha and Chum Salmon as strong predictors of first‐year growth, the latter indicative of density‐dependent effects as the abundance of local competitors (Pink and Chum salmon) increased. Second‐year growth was negatively related to the Aleutian Low–Beaufort Sea Anticyclone (ALBSA), a recently defined metric of the Aleutian Low, and showed a nonlinear positive to negative relationship with sea surface temperature in the Gulf of Alaska. Puget Sound Chum and Pink Salmon abundances were also significantly related to second‐year growth but did not suggest density‐dependent effects like those observed in ocean year 1. Third‐year growth was closely related to large‐scale climate indicators, demonstrating a nonlinear negative to positive relationship with the North Pacific Gyre Oscillation, a negative relationship with ALBSA, and a negative relationship with North Pacific Pink Salmon abundance when catch statistics indicated that abundance was high. Models indicated that PS Chum Salmon stock productivity (recruits per spawner) was positively correlated with back‐calculated first‐year growth and negatively correlated with second‐ and third‐year growth, suggesting that for brood years whose surviving adults experienced rapid early marine growth, there were cohort survival benefits. As new relationships between large‐scale indicators and Pacific salmon stocks are identified, incorporating these indicators into forecasting efforts is paramount for effective and sustainable management of fishery resources.
... Offshore oil and gas (O&G) infrastructure provides habitat that can promote biodiversity (Love and York 2005;Bond et al. 2018a;McLean et al. 2017McLean et al. , 2019Todd et al. 2020) and enhance fish production (Smith et al. 2016;Claisse et al. 2019), particularly in environments that are oligotrophic or where natural hard substrates (e.g. reefs) are limited. ...
An assessment to remove, partially remove, leave in situ or repurpose oil and gas infrastructure at end of field life can be more robust if it uses rigorous, relevant and accurate data. We used industry remotely operated vehicle (ROV) video, specialised high-definition stereo-video systems and partnered with industry to enhance future ROV campaigns for the collection of scientific data from infrastructure. Data from 17 pipelines and 51 wells were analysed to report on patterns in fish species richness and abundance in Australia’s north, north-west and south-east regions. This represents the largest synthesised data set on marine communities for pipelines and wells, globally. We observed 401 fish species, 350 along pipelines and 113 on well infrastructure. Potential new fish species, critically endangered species, unique behaviours and diverse communities were discovered around pipeline and well infrastructure. Predicting the environmental consequences of different decommissioning options relies on a region-specific understanding of the ecological communities that are associated with these structures. We showcase marine research from around Australia that will inform local decommissioning and contribute to a more comprehensive global understanding of the impact of subsea infrastructure in our oceans.
... com)]. Archival footage is better suited to quantify fish biodiversity (Bond et al., 2018a;McLean et al., 2021). Although, research questions formulated by experts and other stakeholders (Shaw et al., 2018) encompass many themes that are important to make informed decisions (Figure 1), those themes, do not get reflected in the research that has been carried out to date, aside from biodiversity assessments. ...
Numerous oil and gas (O&G) installations worldwide will need to be decommissioned in the near future. Complete removal of subsea structures is often the default approach although some regions retain structures under rigs-to-reefs programs. Here, we reviewed the published literature to understand the status of global research on decommissioning, and specifically identify gaps in ecological knowledge. We estimated the frequency of different research categories (i.e., themes, and spatial/temporal scales), and tested the assumption that the number of papers across the categories of each research aspect was even in distribution. However, the frequency of studies focusing on biodiversity at a local (≤100 km²) scale (relative to regional and oceanic and pan-oceanic scales) were significantly higher; while other theme categories (e.g., eco-toxicology, connectivity, structural-integrity, restoration and other) were significantly lower than expected. Temporally, ≤1-year studies were more frequent than multi-year studies, but these frequencies did not significantly deviate from the assumed distribution of equal frequencies. We propose that further research be carried out to evaluate the benefits of both retention and removal of structures. Ecological research on decommissioning should extend its focus beyond biodiversity, to include eco-toxicology, structural-integrity, connectivity at larger spatial and temporal scales. This would provide a more holistic assessment of ecological impacts to inform sustainable and equitable development choices in multiple Blue Economy sectors, as we transition from offshore O&G to marine renewables.
... Offshore oil platform placement and well drilling, submarine pipelaying, and coastal port and refinery construction can mobilize marine sediments and disturb benthic organisms [65,66], resulting in permanent loss of physical habitat and mobilization of contaminants into marine food webs [121]. Coastal oil ports and refineries result in permanent shoreline alteration and loss of productive nearshore habitats such as mangroves, seagrass beds, estuaries, and kelp forests which serve as critical habitats for early life stages of many commercially valuable fishes and invertebrates-serving to increase mortality and potentially decrease fishery productivity. ...
A quarter of global oil production comes from offshore fields and about 60% of internationally-traded oil travels by tankers. The relationship between oil, fisheries, and coastal communities is documented primarily through case studies in individual jurisdictions and via the impacts of oil spills. Yet, the implications of oil development for fisheries and coastal communities are much broader. This study provides an extensive review of the effects of oil development in relation to four interconnected themes: 1) the environment, including marine habitats and fish; 2) small-scale fisheries and coastal community livelihoods; 3) coastal and ocean spaces, including disputes over territory and infrastructure; and 4) ocean and coastal governance processes. We map spatial overlaps between the oil sector and small-scale fisheries and point to the frequent displacement of fishers from fishing grounds due to increasing coastal traffic and infrastructure, and the catastrophic effects of oil spills on fisheries and coastal economies. Though the oil sector generally has negative impacts on fisheries livelihoods and coastal communities, these effects and their mechanisms vary across locations, ecosystems, species, and specific activities and groups. Overall, this narrative review provides a comprehensive account of the scholarship to date and points to key themes for future research, including intersections between offshore oil and gender, cross-sectoral governance, and the achievement of Sustainable Development Goal 14. Underpinning all of these challenges and potential solutions is a clear need for stronger integration of social and natural science knowledge, perspectives, and tools.
... Higher diversity and abundance of fish occurs on pipelines that feature spanning (gap between pipeline and seafloor) than on pipelines that rest directly on the seafloor or are part buried . Similarly, fish are more diverse and abundant on pipelines that have been colonised by habitat-forming species such as sponges and corals (Bond et al., 2018b;McLean et al., 2017). These habitats likely offer a significant food source and refuge for fish, but also for invertebrates upon which fish feed Rouse et al., 2019). ...
The value of subsea pipelines as habitat for fish and benthic species is being considered, particularly by the oil and gas industry as they look to decommission seafloor infrastructure reaching the end of production. We investigated fish and benthic communities along a ca.345 km section of offshore pipeline in remote northern Australia to compare pipeline communities with those in surrounding areas and provide context for decommissioning risk assessments. We surveyed pipeline and adjacent natural seabed ecosystems at five locations on the continental shelf using remote video technology to quantify fish and benthic communities and modelled predicted fish communities across the study locations. We found that the pipeline supported turfing and low-relief biota (e.g. coralline algae, ascidians, bryozoans, small/encrusting sponges and soft coral or mixed filter feeder communities) with cover >75%. Pipeline benthic communities differed from those in adjacent ecosystems. Within 6 km of the pipeline, the seabed was predominantly sand/silt with only sparse biota; natural hard substrate (e.g. shoal features within 3 km of the pipeline) supported diverse coral and filter feeder communities (average 10–25% cover). Fish abundance and assemblage composition on the pipeline also differed from those in surrounding high- and low-complexity habitats. This difference was driven by high abundance and biomass of commercially important fish species near the pipeline and sand-affiliated species elsewhere. Our study provides important new insights into the marine communities associated with a subsea pipeline in northern Australia; with this artificial habitat observed to support a subset of species known to inhabit the area, but effectively representing a unique assemblage within the region.
... However, there also exists oil and gas ROV engineering surveys of platforms and associated infrastructure (i.e., pipelines, subsea equipment and wellheads) conducted as part of routine physical integrity inspections. In the past few years, researchers off western Australia [8][9][10][11][12] and in the North Sea [13,14] have begun to use this archival footage to characterize the biological communities associated with the offshore oil and gas structures. ...
Offshore oil and gas platforms have a finite life of production operations. Once production ceases, decommissioning options for the platform are assessed. The role that a platform’s jacket plays as fish habitat can inform the decommissioning decision. In this study, conducted along the crossbeams of a California platform jacket and using an ROV, we compared estimates of fish diversity and densities determined from a targeted “biological” survey with those from a replicated “structural” survey. We found that the water column fish species assemblages characterized by the two methods were similar. By contrast, the two survey methods yielded different species assemblages inhabiting the crossbeam at the platform jacket base. This difference occurred because, at least off California, the platform jacket base species diversity tends to be highest where the bottom crossbeam is undercut, creating sheltering sites for many species. Because the structural method inadequately imaged the seafloor-crossbeam interface, particularly where a gap occurred between crossbeam and seafloor, substantial numbers of fishes were not visible. While we cannot extrapolate from this study to all platforms’ worldwide, it is clear that routine platform structural integrity surveys may be a valuable source for opportunistic marine community surveys. Intentional planning of the structural survey to incorporate relatively minor variations (e.g., maintaining fixed ROV distance from the infrastructure and consistent 90° camera angle) coupled with a deliberate consideration of the platform ecology (e.g., positioning the ROV to capture the seafloor-crossbeam interface) can substantially improve the effects on fish assemblage assessments from routine structural surveys without compromising the integrity assessment. We suggest that these biases should be both acknowledged and, understood when using routine structural surveys to inform platform ecology assessment. Additional consideration may be given to structural surveys that incorporate incremental adjustments to provide better data applicability to biological assessments.
... Multiple stereo-BRUVs can be deployed concurrently, with ~10 stereo-BRUV systems providing optimum logistical efficiency for 60-minute deployment times. Crepuscular periods should be avoided due to demonstrated changes in fish behaviour during these times (Myers et al. 2016;Bond et al. 2018a). When sampling in low light conditions, both blue (450-465 nm) and white (550-560 nm) lights can be used. ...
Baited remote underwater stereo‐video systems (stereo‐BRUVs) are a popular tool to sample demersal fish assemblages and gather data on their relative abundance and body size structure in a robust, cost‐effective and non‐invasive manner. Given the rapid uptake of the method, subtle differences have emerged in the way stereo‐BRUVs are deployed and how the resulting imagery is annotated. These disparities limit the interoperability of datasets obtained across studies, preventing broadscale insights into the dynamics of ecological systems.
We provide the first globally accepted guide for using stereo‐BRUVs to survey demersal fish assemblages and associated benthic habitats.
Information on stereo‐BRUVs design, camera settings, field operations and image annotation are outlined. Additionally, we provide links to protocols for data validation, archiving and sharing.
Globally, the use of stereo‐BRUVs is spreading rapidly. We provide a standardized protocol that will reduce methodological variation among researchers and encourage the use of Findable, Accessible, Interoperable and Reusable workflows to increase the ability to synthesize global datasets and answer a broad suite of ecological questions.
... It is possible that circles exist along the EY pipeline, but are out of view, beyond the irregular and steep-sloped depressions which induce disruptions and variation in seafloor hydrodynamics. In addition, fish in general are more abundant where pipeline spans exist (Bond et al., 2018;McLean et al., 2017) which may deter pufferfish from building nests due to egg disturbance or predation. The extent of any such potential effect, however, remains unknown, as only a thin strip of seafloor centred on the umbilical and pipeline was surveyed. ...
In 2011, the enigma of “mystery circles,” small but complex underwater structures first observed by divers from southern Japan in 1995, was solved when a new species of pufferfish, white‐spotted pufferfish (Torquigener albomaculosus Matsuura 2014), was identified as the responsible agent. To date these circles have been described only from Japan, where they are formed on a sandy seafloor in water depths less than 30 m. A survey of oil field infrastructure on the North West Shelf of Western Australia in 2018 using a remotely operated vehicle and hybrid autonomous underwater vehicle (HAUV) recorded a high‐resolution video and bathymetric data of 21 circular formations with similar features to those described in Japan. The circles display dimensions and morphology like those described from Japan, but were observed in water depths between 129 and 137 m. The HAUV also recorded high‐resolution photographs which captured a Torquigener sp. fish in the immediate vicinity of the circles. An additional circle and Torquigener sp. were observed in images collected by baited remote underwater stereo‐video in a nearby location in 129 m depth. These circles are the first to be found in Australia. The pufferfish species responsible cannot be identified from images collected. Such a discovery not only generates intrigue and wonder among scientists and the general public but also provides an insight into the reproductive behaviour and evolution of pufferfish globally.
... In recent years, many researchers (Benfield et al., 2019;Bond et al., 2018;Corbera et al., 2019;Macreadie et al., 2018;Raoult et al., 2020;Wetz et al., 2020) used ROV devices for samplings, explorations, measurements and recording high quality images and videos. Capocci et al. (2017) categorized the underwater vehicles and investigated the difference between the mid-sized inspection-class and the handheld ROVs. ...
Nowadays, remotely operated vehicle (ROV) is an integral part of the marine industry. In this study, the hydrodynamic performance of a specific model of ROV is evaluated by numerical and experimental simulations in different Reynolds numbers ranging from 39291 to 157163 and various angles of attack from 0° to 45°. Moreover, two rectangular cubic models with fillet and sharp edges are modeled for comparative study. The wind tunnel and the finite volume methods are used for experimental and numerical simulations, respectively, and the Menter's SST k-ω model is employed to simulate the turbulent flow. The leading edge geometry, angle of attack, and Reynolds number are found to be the most effective factors on the drag forces. Additionally, the fillet edge model had better hydrodynamic performance than the ROV and the sharp edge rectangular cubic model considerably.
... There are over 12 000 oil and gas platforms around the world, many of which have been in place for decades (Ars and Rios 2017). Over this time, the sub-surface infrastructure of these platforms is colonised by sessile marine organisms such as algae, corals and sponges, which provide habitat and food for a variety of marine fauna (Forteath et al. 1982). ...
Many offshore oil and gas platforms around the globe are reaching their end-of-life and will require decommissioning in the next few decades. Knowledge on the ecology of offshore platforms and their ecological role within a regional context in Australia is limited and the subsequent consequences of decommissioning remain poorly understood. Remotely operated vehicle (ROV) video is often collected during standard industry operations and may provide insight into the marine life associating with offshore platforms; however, the utility of this video for scientific purposes remains unclear. We propose a standardised method of analysing this large database of archival ROV footage with specific interest in analysing the vertical distribution of fish species. Baited remote underwater video systems (BRUVS) are a widely used tool for studying marine faunal communities, and we demonstrate the value of BRUVS for understanding the regional ecology around offshore platforms. A combination of BRUVS and ROV data can be used to determine the relative ecological value of offshore platforms within a regional context. The Wandoo oil platform on Australia’s North West Shelf was used as a case study to test these proposed methods by assessing demersal and pelagic fish populations both on and around the Wandoo platform and various natural habitats in the region.
... Most individuals of the species L. russellii were detected in the mangroves and coral reefs, and this multiple habitat use reflects a relaxed day-night shift, with individuals feeding in seagrass beds at night and shifting to sheltered areas (mangrove/ coral reefs) by daytime (Nagelkerken et al., 2000a;Bond et al., 2018). Upeneus tragula and Sillago maculata utilized almost all habitats. ...
The length‐weight relationships (LWRs) were studied for eight seagrass fish from Wenchang, China, using gill nets (150*1 m, mesh size 0.5 cm), including Gerres oblongus, Ambassis kopsii, Halichoeres nigrescens, Sillago aeolus, Yongeichthys criniger, Oxyurichthys tentacularis, Lethrinus haematopterus and Hypoatherina tsurugae, in November 2017, March and August 2018. Results suggest that mean LWR parameters b for these eight seagrass fish varied from 2.801 for L. haematopterus to 3.640 for A. kopsii, and r2 valued from .950 for L. haematopterus to 0.993 for H. nigrescens. This study will help us to better understand the ecological parameters these seagrass fish.
... Our experiments were conducted during the day when many reef fishes are known to use coral reefs as refuge from predators (Rasher et al. 2017;Bond et al. 2018). In addition to this spatial refuge from predation, prey species can alter their behaviours to avoid exhibiting "risky" behaviours when predators are active, creating temporal refugia from predation (Smith et al. 2019). ...
Predators can exert strong ecological effects on their prey either via consumption or by altering their behaviour and morphology. In marine systems, predators and their prey co‐occur in a three‐dimensional environment, but to date predator–prey studies have largely focussed on behaviours of prey on horizontal (distance from shelter) rather than vertical (height in water column) axes. We used life‐size shape‐models of a blacktip reef shark Carcharhinus melanopterus (threatening shape‐model), a juvenile coral trout Plectropomus leopardus (non‐threatening shape‐model) and a shape‐control to examine the impact of perceived instantaneous (measured by time to first feeding) versus sustained (measured by time to consume the entire bait) predation threats on the feeding behaviour and three‐dimensional use of space by mesopredatory reef fishes in a coral reef environment. We found that mesopredatory fishes such as red snapper Lutjanus bohar and spangled emperor Lethrinus nebulosus took longer to begin feeding and to consume predation assays (fish baits) at greater distances from the shelter of a patch reef across both horizontal and vertical axes and that this phenomenon was stronger in the vertical axis than the horizontal. The presence of a life‐size shape‐model of a shark, which we used to increase the perception of predator threat, magnified the instantaneous effect compared to non‐threatening models, but not the sustained effect. We found no evidence for a difference in the level of predation risk posed by the shape‐model of the juvenile coral trout (a non‐threatening reef fish) and a negative control (no shape‐model). Our study suggests that mesopredators modify their behaviours in response to the perceived risk of predation across both horizontal and vertical axes away from shelter, and that this response is most severe on the vertical axis, potentially limiting daytime foraging behaviour to a hemisphere around shelter sites.
... Most individuals of the species L. russellii were detected in the mangroves and coral reefs, and this multiple habitat use reflects a relaxed day-night shift, with individuals feeding in seagrass beds at night and shifting to sheltered areas (mangrove/ coral reefs) by daytime (Nagelkerken et al., 2000a;Bond et al., 2018). Upeneus tragula and Sillago maculata utilized almost all habitats. ...
Understanding the connectivity of fish among different typical habitats is important for conducting ecosystem-based management, particularly when designing marine protected areas (MPA) or setting MPA networks. To clarify of connectivity among mangrove, seagrass beds, and coral reef habitats in Wenchang, Hainan Province, China, the fish community structure was studied in wet and dry seasons of 2018. Gill nets were placed across the three habitat types, and the number of species, individuals, and body size of individual fish were recorded. In total, 3 815 individuals belonging to 154 species of 57 families were collected. The highest number of individuals and species was documented in mangroves (117 species, 2 623 individuals), followed by coral reefs (61 species, 438 individuals) and seagrass beds (46 species, 754 individuals). The similarity tests revealed highly significant differences among the three habitats. Approximately 23.4% species used two habitats and 11.0% species used three habitats. A significant difference (p<0.05) in habitat use among eight species (Mugil cephalus, Gerres oblongus, Siganus fuscescens, Terapon jarbua, Sillago maculata, Upeneus tragula, Lutjanus russellii, and Monacanthus chinensis) was detected, with a clear ontogenetic shift in habitat use from mangrove or seagrass beds to coral reefs. The similarity indices suggested that fish assemblages can be divided into three large groups namely coral, seagrass, and mangrove habitat types. This study demonstrated that connectivity exists between mangrove-seagrass-coral reef continuum in Wenchang area; therefore, we recommend that fish connectivity should be considered when designing MPAs or MPA network where possible.
... Oil and gas infrastructure likely increases, or at least focuses, fish production (Claisse et al., 2014), surrounding benthic biomass, diversity, and connectivity (Macreadie et al., 2011) so their removal may reduce secondary production (Pondella et al., 2015). The particular assemblages supported by these structures varies with structure age, water depth and height on the structure and on different timescales (Fujii, 2015;Bond et al., 2018) so there is potentially variation within and between different basins. It is therefore important to develop a better understanding of faunal assemblages supported by offshore infrastructures in order to understand the effect of their removal. ...
Decommissioning of oil and gas infrastructure globally has focused attention on its importance as hard substratum on continental shelf and slope habitats. Observational studies are needed to improve understanding of faunal assemblages supported by offshore infrastructure and better predict the effect of removal. Here, we present results from visual inspection and physical sampling of a small oil and gas industry structure decommissioned from an oil field in the North East Atlantic. This is supported by observations of similar structures nearby and by photographs of the surrounding seabed from environmental baseline surveys. The structure supported a reasonably high biomass and diversity of invertebrates (>10 kg and >39 macrofaunal and 17 megafaunal species) and fishes (>20 kg biomass and >4 species). The invertebrate megafaunal species present on the structure were a sub-set of the hard substratum fauna observed on surrounding seabed. Porifera were absent from the structure. Biological succession in the first 2 years occurred as follows. Sparse colonies of the hydroid Obelia sp. stet were early colonisers then subsequent development of thick hydroid turf (Obelia sp. stet. and Halecium sp. stet.) supported an invertebrate assemblage (2654 individuals kg wet mass–1) dominated by saddle oysters [Pododesmus squama (Gmelin, 1791) and Heteranomia sp. stet.)] and scale worms (Harmothoe spp.). Percentage cover of hydroid turf varied significantly over the structure, with most growth on sections exposed to strongest currents. Commercially important fish species present around the structure included Gadus morhua (Atlantic cod), Pollachius virens (saithe) and Lophius piscatorius (monkfish). Studies of artificial structures such as this provide much needed data to understand their role in the ecology of seafloor habitats and inform environmental decision making on all stages of industry from exploration to decommissioning. We show that the ecological role of the decommissioned three-dimensional structures was to enhance the biomass of a sub-set of epifaunal invertebrates found in the area. This supported diverse associated macrofaunal organisms, providing a food source for motile invertebrates and fishes in an area where background hard substratum can be lost through the impacts of drilling.
... The approach constructs all possible combinations of models and excludes models with collinear variables specified by a Pearson's correlation [ 0.28 (Graham 2003). This technique has great utility for ecological applications exploring the influence of environmental factors on the distribution of biota (Bond et al. 2018;Wellington et al. 2018). ...
Context
Whilst the composition and arrangement of habitats within landscape mosaics are known to be important determinants of biodiversity patterns, the influence of seascape patterning and connectivity on temperate reef fish assemblages remains largely unknown.
Objectives
We examined how habitat patterns at multiple spatial scales (100–1000 m) explained the abundance and diversity of temperate reef fish in a reef-seagrass dominated seascape.
Methods
Fish assemblages were surveyed using remote underwater videos deployed on 22 reefs in Jervis Bay, NSW, Australia. Using full-subset GAMMs, we investigated if habitat area, edge, structural connectivity and a metric for habitat diversity (Shannon’s diversity index) of reef and seagrass can predict variations in a temperate reef fish assemblage.
Results
A key finding of the study was that temperate reefs close (< 55 m) to large (> 6.25 ha) seagrass meadows contained greater abundance and diversity of fish. A consistent negative correlation was also found between reef area (> 0.01 ha) and the fish assemblage. The influence of seascape metrics on the abundance of fishes varied with functional traits (trophic groups, mobility and habitat associations). Fish-seascape relationships occurred at a range of spatial scales with no single scale being solely important for structuring the fish assemblage.
Conclusions
We demonstrate that it is important not to view reef habitats in isolation, rather consider a reefs context to adjacent seagrass when predicting the distribution of temperate reef fish. This finding improves current understanding of the multi-scale factors structuring temperate reef fish assemblages and highlights the importance of reef-seagrass connectivty for the management of temperate marine ecosystems.
... There are numerous examples of other successful shortterm collaborations investigating a range of key questions, including: extent of anthropogenic impacts (Netto et al., 2010); recovery from anthropogenic impacts (Jones et al., 2012), role of infrastructure (Bond et al., 2018); potential impacts on reef-forming corals (Purser, 2015), and characterization of local biodiversity . In the deep-ocean observing context, long-term collaborations are a key focus for further expansion of these synergies. ...
The deep ocean below 200 m water depth is the least observed, but largest habitat on our planet by volume and area. Over 150 years of exploration has revealed that this dynamic system provides critical climate regulation, houses a wealth of energy, mineral, and biological resources, and represents a vast repository of biological diversity. A long history of deep-ocean exploration and observation led to the initial concept for the Deep-Ocean Observing Strategy (DOOS), under the auspices of the Global Ocean Observing System (GOOS). Here we discuss the scientific need for globally integrated deep-ocean observing, its status, and the key scientific questions and societal mandates driving observing requirements over the next decade. We consider the Essential Ocean Variables (EOVs) needed to address deep-ocean challenges within the physical, biogeochemical, and biological/ecosystem sciences according to the Framework for Ocean Observing (FOO), and map these onto scientific questions. Opportunities for new and expanded synergies among deep-ocean stakeholders are discussed, including academic-industry partnerships with the oil and gas, mining, cable and fishing industries, the ocean exploration and mapping community, and biodiversity conservation initiatives. Future deep-ocean observing will benefit from the greater integration across traditional disciplines and sectors, achieved through demonstration projects and facilitated reuse and repurposing of existing deep-sea data efforts. We highlight examples of existing and emerging deep-sea methods and technologies, noting key challenges associated with data volume, preservation, standardization, and accessibility. Emerging technologies relevant to deep-ocean sustainability and the blue economy include novel genomics approaches, imaging technologies, and ultra-deep hydrographic measurements. Capacity building will be necessary to integrate capabilities into programs and projects at a global scale. Progress can be facilitated by Open Science and Findable, Accessible, Interoperable, Reusable (FAIR) data principles and converge on agreed to data standards, practices, vocabularies, and registries. We envision expansion of the deep-ocean observing community to embrace the participation of academia, industry, NGOs, national governments, international governmental organizations, and the public at large in order to unlock critical knowledge contained in the deep ocean over coming decades, and to realize the mutual benefits of thoughtful deep-ocean observing for all elements of a sustainable ocean.
... This is due to the strong dependency of sessile organisms on suitable anchor points. Various consolidated objects, both natural and artificial (e.g., stones, mussel accumulations, shipwrecks, pipelines or construction basements), can provide shelter and substrate for a variety of sessile and mobile species (e.g., [6][7][8]). The sediment composition of the seafloor has a strong influence on the availability of such substrates. ...
Stony grounds form important habitats in the marine environment, especially for sessile benthic organisms. For the purpose of habitat demarcation and monitoring, knowledge of the position and abundance of individual stones is necessary. This is especially the case in areas with a scattered occurrence of stones in an environment which is otherwise characterized by relatively mobile sandy sediments. Exposed stones can be detected using side-scan sonar (SSS) data. However, apart from laborious manual identification, there is as yet no automated or semi-automated method available for a fast and spatially resolved detection of stones. In this study, a Haar-like feature detector was trained to identify individual stones on an SSS mosaic (~12 km2) showing heterogeneous sediment distribution. The results of this method were compared with those of manually derived stones. Our study shows that the Haar-like feature detector was able to detect up to 62% of the overall occurrence of stones within the study area. Even though the sheer number of correctly identified stones was influenced by, e.g., the type of sediments and the number of grey values of the mosaic, Haar-like feature detectors provide a relatively easy and fast method to identify stones on SSS mosaics when compared to the manual investigation.
Knowledge of platform ecology is necessary to best inform decommissioning practice. Remotely operated vehicle (ROV) video is often collected during standard industry operations and may provide insight into the marine life associating with offshore platforms, however, the utility of this video for ecological assessments remains unclear. Archival ROV video surveys at the Wandoo oil platforms on Australia’s North West Shelf was evaluated for its utility, with only 4.9% of imagery usable for standardised ecological studies. Based on the subset of usable ROV video, the influence of depth and structural complexity on attributes of the fish assemblage on the Wandoo oil platforms was examined. Vertical ROV transects on three vertical shafts on the Wandoo platforms were stratified into 10 m depth strata from 0 to 50 m, with 111 fish taxa from 25 families identified and counted across all depth strata. At both platforms, taxonomic richness and abundance was significantly highest in shallow regions and declined with depth. Small reef fish were predominantly associated with structurally complex habitat in shallow regions (<22 m), whilst large demersal species dominated below 32 m. Future decommissioning policy in Australia should consider the vertical fish distributions and the importance of shallow sections of platforms. Finally, the dearth of usable video was due to the haphazard method of collection and it is recommended that future surveys should be conducted according to scientific standards to ensure greater utility of the video for both industry use and scientific research.
Globally, aging offshore oil and gas (O&G) platforms face resource depletion, and regulations often demand platform removal through decommissioning. In the North Sea, >€90 billion will be needed for decommissioning by 2060. However, the influence of O&G platforms on fish communities is poorly understood. This challenges predictions of possible fisheries scenarios associated with different decommissioning options. Here, we examined the role that North Sea platforms played on fish communities. We explored patterns of fish abundance and body size variation along transects from O&G platforms comparing catch per unit effort data. Fish abundance was positively associated with O&G platforms. Atlantic cod, plaice, saithe, and mackerel were most abundant near platforms. Similarly, larger Atlantic cod were near the O&G platforms. Our study provided information for decision‐making regarding platform decommissioning scenarios by evidencing O&G platform habitat provisioning for various commercial fish species.
As the offshore hydrocarbon industry matures and decommissioning activities are expected to increase, there is a requirement to assess the environmental consequences of different pipeline decommissioning options. Previous research on fish and other ecological components associated with pipelines has focused on examining species richness, abundance and biomass surrounding structures. The extent to which subsea pipelines mimic or alter ecosystem function compared with nearby natural habitats is unknown. We analyse differences in fish assemblage biological trait composition and the functional diversity at exposed shallow-water subsea pipelines, nearby natural reef and soft sediment habitats, using mini stereo-video remotely operated vehicles (ROV). Habitats significantly differed in assemblage trait composition. The pipeline and reef habitats shared a more similar functional composition and had the presence of key functional groups required for the development and maintenance of healthy coral reef systems. The reef habitat had the greatest functional diversity, followed by the pipeline habitat and soft sediment habitat respectively.
Introduction
Offshore oil and gas (O & G) infrastructure provides hard substrata of structural complexity in marine environments and has been shown to have ecological value, particularly in oligotrophic environments. As infrastructure approaches end of life, understanding such values is critical to inform decommissioning decisions.
Methods
This study uses a decade of industry remotely operated vehicle (ROV) imagery to describe fish, invertebrate, and benthic communities on gas field infrastructure. Sampling was conducted over 22 km of flowline, three wells and one manifold in the temperate waters of Bass Strait, south east Australia in depths of 155 to 263 m.
Results
A total of 10,343 mobile animals from 69 taxa were observed. A higher diversity of fishes were observed on flowlines (28 taxa) compared to wells (19 taxa). Fish and invertebrate communities observed along flowlines were distinct from those observed on wells/manifold, however, there was also high spatial variability among the different flowlines surveyed and between the three wells and manifold. These differences appear to be driven by habitat and depth preferences of the species observed. Many sand-affiliated species were associated with buried sections of flowlines (Tasmanian giant crab Pseudocarcinus gigas, Balmain bug Ibacus peronii, slender sand burrower Creedia haswelli, red cod Pseudophycis spp., blue grenadier Macruronus novaezelandiae) whilst reef-associated and schooling species were observed on the wells/manifold (jackass morwong Nemadactylus macropterus, redbait Emmelichthys nitidus, splendid perch Callanthias australis). Species of ecological importance were also noted including the Australian fur seal (Arctocephalus pusillus doriferus), long-lived foxfish (Bodianus frenchii), and handfish (Brachionichthyidae spp).
Discussion
This study describes the habitat value of oil and gas infrastructure in a data poor temperate region that is important for understanding how the decommissioning of these structures may affect local marine ecosystems and fisheries. Therefore, it is critical to understand the habitat value of O&G infrastructure to marine life in the Bass Strait and whether decommissioning of these structures affect local marine ecosystems and fisheries. This study shows the complexity of determining temporal change in biodiversity values associated with these O & G structures from historical industry datasets that will be key for informing future decommissioning options. We also provide some guidance on how future quantitative data can be obtained in a systematic way using industry ROV data to better inform ecological investigations and decommissioning options.
The Gippsland Basin is the location of Australia’s oldest offshore oil and gas (O&G) structures, with hydrocarbon production beginning in the 1960s. The Bass Strait flows over this area with fisheries providing seafood for the major population centers of Melbourne, Sydney and beyond. Since Australia’s maritime legislation restricts activities to outside of 500 meters from O&G structures as a security exclusion zone, these O&G structures may serve as de facto marine protected areas that may have spillover effects to local fisheries. Therefore, it is critical to understand the habitat value of O&G infrastructure to marine life in the Bass Strait and whether decommissioning of these structures affect local marine ecosystems and fisheries. We analyzed industry-collected remotely operated vehicle (ROV) imagery from 2008-2018 and compared this data with reported catch data from fishing vessels operating in this region collected by the Australian Fisheries Management Authority (AFMA) from 2008-2018. We assessed species richness and relative abundance on two platforms and two pipelines and compared the species composition with retained catch reported by commercial fishers operating in Commonwealth fisheries. We found diverse communities of fishes and invertebrates around O&G structures, with a different subset of species inhabiting pipelines than platforms. We found little overlap between the species that were targeted by commercial fishers and those found around O&G structures (10% overlap), however, species composition data from fisheries often groups species making the data coarse and under-representative of true species diversity. Fishery-independent data from ROV imagery or other methods greatly augments our understanding of deepwater marine communities, including those around O&G structures. Combining data sources provides a holistic look at these novel ecosystems and provides better insight into future decommissioning scenarios.
Offshore oil and gas platforms have a finite life of production operations. Once production ceases, decommissioning options for the platform are evaluated. The role that a platform's jacket plays as invertebrate habitat can inform the decommissioning decision. Worldwide, very few scientific surveys of marine invertebrates have been conducted at platforms to collect data needed for biological assessments; however, recent research has used archived video from routine industry inspections of platform jackets to examine the biological community. To address concerns of bias in using industry structural integrity surveys for biological assessments, we compared estimates of invertebrate abundance and diversity beneath a California oil platform determined using data from three sources: video from an industry remote operated vehicle (ROV) “structural” survey, video from a scientific ROV “biological” survey using the same vehicle, and photoquadrat still imagery from a scientific scuba diver survey. All surveys were conducted along the same jacket crossbeams. We found that the invertebrate species assemblages characterized by the two ROV methods were similar; more species were observed in the diver photoquadrats than in either of the two kinds of ROV surveys, because smaller and more cryptic species could be resolved. While we cannot extrapolate from this study to all platforms worldwide, routine platform structural integrity surveys are a valuable source for opportunistic marine community surveys. Intentional planning of the structural survey to incorporate minor adjustments (e.g., maintaining fixed ROV distance from the infrastructure at a slower speed and consistent camera angle) coupled with a deliberate consideration of the platform ecology (e.g., spatial variability in community composition on the platform jacket) can substantially improve the effects on invertebrate assemblage assessments from routine surveys.
Subsea pipelines and wells installed to support the oil and gas industry represent some of the most extensive and numerous anthropogenic structures throughout global marine ecosystems. There remains a paucity of information on the habitat value of these structures for fishery target species and, as a result, little understanding of how decommissioning should be conducted to minimise impacts to populations of these economically and socially important species. We assess the diversity and abundance of species that are targets of recreational and commercial fisheries on 33 subsea wells and 17 pipelines across the tropical northwest and temperate southeast marine regions of Australia. We examine relationships between fish identity and abundance and a range of environmental (e.g., depth, location), infrastructure-specific (e.g., pipeline position, diameter, age, length of pipeline, height of well, position on well), and biological (% cover of epibiota) variables using video filmed by remotely operated vehicles during their routine offshore inspection and maintenance campaigns. A total of 100 fishery target species were observed across subsea well and pipeline infrastructure, 56 species uniquely observed on pipelines and nine unique to wells. The families Lutjanidae (snapper), Serranidae (rock cods, groupers, perch), and Carangidae (trevallies) were most common and abundant on both wells and pipelines. In the northwest, lutjanids were most abundant around the base of wells, in shallow depths, on shorter wells, and where pipelines spanned the seafloor. A greater number of fishery target species and abundance of ocean perch (Helicolenus spp.) were also associated with pipelines that spanned the seafloor in temperate southeast Australia. The combined biomass of three species of snapper on wells in the northwest was 1,270 kg, with production levels for these species on each well estimated to be 105.2 g m² year⁻¹. The present study serves as an important reference point for informing decommissioning decisions for pipeline and well infrastructure and demonstrates the utility of industry-held data for science. We suggest that key predictor variables identified here be incorporated into comprehensive before-after-control-impact scientific studies for specific fields/assets to enable the prediction of potential impacts of decommissioning scenarios on marine communities present and quantification of such impacts after the decommissioning activity has occurred.
In recent times, decommissioning of offshore platforms has become an even more discussed topic, for its relevant environmental, social, and economic repercussions. In particular, by carrying out economic considerations, all the divestiture possibilities applicable to an offshore platform and the relative sustainable business models (SBMs) will be analyzed in a wide framework of the circular economy and sustainable principles. In this scenario, sustainable decommissioning (SD) of offshore platforms process refers to multidimensional and interdisciplinary challenges, which requires a deep understanding of technical, legal, economic, financial, social, and environmental variables. The decommissioning of these structures is an issue that has gained a great deal of international attention and will require in the next years an open dialogue and exchange between institutions, oil and gas companies, enterprises, and the environment.
Offshore platforms, subsea pipelines, wells and related fixed structures supporting the oil and gas (O&G) industry are prevalent in oceans across the globe, with many approaching the end of their operational life and requiring decommissioning. Although structures can possess high ecological diversity and productivity, information on how they interact with broader ecological processes remains unclear. Here, we review the current state of knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological connectivity with natural marine habitats. There is a paucity of studies on the subject with only 33 papers specifically targeting connectivity and O&G structures, although other studies provide important related information. Evidence for O&G structures facilitating vertical and horizontal seascape connectivity exists for larvae and mobile adult invertebrates, fish and megafauna; including threatened and commercially important species. The degree to which these structures represent a beneficial or detrimental net impact remains unclear, is complex and ultimately needs more research to determine the extent to which natural connectivity networks are conserved, enhanced or disrupted. We discuss the potential impacts of different decommissioning approaches on seascape connectivity and identify, through expert elicitation, critical knowledge gaps that, if addressed, may further inform decision making for the life cycle of O&G infrastructure, with relevance for other industries (e.g. renewables). The most highly ranked critical knowledge gap was a need to understand how O&G structures modify and influence the movement patterns of mobile species and dispersal stages of sessile marine species. Understanding how different decommissioning options affect species survival and movement was also highly ranked, as was understanding the extent to which O&G structures contribute to extending species distributions by providing rest stops, foraging habitat, and stepping stones. These questions could be addressed with further dedicated studies of animal movement in relation to structures using telemetry, molecular techniques and movement models. Our review and these priority questions provide a roadmap for advancing research needed to support evidence‐based decision making for decommissioning O&G infrastructure. Offshore platforms and related fixed structures supporting the oil and gas (O&G) industry are prevalent in all oceans. We review current knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological seascape connectivity. There is a paucity of studies assessing connectivity and O&G structures. We discuss existing knowledge and identify critical knowledge gaps for decision‐making, such as the need to understand how O&G structures modify and influence movement patterns of mobile species and dispersal. Our review and priority questions provide a roadmap for advancing research needed to support evidence‐based decision‐making for decommissioning O&G infrastructure.
The decommissioning of offshore oil and gas platforms typically involves removing some or all of the associated infrastructure and the consequent destruction of the associated marine ecosystem that has developed over decades. There is increasing evidence of the important ecological role played by offshore platforms. Concepts such as novel ecosystems allow stakeholders to consider the ecological role played by each platform in the decommissioning process. This study focused on the Wandoo field in Northwest Australia as a case study for the application of the novel ecosystem concept to the decommissioning of offshore platforms. Stereo-baited remote underwater video systems were used to assess the habitat composition and fish communities at Wandoo, as well as two control sites: a sandy one that resembled the Wandoo site pre-installation, and one characterized by a natural reef as a control for natural hard substrate and vertical relief. We found denser macrobenthos habitat at the Wandoo site than at either of the control sites, which we attributed to the exclusion of seabed trawling around the Wandoo infrastructure. We also found that the demersal and pelagic taxonomic assemblages at Wandoo more closely resemble those at a natural reef than those which would likely have been present pre-installation, but these assemblages are still unique in a regional context. The demersal assemblage is characterized by reef-associated species with higher diversity than those at the sand control and natural reef control sites, with the pelagic community characterized by species associated with oil platforms in other regions. These findings suggest that a novel ecosystem has emerged in the Wandoo field. It is likely that many of the novel qualities of this ecosystem would be lost under decommissioning scenarios that involve partial or complete removal. This study provides an example for classifying offshore platforms as novel ecosystems.
Coral reef ecosystems are under increasing anthropogenic pressures making it ever more important to monitor changes in fish communities to implement appropriate management. In contrast to long-term spatial and temporal variation which has been extensively documented, little work has been carried out to identify variability in fish assemblages on short time scales, with few studies testing patterns of fish assemblages between and within days. Here we investigated the diurnal changes in species richness, relative abundance and assemblage composition in a shallow coral reef fish community in Egypt. To do so, a section of coral reef was filmed during the morning (0600 h), midday (1000 and 1400 h) and afternoon (1800 h) over eleven days. Dusk (0600 h) and dawn samples (1800 h) showed higher species richness compared to late morning (1000 h) and mid-day samples (1400 h) and borderline significantly higher numbers of total individuals, likely associated with feeding activity and predator avoidance. Assemblage composition varied across days and time-of-day, showing greater variability during dusk and dawn associated with a transition between day-time and night-time assemblages. Our results have implications for designing coral reef fish surveys, emphasising that short-term changes in fish communities should be considered when designing experiments to monitor fish assemblages over time. Where possible, we suggest increasing replication within sites and time scales or randomising data within a specific time window at all sites, looking to exclude dusk and dawn.
In recent years, video footage obtained from routine industry surveys using remotely operated vehicles (ROVs) has been used to assess fish assemblages associated with offshore oil and gas infrastructure. However, as industry moves towards using autonomous underwater vehicles (AUVs), it is important to understand how such a change may affect assessments of fish assemblages and whether these data collected from AUVs can be directly compared to those collected from historic and future ROV footage. In an extremely rare opportunity, we compare fish assemblages surveyed by an industrial ROV and an industrial hybrid-AUV (H-AUV) along the same 2,060-m section of subsea pipeline, at the same time of day, within 1 day of each other. A total of 206 transects, each 20 m in length, were analyzed, recording 406 fish from 10 species. The H-AUV recorded all 10 fish species, while the ROV recorded seven. Mean species richness was ~4% higher for H-AUV, and mean abundance was ~21% higher for ROV; these differences can be considered negligible. Multivariate analysis revealed nonsignificant differences in species composition between survey methods. This result suggests that future surveys of fish at this pipeline using a similar H-AUV can yield comparable results to ROV and, as such, facilitate comparison to historical ROV imagery. Future surveys of pipelines with AUV should consider adding extra lighting and high-definition cameras onto booms similar to those operating on ROVs, which will provide a useful field of view into pipeline spans and make it easier to identify fish. Our study provides insight into the utility and comparability of industry ROV and AUV pipeline inspection footage for the assessment of fish assemblages associated with subsea pipelines, which is used to inform policies and practices on the installation and decommissioning of subsea infrastructure.
Subsea pipelines have been installed in all major hydrocarbon basins across the globe to support the offshore Oil & Gas (O&G) industry. These artificial structures provide hard substratum that can be colonised and utilised by sessile and mobile organisms. The present study utilises industry-collected remotely operated vehicle (ROV) video to assess fish species richness and abundance, and marine growth type, extent and complexity along sections of a subsea gas pipeline, in 56-82 m depth, that traverses the Australian Commonwealth Montebello Marine Park (MMP). A total of 7493 fish from 81 species and 33 families were recorded from 606 analysed 10 m transects spaced across sections of the pipeline. Of these 81 species, 27 are considered fishery-target species in the Pilbara Demersal Scalefish fishery (PDSF), with select commercial fishing activities permitted with authorisation within the Marine Park. A moderate abundance (175) of sub-adult red emperor (Lutjanus sebae), a fishery-indicator species, were observed along the pipeline. Eleven different categories of marine growth habitat were observed, with the pipeline possessing quite uniform coverage of encrusting marine growth (coralline algae, bryozoans, ascidians, etc.) with patchy occurrences of more structurally complex sponges and black/octocoral forms. Fish species richness and abundance of the commercially targeted Moses' snapper (Lutjanus russellii) were correlated positively with increasing cover of sponges. The pipeline itself had very few spans and was never more than fractionally buried. Despite the somewhat homogenous habitats, depths, and position of the pipeline relative to the seafloor, presence of a field joint indent had a positive influence on the abundance of some common and commercially important fish species. This study demonstrates the ecological value of ROV footage obtained during industry inspection operations that were conducted for reasons unrelated to the determination of ecological information. The pipeline offers a corridor of hard bottom habitat within a marine park that facilitates epibiotic growth and the presence of reef-associated species in a region characterised by sandy sediments. Results indicate the potential importance of subsea O&G infrastructure as a habitat for fish, and in consequence, potentially also as structures with value to fisheries.
Oil and gas pipelines that lie exposed on the seabed can function as “artificial reefs,” providing habitat for fish and benthic species, including some that are listed under conservation designations. As the offshore hydrocarbon industry matures, operators and national governments must decide whether decommissioned pipelines should be left in situ or removed for onshore disposal. In most jurisdictions, there is a requirement to evaluate the environmental consequences of different pipeline decommissioning options in a comparative assessment. To do this effectively requires an understanding of the associations between pipelines and fauna. Pipeline operators routinely collect video footage for inspection and maintenance purposes using remotely operated vehicles (ROV). This footage has the potential to provide insight into interactions between the marine environment and offshore pipelines. This study uses inspection footage from eight pipelines to quantify the presence and abundance of species and features listed under a number of EU and United Kingdom conservation designations; 12 such features and species were observed on the pipelines or neighboring sediments. The soft coral Alcyonium digitatum was present in the highest densities on pipelines located on mud, while Sabellaria sp. and Echinus esculentus were more common on pipelines in sand. Gadoids, anemones and hermit crabs were also frequently observed around pipelines. The study identifies the limitations to the use of industry ROV footage for ecological purposes, but shows that with consideration of taxon size, image resolution, ROV speed and altitude, this can be a valuable approach to gain additional insights into environment-infrastructure interactions. The results suggest that removal of pipelines will remove established colonies of epibenthic species, some of which have conservation value. The ecological significance of this loss, however, must be weighed against the broader considerations during pipeline decommissioning including cost, technical feasibility and impacts to other marine users.
This paper describes the potential global scientific value of video and other data collected by Remotely Operated Vehicles (ROVs). ROVs are used worldwide, primarily by the offshore oil and gas industry, to monitor the integrity of subsea infrastructure and, in doing so, collect terabytes of video and in situ physical data from inaccessible regions and poorly understood marine environments. The paper begins by describing how recent ROV surveys for projects in Australia have gained a new dimension by involving marine scientists in their interpretation. A previously unrecognised influence of marine life on oil and gas pipelines was uncovered, triggering new collaborations between industry and marine science.
This new collaboration prompted a team of international engineers and marine scientists to gather together with West Australian based members of the oil and gas sector and ROV operators, to examine the global scientific value of ROV-collected data. If made available for research, these data have immense value for science to quantify the marine ecology and assist good stewardship of this environment by industry. It was found that most ROV operations are conducted by industry in a way that fulfils immediate industry requirements but which can confound scientific interpretation of the data. For example, there is variation in video resolution, ROV speed, distance above substrate and time (e.g. both seasonal and time of day), and these variations can limit the quantitative conclusions that can be drawn about marine ecology. We examined potential cost-effective, simple enhancements to standard ROV hardware and operational procedures that will increase the value of future industrial ROV operational data, without disrupting the primary focus of these operations.
The ecological value of existing ROV data represents an immense and under-utilized resource with worldwide coverage. We describe how ROVs can unravel the mysteries of our oceans, yield scientific discoveries, and provide examples of how these data can allow quantification of the ecological value of subsea infrastructure. By using these data, we can greatly improve our knowledge of marine biodiversity on and around offshore infrastructure and their environmental impact on marine ecosystems, both of which are particularly important in the consideration and selection of decommissioning strategies. Predicting the environmental consequences of removing or retaining subsea structures after decommissioning relies on an understanding of the ecological communities that have developed in association with these structures during their operational lives. Making industrial ROV data available for scientific research, and collating it in the future using modified protocols, would provide a very positive contribution to both science and industry, allowing the environmental impacts of subsea infrastructure to be quantified. It will also allow industry to contribute to a broader scientific understanding of our oceans, given the location of ROVs in areas that can rarely be accessed by independent researchers. This would provide novel and valuable information about under-researched and little known regions of the world's oceans.<br/
Full-subsets information theoretic approaches are becoming an increasingly popular
tool for exploring predictive power and variable importance where a wide range of
candidate predictors are being considered. Here, we describe a simple function in the
statistical programming language R that can be used to construct, fit, and compare a
complete model set of possible ecological or environmental predictors, given a re-
sponse variable of interest and a starting generalized additive (mixed) model fit. Main advantages include not requiring a complete model to be fit as the starting point for
candidate model set construction (meaning that a greater number of predictors can
potentially be explored than might be available through functions such as dredge);
model sets that include interactions between factors and continuous nonlinear pre-
dictors; and automatic removal of models with correlated predictors (based on a user
defined criterion for exclusion). The function takes continuous predictors, which are
fitted using smoothers via either gam, gamm (mgcv) or gamm4, as well as factor vari-
ables which are included on their own or as two- level interaction terms within the
gam smooth (via use of the “by” argument), or with themselves. The function allows
any model to be constructed and used as a null model, and takes a range of arguments
that allow control over the model set being constructed, including specifying cyclic
and linear continuous predictors, specification of the smoothing algorithm used, and
the maximum complexity allowed for smooth terms. The use of the function is dem-
onstrated via case studies that highlight how appropriate model sets can be easily
constructed and the broader utility of the approach for exploratory ecology.
Imagery collected by still and video cameras is an increasingly important tool for minimal impact, repeatable observations in the marine environment. Data generated from imagery includes identification, annotation and quantification of biological subjects and environmental features within an image. To be long-lived and useful beyond their project-specific initial purpose, and to maximize their utility across studies and disciplines, marine imagery data should use a standardised vocabulary of defined terms. This would enable the compilation of regional, national and/or global data sets from multiple sources, contributing to broad-scale management studies and development of automated annotation algorithms. The classification scheme developed under the Collaborative and Automated Tools for Analysis of Marine Imagery (CATAMI) project provides such a vocabulary. The CATAMI classification scheme introduces Australian-wide acknowledged, standardised terminology for annotating benthic substrates and biota in marine imagery. It combines coarse-level taxonomy and morphology, and is a flexible, hierarchical classification that bridges the gap between habitat/biotope characterisation and taxonomy, acknowledging limitations when describing biological taxa through imagery. It is fully described, documented, and maintained through curated online databases, and can be applied across benthic image collection methods, annotation platforms and scoring methods. Following release in 2013, the CATAMI classification scheme was taken up by a wide variety of users, including government, academia and industry. This rapid acceptance highlights the scheme's utility and the potential to facilitate broad-scale multidisciplinary studies of marine ecosystems when applied globally. Here we present the CATAMI classification scheme, describe its conception and features, and discuss its utility and the opportunities as well as challenges arising from its use.
Animal-derived nutrients play an important role in structuring nutrient regimes within and between ecosystems. When animals undergo repetitive, aggregating behavior through time, they can create nutrient hotspots where rates of biogeochemical activity are higher than those found in the surrounding environment. In turn, these hotspots can influence ecosystem processes and community structure. We examined the potential for reef fishes from the family Haemulidae (grunts) to create nutrient hotspots and the potential impact of these hotspots on reef communities. To do so, we tracked the schooling locations of diurnally migrating grunts, which shelter at reef sites during the day but forage off reef each night, and measured the impact of these fish schools on benthic communities. We found that grunt schools showed a high degree of site fidelity, repeatedly returning to the same coral heads. These aggregations created nutrient hotspots around coral heads where nitrogen and phosphorus delivery was roughly 10 and 7 times the respective rates of delivery to structurally similar sites that lacked schools of these fishes. In turn, grazing rates of herbivorous fishes at grunt-derived hotspots were approximately 3 times those of sites where grunts were rare. These differences in nutrient delivery and grazing led to distinct benthic communities with higher cover of crustose coralline algae and less total algal abundance at grunt aggregation sites. Importantly, coral growth was roughly 1.5 times greater at grunt hotspots, likely due to the important nutrient subsidy. Our results suggest that schooling reef fish and their nutrient subsidies play an important role in mediating community structure on coral reefs and that overfishing may have important negative consequences on ecosystem functions. As such, management strategies must consider mesopredatory fishes in addition to current protection often offered to herbivores and top-tier predators. Furthermore, our results suggest that restoration strategies may benefit from focusing on providing structure for aggregating fishes on reefs with low topographic complexity or focusing the restoration of nursery raised corals around existing nutrient hotspots.
Should we "reef" obsolete oil platforms? Claisse et al. (1) show that not only do oil platforms produce fish, but they do so at a rate far greater than our most productive marine habitats, such as coral reefs and mangroves. Because this information may be used to jus-tify increased "reefing" of obsolete oil infra-structure worldwide, we offer some caveats. Although Claisse et al.'s (1) production estimates further our understanding of the habitat value of oil platforms, they bring us little closer to deciding the fate of these struc-tures worldwide. It has been known for more than a decade that platforms are capable of providing valuable habitat for fish, yet habitat value appears to vary greatly among plat-forms, even among those located in similar ecological settings (2). This conclusion is sup-ported by the total production values in fig-ure 3 of Claisse et al. (1), with some platforms off California producing nearly nine times more fish biomass than others. Productivity data for one platform therefore cannot be used to infer the productivity of other plat-forms. Crucially, this means that the produc-tivity values obtained by Claisse et al. (1) should not be used to inform "rigs-to-reefs" decisions for the remaining 11 platforms off California, nor should they be used to inform rigs-to-reefs policies in other regions of the world. Given that even the least productive platform off California was more productive than surrounding natural reefs (1), why not just convert all platforms into artificial reefs? Because habitat value is only one of many factors that must be considered when making rigs-to-reefs decisions. Other factors include biodiversity value besides fish, po-tential contamination, and impacts on soft-bottom communities, as well as stakeholder impacts (e.g., loss of trawling grounds) and financial costs (including those to the tax-payer) (3). These factors and many others must be weighed against each other to deter-mine the net best decommissioning solution, which may not be a rigs-to-reefs conversion if the habitat benefits are outweighed by other negative impacts (4). We argue that a holistic approach should be taken to decommissioning decisions for oil platforms. Research to date has been overly focused on a small number of factors relating to the decision, such as fish production. More effort is required to identify the full range of factors that need to be considered and to integrate these into the decision process. Formal decision frameworks will be essential in this regard. Multicriteria decision frame-works are capable of handling the complex tradeoffs generated by multiple competing factors and have already been used for decades to solve similar decision problems in the fields of forestry and waste manage-ment (5). These frameworks also reduce bias and increase transparency of the decision process, which is particularly important for offshore decommissioning decisions due to the involvement of strongly conflicting stake-holder groups (e.g., commercial fishers and recreational anglers) (2, 4). If a holistic approach is not adopted, decommissioning options for platforms will likely remain highly regulated, and rigs-to-reefs will be viewed as little more than a controversial cost-saving stunt by the oil and gas industry.
Little is known regarding bias attributable to fish behavior for visual transects conducted using underwater vehicles (UVs). Experiments were conducted under 2 ambient illuminations to assess the behavioral responses of 7 north Pacific Ocean groundfish species to a light stimulus that simulated the approach of a UV. Species included sablefish Anoplopoma fimbria, Pacific halibut Hippoglossus stenolepis, lingcod Ophiodon elongatus and 4 species in the genus Sebastes: blue rockfish S. mystinus, black rockfish S. melanops, copper rockfish S. caurinus and quillback rockfish S. maliger. Movement, as well as general activity, varied greatly between species. The most active species, sablefish, became agitated and moved away from the looming light source, while the least active species, Pacific halibut and lingcod, typically remained stationary. Of the 4 rockfish species, 2 demonstrated a strong response to ambient light level. Black rockfish and blue rockfish moved away from the looming light source, but avoidance was delayed under high ambient light. Bias probably differs among species, being greatest for those that are highly active and mobile, like sablefish. Further, ambient light may modulate bias, such that researchers need to be cautious about comparing results for surveys conducted at different depths and/or times of day.
Significance
Secondary production is the formation of new animal biomass from growth for all individuals in a given area during some period of time. It can be a powerful tool for evaluating ecosystem function because it incorporates multiple characteristics of a population or community of organisms such as density, body size, growth, and survivorship into a single metric. Here, we find that fish communities living on the complex hardscape habitat created throughout the water column by the structure of oil and gas platforms off California have the highest secondary production per unit area of seafloor of any marine ecosystem for which similar estimates exist.
It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (backscattering) data collection at a seamount to verify if its behaviour is dominated by vertical movements as a response to temporal changes in environmental conditions and pelagic prey availability. We found that seabream extensively migrate up and down the water column, that these patterns are cyclic both in short-term (tidal, diel) as well as long-term (seasonal) scales, and that they partially match the availability of potential DSL prey components. Furthermore, the emerging pattern points to a more complex spatial behaviour than previously anticipated, suggesting a seasonal switch in the diel behaviour mode (benthic vs. pelagic) of seabream, which may reflect an adaptation to differences in prey availability. This study is the first to document the fine scale three-dimensional behaviour of a deep-sea fish residing at seamounts.
Artificial reefs are used by many fisheries managers as a tool to mitigate the impact of fisheries on coastal fish communities by providing new habitat for many exploited fish species. However, the comparison between the behavior of wild fish inhabiting either natural or artificial habitats has received less attention. Thus the spatio-temporal patterns of fish that establish their home range in one habitat or the other and their consequences of intra-population differentiation on life-history remain largely unexplored. We hypothesize that individuals with a preferred habitat (i.e. natural vs. artificial) can behave differently in terms of habitat use, with important consequences on population dynamics (e.g. life-history, mortality, and reproductive success). Therefore, using biotelemetry, 98 white seabream (Diplodus sargus) inhabiting either artificial or natural habitats were tagged and their behavior was monitored for up to eight months. Most white seabreams were highly resident either on natural or artificial reefs, with a preference for the shallow artificial reef subsets. Connectivity between artificial and natural reefs was limited for resident individuals due to great inter-habitat distances. The temporal behavioral patterns of white seabreams differed between artificial and natural reefs. Artificial-reef resident fish had a predominantly nocturnal diel pattern, whereas natural-reef resident fish showed a diurnal diel pattern. Differences in diel behavioral patterns of white seabream inhabiting artificial and natural reefs could be the expression of realized individual specialization resulting from differences in habitat configuration and resource availability between these two habitats. Artificial reefs have the potential to modify not only seascape connectivity but also the individual behavioral patterns of fishes. Future management plans of coastal areas and fisheries resources, including artificial reef implementation, should therefore consider the potential effect of habitat modification on fish behavior, which could have key implications on fish dynamics.
Day-night changes in fish communities were quantified in 6 associated shallow-water biotopes within a single bay: mangroves, seagrass beds, algal beds, channel, fossil reef boulders, and notches in fossil reef rock. All biotopes, except the algal beds, showed a strong reduction in fish density and species richness at night, caused by absence of diurnally active fishes and migrations of Haemulidae and Lutjanidae to the seagrass beds. The fish fauna of the different biotopes showed a relatively high dissimilarity between day and night. This dissimilarity is largely caused by absence of Acanthuridae, Chaetodontidae, Labridae, Pomacentridae, Scaridae and Sparidae at night. These fishes seek shelter at night in, amongst others, the channel, notches and boulders. The balloonfish Diodon holocanthus utilised almost all biotopes as shelter as well as feeding sites. The wide distribution of its preferred food (molluscs) probably explains its distribution in most biotopes at night. The nocturnally active Haemulidae and Lutjanidae, on the other hand, migrated from their daytime shelter sites to the seagrass beds at night to feed. Some of these fishes also migrated to the algal beds to feed. The preference of Haemulidae and Lutjanidae for the seagrass bed as a feeding biotope, instead of other bay biotopes, appears to be related to the relatively high availability of their preferred food (Tanaidacea and Decapoda) as determined by digestive tract analysis. Other bay biotopes showed much lower densities of such food items compared to the seagrass beds.
The pelagic Sargassum community of the western Atlantic Ocean is species rich, with high densities of predatory fishes and invertebrates living in close association with the floating seaweed. Little, however, is known about predator-prey interactions among Sargassum inhabitants and the factors that might help maintain this species richness. To assess how predators may affect the abundance of sessile Sargassum epiphytes, and how these epiphytes may defend themselves against predators, we examined interactions between the most abundant small predator associated with Sargassum mats, the filefish Monacanthus hispidus, and 4 epiphytic hydroid species. This fish was the only Sargassum-associated predator to significantly consume hydroids in initial assays. When filefish were given a simultaneous choice of all 4 hydroid species, they consumed 40 to 45% of 3 species (Clytia noliformis, Aglaophenia latecarinata, and Tridentata turbinata), but consumed less than 5% of the fourth species, Tridentata marginata. Filefish consistently rejected small portions of T. marginata colonies, but consumed a palatable control food. Bioassay-guided fractionation of T. marginata extract resulted in the isolation of a single deterrent secondary metabolite, tridentatol A. Three additional metabolites (tridentatols B to D) had no effect on filefish feeding. In addition to the defensive role of tridentatol A, the tridentatols (A to D) strongly absorb damaging solar ultraviolet (UV) radiation, and thus may function as sunscreens. To our knowledge, this is the first demonstration of chemical defenses among the pelagic Sargassum fauna, and the first report that a hydroid secondary metabolite deters consumers. Prey chemical defenses are an important factor in maintaining species richness in many predator-rich communities, but despite being chemically defended from predators, T. marginata was far less abundant than any of the other, more palatable, hydroids. The factors that allow high-preference hydroids to persist in such a predator-rich community remain unknown.
Fish communities and other ecological variables were sampled for 6 mo (May to October) in successive years (1979, 1980) at vegetated and non-vegetated areas in 2 distinctively different littoral zones (an open bay and a protected cove) of mid-salinity Chesapeake Bay, USA. Fish abundance, biomass and species richness were h~gher in vegetated areas at both sites, and were significantly correlated with macrophyte biomass Diel patterns of fish abundance varied, but highest catches generally occurred at dusk or at night. At one sampling site fish assemblages were dominated by smaller individuals in the vegetated area, suggesting an attraction of juveniles to macrophyte beds for food or refuge from predation. Larger piscivorous fish, which were also caught in greater numbers in vegetated areas, may have been attracted there by higher densities of forage fish. At the cove site the biomass of Paleomonetes sp. was comparable to that of the fish community towards the end of the plant growing season. Benthic infauna were also more abundant in vegetated areas at both sites, and stomach analyses indicated these organisms to be the dominant food resources for common fishes. Diets were generally non-selective in non-vegetated areas while highly selective for epiphytic fauna in macrophyte beds. Fish stomachs were also significantly fuller in vegetated areas, indicating generally greater feeding success. Fish production varied among major species but was higher overall at vegetated areas, following the seasonal patterns of primary production. Most of the differences in fish production between areas were attributable to higher instantaneous growth rates rather than higher biomass. It appears that the greater abundance and species richness of fish assemblages in vegetated areas of this region of Chesapeake Bay resulted from the attractiveness of these habitats as rich sources of preferred foods.
Dynamena crisioides is generally restricted to lower intertidal and shallow subtidal habitats along tropical and subtropical coasts. The hydroid was abundant during this study on prop roots of red mangroves (Rhizophora mangle) at Twin Cays, Belize, where it ranged vertically from 1.1 m below mean tide level (MTL) to 2-3 cm above MTL. The estimated percentage cover of the hydroid was maximal in the lower half of the intertidal zone (MTL and 0.1 m below MTL) and declined rapidly above and below that level. Colony height and number of branches per colony were also consistently highest in hydroids from the lower half of the intertidal zone. The percentage of colonies with gonophores was lowest at the lower and upper vertical limits of the species. Field observations and transplantation experiments suggest that the lower limits of D. crisioides are established by competition for space (with algae, sponges, and ascidians), smothering (by algae, sponges, ascidians, and other hydroids), and predation (by fishes). Desiccation was considered the prime factor determining the upper limits of the hydroid. Colonies transplanted to the supratidal zone were in good condition after 24 h, alive but in poor condition after 48 h, and dead after 72 and 96 h of exposure.
Artificial reefs are used to enhance recreational fishing and diving opportunities in the marine environment. Until recently, demand for artificial reefs in the Great Barrier Reef Marine Park (GBRMP) has been low due to the high value placed on the natural ecosystem of the Great Barrier Reef (GBR) and the abundance of fishing and diving opportunities it provides. In the GBRMP, where there are multiple stakeholder groups with diverse and often conflicting values and opinions, the deployment of artificial reefs will be a complex and controversial social issue. We review the available socio-economic literature regarding the deployment, use, and management of artificial reefs, and aim to identify and understand potential socio-economic issues and information gaps surrounding deployment of artificial reefs in the GBRMP. We also outline a strategy to guide decision-making and maximize the socio-economic value of artificial reefs should they be deployed in the GBRMP.
The feeding mechanism of the euryaline basket star Gorgonocephalus arcticus (Leach) from the Bay of Fundy is described from in situ and laboratory observations of feeding behaviour, analysis of gut contents, and examination of the anatomy and microanatomy of the arms. Gorgonocephalus arcticus, which is abundant in areas of moderate to strong current flow, is a fortuitous predatory suspension feeder, coiling and bending its arms to capture prey. The predominant food item in the gut was the euphausiacean Meganyctiphanes norvegica. Food capture by arm bending and coiling is assisted by the adherence of food to rings of sharp hooks on the arm. The role of the tube feet in food capture appears to be minor. Owing to the form of the feeding fan, the animal is adapted for life in strong currents. There is morphological evidence for the presence of mutable collagenous tissues which may be important in maintaining the feeding fan.
An oil pipeline and its surrounding seafloor, located in the Santa Barbara Channel, southern California, were surveyed for fishes using a manned research submersible. The parts of the pipeline and seafloor surveyed were situated in waters 95235 m deep. Some sections of the surveyed pipe were covered with both sessile and motile invertebrates, such as sea anemones (Metridium cf. farcimen) and sea urchins (Allocentrotus fragilis), sea stars (particularlyHippasteria cf. spinosa andStylasterias cf. forreri ), basket stars (Gorgonocephalus eucnemis ), spot prawns (Pandalus platyceros), and king crabs (Paralithodes californiensis). Based on differences in fish assemblages, four habitats (shallow and deep pipeline and shallow and deep seafloor) were categorized. Fish densities along the shallow portion of the pipeline were about seven times higher than on the adjacent seafloor and densities along the deep pipeline portion were nearly six times that of the deeper seafloor. Along the pipeline, rockfishes comprised 84% of the fishes and included 22 species. Unidentified sanddabs (probably most or all Citharichthys sordidus), forming 33.2%, and combfishes (Zaniolepis frenata and Z. latipinnis), comprising 19% of the total, were most often observed on the seafloor. Most of the fishes living on the pipeline were either juveniles of such larger taxa as blackgill (Sebastes melanostomus), flag (S. rubrivinctus), and vermilion (S. miniatus) rockfishes, cowcod (S. levis), and lingcod (Ophiodon elongatus), or diminutive species such as halfbanded (S. semicinctus) and stripetail (S. saxicola) rockfishes, combfishes (Zaniolepis spp.), and poachers (Family Agonidae). Higher densities of fishes were often noted in areas of the pipeline that had been undercut. Of particular interest were the relatively high densities of juvenile cowcod along the deeper parts of the pipeline, densities that were far higher than any seen at over 80 natural outcrops and at ten platforms. We suggest that, in the process leading to oil platform and pipeline decommissioning, it is important to understand the role that human-made structure plays as fish habitat.
Somatic growth and somatic and gonadal production were estimated during May-November 1989 for six species, comprising most of the standing crop biomass of the fishes on a shallow (10- to 15-m deep), 14-year-old, quarry rock reef (Torrey Pines Artificial Reef 2, TPAR), off La Jolla, California. Observations suggest that the elaboration of tissue unrelated to yield is nontrivial and represents a major component of energy flow through the fishes in this reef system and perhaps others. -from Authors
Rapid colonization, high fish densities, and high catch rates at artificial reefs have been used as evidence for habitat-limitation and increased production of reef fishes. An alternative hypothesis is that artificial reefs attract fishes due to behavioral preferences but do not increase reef fish production or abundance. Reviewed literature reveals that except in one case evidence for increased production is mostly anecdotal and inadequate. Attraction and/or production by a particular artificial reef is predicted to depend on the species and individual ages (size) of reef fish, and on reef location. Factors predicted to be important are natural reef availability, mechanisms of natural population limitation, fishery exploitation pressure, life history dependency on reefs, and species-specific and age-specific behavioral characteristics. Increased production is most likely at locations isolated from natural reefs, and for habitat-limited, demersal, philopatric, territorial, and obligatory reef species. Attraction should be more important in locations with abundant natural reef habitat; where exploitation rates are high; and for recruitment-limited, pelagic, highly mobile, partially reef-dependent, and opportunistic reef species. Artificial reefs are unlikely to benefit heavily exploited or overfished populations without other management actions.
The feeding habits of fish, their production, and their fidelity to the reef habitat were estimated on and near Torrey Pines Artificial Reef (TPAR) during April-October 1989. Taxonomic and biomass analysis of gut contents and benthic resources suggested that at least 70% of the diet of reef fish was derived from the reef itself, and another 20-25% from the ecotone. For most reef fishes, suitable prey was 100 times more abundant in the reef habitat than in adjacent sand habitats. Estimates of somatic production by tagged fish were based on standing stocks, size distribution, and growth rates, and by untagged species, on changes in mean length of a cohort or population biomass over time. Estimated total production of the fish on TPAR was 116 kg, or 649 kg·ha−1, more than a third of it as gonadal production by the six target species. Production by the sand-bottom fish assemblage, estimated from literature-derived somatic and gonadal production rates and the biomass of trawled fish, was 73 kg·hectare·year−1. Calculated reef production was, therefore, about nine times greater than the production of sand-bottom fish. From 30 to 70% of the four species of tagged fish (sheephead, rock wrasse, black perch, and garibaldi) that could be captured by divers were recaptured after 7 months, indicating a high degree of fidelity to the reef. Recapture of 12% of tagged kelp bass via hook-and-line after 7 months and the recapture of five tagged kelp bass of a total of 40 kelp bass caught 1 year later by a sport fishing boat indicate that kelp bass, too, remained associated with the reef for long periods.
Remote Operated Vehicles are routinely used to undertake inspection and maintenance activities of underwater pipelines in north-west Australia. In doing so, many terabytes of geo-referenced underwater video are collected at depths, and on a scale usually unobtainable for ecological research. We assessed fish diversity and abundance from existing ROV videos collected along 2–3 km sections of two pipelines in north-west Australia, one at 60–80 m water depth and the other at 120–130 m. A total of 5962 individual fish from 92 species and 42 families were observed. Both pipelines were characterised by a high abundance of commercially important fishes including: snappers (Lutjanidae) and groupers (Epinephelidae). The presence of thousands of unidentifiable larval fish, in addition to juveniles, sub-adults and adults suggests that the pipelines may be enhancing, rather than simply attracting, fish stocks. The prevalence and high complexity of sponges on the shallower pipeline and of deepwater corals on the deeper pipeline had a strong positive correlation with the fish abundance. These habitats likely offer a significant food source and refuge for fish, but also for invertebrates upon which fish feed. A greater diversity on the shallower pipeline, and a higher abundance of fishes on both pipelines, were associated with unsupported pipeline sections (spans) and many species appeared to be utilising pipeline spans as refuges. This study is a first look at the potential value of subsea pipelines for fishes on the north-west shelf. While the results suggest that these sections of pipeline appear to offer significant habitat that supports diverse and important commercially fished species, further work, including off-pipeline surveys on the natural seafloor, are required to determine conclusively the ecological value of pipelines and thereby inform discussions regarding the ecological implications of pipeline decommissioning.
It was recently demonstrated that oil platforms are among the most productive marine fish habitats (Claisse et al. in Proc Natl Acad Sci USA 111:15462–15467, 2014). Designed artificial reef systems are similar, albeit smaller, modified habitats designed to accommodate fish assemblages. We compared fish production at a large designed reef to reported production at oil platforms. Given the focus in artificial reef research on distinguishing between new and aggregated fish production, we used a different approach to that of Claisse et al. (Proc Natl Acad Sci USA 111:15462–15467, 2014) to calculate production, based on a steady-state assumption. This assumption simplifies the analysis and distinguishes ‘local production’, ‘new production’, and ‘biomass flux’. Comparing biomass flux with standing stock biomass enables a new approach to address the production versus attraction debate, by revealing how much biomass is exposed to fishing compared to how much has local production. The local fish production at this artificial reef was 384 g m−2 year−1, which is within the 105–887 g m−2 year−1 range reported by Claisse et al., although our study included visitor species not included by Claisse et al. We estimate that the fish production new to the ecosystem may only be 4–5 % of the local production, due to the large abundance of visitor species on this reef. The annual flux of biomass across this reef was very large, ~380 times greater than the standing stock biomass, meaning that this reef is vulnerable to overexploitation from fishing. Our results show that like oil platforms, designed artificial reefs can be very productive marine habitats, but may not greatly increase the net fish production in a system. The method detailed here will allow similar studies to be done relatively simply at other marine habitats, including fish aggregation devices.