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.
•Stereo-BRUVs and Stereo-ROV sampled different compositions of fish on and off the pipeline.•Stereo-ROV may under-sample fish in open sandy habitats.•Stereo-BRUVs may over-sample fine-scale habitat associations due to bait attraction.•Stereo-ROV samples fish-habitat associations in greater detail.•Stereo-ROV is a more suitable tool for sampling fish on pipeline and fine-scale structures.
There has been rapid uptake of stereo‐video‐based sampling techniques to collect species, abundance and body‐size information on fish assemblages and their associated habitats. Stereo‐video methods ...provide highly accurate estimates of body‐size, range and sampling area as well as a permanent record that can be cross‐checked or resampled for additional data. Due to these advantages, diver‐operated stereo‐video (stereo‐DOV) is becoming an increasingly popular alternative to underwater visual census.
We provide a comprehensive guide for researchers using stereo‐DOVs to survey fish assemblages and their associated habitat. Information on stereo‐DOV design, video camera settings, field operations and video analysis are outlined.
Stereo–DOV surveys permit rapid and simultaneous collection of data on fish diversity, abundance, length and behaviour as well as their associated habitat. However, biases associated with diver presence in the water and variation in detectability should be considered and are dependent on the location and focal species of the survey.
We recommend using stereo‐DOVs for diver‐based surveys of non‐cryptic fish assemblages, given the advantages described. An increased uptake of this methodology, following the standard procedures described herein, will reduce variation in methodology, assist in the synthesis of data on continental and global scales and provide accurate information to improve fisheries management and conservation.
Invasive marine species (IMS) are a major anthropogenic threat to global marine environments. To mitigate the threat, Australian federal and state governments have developed detailed quarantine ...programs to minimise IMS introductions, supported by monitoring programs to detect any IMS that penetrated the quarantine barriers. Considerable shipping movements occur between the Pilbara region of northwestern Australia and southeast Asia where a number of potential IMS oysters occur. eDNA techniques are being developed to rapidly scan biofouling and other samples for potential IMS, but there is limited information on oysters present in the Pilbara. We collected intertidal oysters in and near Pilbara ports and identified them using DNA sequences to determine if any IMS are present and to provide a baseline to prevent false positive results for IMS by native species. Only three species were detected: native Saccostrea lineage A and S. scyphophilla, both widespread in the Pilbara, and Talonostrea sp. nov. which had not previously been reported from the Pilbara. No IMS oysters were found. The study provides a solid basis for monitoring for any future occurrences of IMS oyster species in the Pilbara, an area with a very high known shallow water marine biodiversity, but where only a single IMS is known to occur.
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.
There is growing interest in understanding the ecological benefits of oil and gas structures. This is the first reported case of the spawning aggregation and mating behaviour of bigeye trevally, ...Caranx sexfasciatus, associated with an oil and gas platform, demonstrating that oil and gas jackets are capable of not only attracting large aggregations of fish, but can provide suitable conditions for reproductive purposes. Fish spawning aggregations (FSAs) are highly vulnerable events that are vitally important for the persistence of many fish species. Urgent protection and conservation of FSA sites is required to secure them from the threat of overfishing. The findings of this study bring into question the management strategies required for oil and gas structures, particularly related to removal during decommissioning, or where structures are left in place and safety exclusion zones no longer apply. These aggregations and behaviours were captured using underwater stereo-video Remotely Operated Vehicle (ROV) methods, allowing for detailed observations.
•Bigeye trevally, Caranx sexfasciatus, were observed spawning at an oil and gas platform jacket in the Gulf of Thailand.•The platform is likely to have site characteristics conducive to spawning for multiple species, similar to a “pinnacle”.•Trevally were observed spawning on the later side of the wider regional spawning period.•Fertilised eggs and larvae may travel to the nearby natural reef (∼150 km away) or mangroves.•Findings of this study contribute to the increasing evidence base that oil and gas platforms provide ecological value.
Decommissioning of offshore oil and gas structures is either occurring, or imminent in most regions of the world. Most jurisdictions require that offshore structures be removed for onshore disposal. ...However, there is growing interest in understanding the ecological and socio-economic benefits of leaving structures in the water. Descriptions of how fish utilize the vertical structure created by wellhead platform jackets (platforms) will provide insights into possible outcomes of decommissioning alternatives, such as full removal, leave
in situ
, or translocation to a designated reefing site. We surveyed fish assemblages associated with seven platforms and five reference sites located ∼150 km offshore in the central Gulf of Thailand. The platforms spanned the entire water column (∼75 m) and were a mix of three and four legged structures. We used a Remotely Operated Vehicle (ROV) fitted with an underwater stereo video system to quantify the abundance, size, biomass, and economic value of fish associated with the platforms. We recorded 43 species of fish on the platforms and five reference sites with most fishes on platforms categorized as coral-reef or coral-reef-associated species. We observed a strong vertical zonation in the fish assemblage on the platforms. The Regal demoiselle (
Neopomacentrus cyanomos
) was numerically dominant (75% of all fish observed). We measured 3,933 kg of fish on the platforms with
Caranx sexfasciatus
accounting for 76.12% of that. We conservatively estimate each platform had a scaled mean biomass of ∼2,927 kg and the fished species had scaled mean economic value of 175,500 Thai Baht per platform. We estimated that the biomass of fish associated with the seven platforms was at least four times higher per unit area than some of the world’s most productive coral reefs.
We investigated the composition and abundance of fish assemblages associated with seven offshore oil and gas platform jackets in the Gulf of Thailand before (pre-lift and pre-tow), and immediately ...after relocation (post-tow and reefed). Jackets were cut, lifted until partly out of the water, and attached to the rear of a heavy lift vessel. They were towed at speeds of 2.7 – 3.3 knots for between 133.9 and 205.4 km before being placed on the seafloor at an artificial reef site. Sixteen species of fish were observed both before and after jacket towing. We believe these species have sought refuge in the complex structures out of the current and have remained with the jackets. Ten species of fish were observed before towing, but not after. A further seven species of fish were only observed after the jackets were relocated onto the seafloor and were assumed to be early colonisers to the structures. The paper provides empirical evidence of a much-discussed paradigm that fish can swim great distances following moved structures, and further evidence of the ability of fish to rapidly colonise reefed structures.
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•Fish on oil and gas jackets were surveyed before, during and after towing.•16 species of fish remained with the jackets during relocation (followers).•10 species of fish did not follow the jackets (deserters).•7 new species of fish were observed (colonisers) within two days of placement of jackets on the seabed.•“Followers” likely sought refuge in the complex structures out of the current during towing.
Information on the contribution of offshore oil and gas (O&G) platforms to fish productivity is required to contribute to the decision-making process to remove, partially remove, or retain these ...structures during decommissioning after petroleum production ceases. The present study assesses the biomass and fish production of one common and abundant fish species (Caesioperca lepidoptera – butterfly perch) and two commercially fished species (Helicolenus percoides – reef ocean perch; Nemadactylus macropterus – jackass morwong) on eight O&G platforms and in surrounding natural habitats in the Bass Strait, south-east Australia, where options for decommissioning are being assessed. High-definition stereo-video imagery was collected by remotely operated vehicle (ROV) from eight platform facilities, their immediate benthic surrounds, reference areas reflective of the likely pre-installation seabed state (sand-dominated) and a nearby natural ‘reef’ area referred to as south-east reef (some limestone foundation). The biomass of all three species was low in the benthic surrounds of platforms, at reference locations and at south-east reef where minimal cover by benthic organisms was recorded and, as such, there was little to no fish production for the three study species in these areas. We observed a total fish biomass of 2.85 tonnes across the eight platforms for the three fish species surveyed, with high variability across platforms. Total production (P) across all platforms was estimated at 1244 kg/year for the three species, with a mean fish production density of 82 g/m2/year. Approximately 79% of total production is considered ‘new’ production (984 kg/year i.e., the production attributed to the presence of the platforms; with a mean production density of 64 g/m2/year). The remaining 21% could be retained or redistributed into the surrounding area if platforms were removed. C. lepidoptera accounted for the majority (90%) of biomass and of total production for all three species across all locations surveyed. Despite only accounting for a small proportion of platform surface area, the bottom 5 m sections of platforms had 41% of the total biomass observed and accounted for 46% of total production of these three study species. Production measures for platforms surveyed here are relatively high compared to other artificial reefs and habitats around the world. Total removal of these platforms will likely result in a reduction of fish biomass and fish productivity (incl. several fishery species) in the immediate vicinity.
•Platforms promote fish diversity and abundance in areas where it would be otherwise be minimal.•Platform production measures were relatively high compared to other artificial reefs and habitats around the world.•The bottom 5 m sections of platforms contained 41% of the total biomass observed and accounted for 46% of total production.•Complete removal of infrastructure would likely eliminate most fish production at that location.
Subtidal research presents numerous challenges that restrict the ability to answer fundamental ecological questions related to reef systems. These challenges are closely associated with traditional ...monitoring methods and include depth restrictions (e.g. safe diving depths for underwater visual census), habitat destruction (e.g. trawling), mortality of target species (e.g. controlled angling and fish traps), and high operating costs (e.g. remotely operated vehicles and large research vessels). Whereas many of these challenges do not apply or are avoidable in the shallow subtidal environment, the difficulties grow as one attempts to sample deeper benthic habitats. This situation has resulted in a paucity of knowledge on the structure and ecology of deep water reef habitats around the coast of South Africa, and in most marine areas around the world. Furthermore, the inability to effectively survey deep water benthic environments has limited the capacity of researchers to investigate connectivity between shallow and deep water habitats in a standardised and comparable fashion.
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