Search

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.

Most freshwater fisheries occur in developing countries, where freshwater fish underpin local food security and small-scale fisheries livelihoods. Comprehensive catch data are fundamental to support the sustainable management of freshwater fisheries. However, freshwater catch data reported by the Food and Agriculture Organization of the United Nations (FAO) on behalf of countries under-represent freshwater fisheries because they are dominated by fragmented and highly dispersed small-scale sectors, often with no designated landing sites. Kenya is an emerging economy with socioeconomically important freshwater fisheries and ongoing food security concerns. We undertook a reconstruction of freshwater fisheries catch data for Kenya for the period 1950–2017, aiming to improve the comprehensiveness of existing reported baseline data and to provide a more ecologically and spatially relevant time series dataset for research and management uses. We reconstructed catches for 16 major waterbodies in Kenya and found catches to be 32% higher than the data reported by the FAO on behalf of the country. The subsistence sector (small-scale, non-commercial, personal consumption) accounted for 71% of unreported catches, compared with 29% for artisanal sector catches (small-scale, commercial), suggesting that non-commercial catches for direct local consumption are substantially under-represented in nationally reported statistics and should receive greater attention to support sustainable food security in Kenya.

Freshwater species and habitats are among the most threatened in the world. One way in which this growing conservation concern can be addressed is the creation of freshwater protected areas. Here, we present three strategies for freshwater protected-area design and management: whole-catchment management, natural-flow maintenance, and exclusion of non-native species. These strategies are based on the three primary threats to fresh waters: land-use disturbances, altered hydrologies, and introduction of non-native species. Each strategy draws from research in limnology and river and wetland ecology. Ideally, freshwater protected areas should be located in intact catchments, should have natural hydrological regimes, and should contain no non-native species. Because optimal conservation conditions are often difficult to attain, we also suggest alternative management strategies, including multiple-use modules, use of the river continuum concept, vegetated buffer strips, partial water discharges, and eradication of exotic species. Under some circumstances it may be possible to focus freshwater conservation efforts on two key zones: adjacent terrestrial areas and headwaters.Las especies y hábitats de agua dulce se encuentran entre los más amenazados del mundo. Una forma en la que esta creciente preocupación por la conservación puede ser abordada es la creación de áreas protegidas de agua dulce. Aquí presentamos el diseño de tres áreas protegidas de agua dulce y las estrategias de manejo: manejo global de la cuenca de captación, mantenimiento del flujo natural y exclusión de las especies no nativas. Estas estrategias están basadas en las tres amenazas principales que tienen las aguas dulces: perturbaciones por uso del suelo, hidrologías alteradas e introducciones de especies no nativas. Cada estrategia está planteada como resultado de la investigación en limnología y ecología de ríos y pantanos. Idealmente, las aguas protegidas de agua dulce deberán ser ubicadas en cuencas de captación intactos, que tengan regímenes hidrológicos naturales y que no contengan especies no nativas. Puesto que las condiciones óptimas de conservación son frecuentemente difíciles de alcanzar, también sugerimos estrategias alternativas de manejo que incluyen módulos de uso múltiple, uso del concepto de río continuo, bandas de amortiguamiento con vegetación, descargas parciales de agua y erradicación de especies exóticas. Bajo ciertas circunstancias, puede ser posible enfocar los esfuerzos de conservación de aguas dulces en dos zonas clave: áreas adyacentes terrestres y nacientes.

We calculated extraction and production rates of bushmeat species in two main tropical, moist-for- est regions, the Amazon and Congo basins. Extraction was estimated from the average number of animals consumed per person per year from anthropological studies that reported animal kills brought into settle- ments in the regions. We calculated extraction rates (kg/km 2 /year) for 57 and 31 mammalian taxa in the Congo and Amazon, respectively. We then examined the sustainability of these extraction rates by basin and by taxa, using extraction-to-production ( E:P ) mass-balance equations. Production (tonnes/year) was calculated as the product of r max (the intrinsic rate of natural increase), mammal biomass, and total area of forest in each region. Species exploitation rates at specific body masses were significantly greater in the Congo than in the Amazon. The E:P ratio for the Congo was 2.4, 30 times the Amazon's ratio of 0.081. Thus, Congo Basin mammals must annually produce approximately 93% of their body mass to balance current extraction rates, whereas Amazonian mammals must produce only 4% of their body mass. We calculated sustainability levels derived from Robinson and Redford's harvest model for each taxa. On a basin-wide level, 60% and none of the mammal taxa in the Congo and Amazon basins, respectively, were exploited unsustainably. To evaluate the effect of error on the estimates of E:P , we conducted a sensitivity analysis, which suggests that the mass- balance was most sensitive to error in standing stock but that our results are robust. We estimated that over 5 million tons of wild mammal meat feed millions in Neotropical (0.15 million) and Afrotropical (4.9 mil- lion) forests annually. Our Congo basin estimates are four times higher than those calculated for the region by other workers, and we conclude that the current situation of bushmeat extraction in African rain forests is more precarious than previously thought.

Western Australia's Swan River is a complex asset providing environmental, recreational and commercial benefits. Agencies responsible for its management rely extensively on advice from experts, whose preferences may or may not align with those of the community. Using a choice experiment, we compared public and expert preferences for managing the river's ecology and tested the application of budget‐reallocation and personal‐cost payment vehicles. The results indicate that the budget‐reallocation method is a suitable payment vehicle for public and expert samples, although there are some differences to the more traditional personal‐cost vehicles because of different trade‐offs involved. Modelling revealed heterogeneity in preferences. Expert and public preferences were statistically different from one another at the mean, but a significant amount of heterogeneity existed in the populations sampled. The differences in preferences across both public and expert groups suggest that the measurement of public values for the environment is still an important part of the management process, even when experts are providing advice.

This paper is an output of the Bertarelli Programme in Marine Science, and we are grateful for the Bertarelli Foundation’s support. The pelagic ecosystem is the ocean’s largest by volume and of major importance for food provision and carbon cycling. The high fish species diversity common in the tropics presents a major challenge for biomass estimation using fisheries acoustics, the traditional approach for evaluating mid-water biomass. Converting echo intensities to biomass density requires information on species identity and size, which are typically obtained by lethal means, and thus unsuitable in the portion of the ocean that is ‘no take’. To improve conservation and ecosystem-based management, we present a procedure for determining fish biomass density, using data on species identity, relative abundance, and lengths obtained from stereo baited remote underwater video systems (stereo-BRUVS) to inform the scaling of echosounder survey data (at 38 kHz). We apply the procedure in the British Indian Ocean Territory marine protected area, using acoustic data from 3025 km of survey transects and 546 BRUVS deployments recording relative abundance and size of 12,335 individual fish. Using a Generalised Additive Model of biomass density (GAM, adjR2 = 0.61) we predict, on the basis of oceanographic conditions and bathymetry, that the top 200 m pelagic ecosystem in the Chagos Archipelago, some 118,324 km2, held 3.84 (2.66, 5.62, 95% CI), 33.09 (23.41, 47.35) and 4.08 (3.1, 5.44) million tonnes of fish in November 2012, January 2015, and February 2016, respectively. Our non-extractive procedure yields ecologically credible patterns in biomass across multiple temporal (hours and years) and spatial (metres and kilometres) scales, and marks an improvement on the use of echo intensity alone as a biomass proxy. High seasonal and interannual variability has implication for pelagic fish monitoring. Postprint

Reef sharks may be ecologically redundant, such that other mesopredatory fishes compensate for their functions when they decline in number, preventing trophic cascades. Oral jaw gape, hereafter referred to as gape, determines maximum prey size in many piscivores and therefore affects the size structure of prey assemblages. Here, we examine whether gape and maximum prey size differ between five species of reef shark and 21 species of teleost (n = 754) using data collected from 38 reefs in the Indo-Pacific. Sharks displayed relatively small gape dimensions compared to most teleost species and, at smaller sizes, the giant trevally Caranx ignobilis and other teleosts may be able to consume larger prey than similar-sized sharks. However, ecological redundancy between reef sharks and teleosts appears to decline at larger sizes, such that the grey reef shark Carcharhinus amblyrhynchos, for example, may be capable of consuming larger prey than any other reef predator at its largest sizes, regardless of prey body shape. Moreover, sharks may be able to consume proportionally larger prey as they grow, in contrast to reef teleosts, which may largely be limited by their gapes to ever-smaller prey as a proportion of their body size. Our results also suggest that reef sharks may be unable to swallow whole prey that are > 36% of their length, consistent with gut-content studies. Conservation of reef ecological function may therefore depend not only on the protection of sharks but also particular size classes and key components of the mesopredatory guild.

Environmental conditions strongly influence fish growth and size. Temperature, salinity and oxygen can have negative effects on growth and size when species’ tolerances are exceeded. Climate modelling predicts that persistent oxygen minimum zones (OMZs), where dissolved oxygen concentration is less than 0.5 mll−1, will expand globally, in addition to increases in ocean temperature. The persistent oxygen minimum zone in a warming Arabian Sea is one of only three in the world and, as such, provides a window into the potential responses of fish fauna to decreasing oxygen levels in the global seas. Fork lengths for 19,633 fish of five economically important species (Argyrops spinifer, Drepane longimana, Epinephelus diacanthus, Lethrinus nebulosus and Pomadasys commersonnii) were measured in four regions, during four seasons and at four depth strata in the Arabian Sea in order to test the influence of these factors, as proxies for the OMZ, on mean length and length-frequency distributions. The five species showed three general responses. The first group includes E. diacanthus and P. commersonnii which were largest in the south, largest during the Northeast Monsoon and did not vary in size with depth, possibly taking advantage of rich food sources for recruits but with southern populations associated with the OMZ comprised of larger individuals. The second group was comprised of D. longimana and L. nebulosus which were smaller in shallow depths and showed no influence of region or season and appear relatively insensitive to the OMZ. These two species show typical distribution in relation to depth, with larger individuals found in deeper waters. Finally, A. spinifer, was smallest in the south and in deep waters but showed no effect of season. This may indicate a sensitivity to the OMZ where larger individuals are neither found in the south nor at depth. The results of kernel density estimates largely mirrored these results. The environmental variables were significant but explained little of the deviance in fork length, with the exception of temperature which explained approximately 40% and 26.9% of the variation in length of E. diacanthus and A. spinifer, respectively. These groupings may reflect differential species sensitivities to the OMZ which is strongest in the southern regions during the SW Monsoon. This highlights the need for careful consideration of responses to expanding OMZs, particularly with how this translates into fisheries productivity.

Fish biodiversity is at risk globally due to the climate-driven expansion of areas of low dissolved oxygen. The Arabian Sea is one of the three regions globally with a persistent oxygen minimum zone (OMZ). The Arabian Sea OMZ is a consequence of the high productivity associated with the Southwest Monsoon (SWMon). During the Northeast Monsoon (NEMon), the OMZ is also present but tends to be found in deeper water (>200 m). I examined patterns in fish biodiversity across the Arabian Sea with respect to region, season and depth strata and in relation to environmental conditions, including bottom sea temperature, salinity and dissolved oxygen. Analyses were based on 764 trawl samples collected as part of a stock assessment survey conducted between 2007 and 2008. A total of 99,319 fish were collected, representing 207 species. There was no variation in the estimated total species diversity by region, and the number of species was highest during the NEMon and decreased with greater depth. The average species richness per trawl also did not vary with region and was highest during the NEMon and lowest in the post-Southwest Monsoon (PostMon) period and was greatest in the shallowest depth strata. The Chao1 and Shannon indices of biodiversity showed no regional patterns but were highest in the NEMon and lowest in the SWMon. The analysis also showed declines in these two indices with increasing depth. The total abundance was significantly higher during the PreMon and was invariant in three depth strata 1, 2 and 4 and low in depth strata 3. Biodiversity indices were poorly explained by the environmental variables. Climate change is expected to strengthen the SWMon, which will expand the OMZ. As the SWMon period and its expanded OMZ are associated with lower species richness, biodiversity is likely to be negatively affected by climate change. The generality of this prediction should be evaluated by exploring patterns in biodiversity associated with other OMZs globally and as these features expand through time.

Stereo baited remote underwater video systems (BRUVS) are widely used to document diversity, abundance, and biomass of marine wildlife and record unusual behaviours. We observed a cuttlefish appearing to mimic decapod morphology and locomotion during a non-targeted BRUVS study on Australia’s Northwest Shelf. While the pharaoh cuttlefish Sepia pharaonis (Ehrenberg, 1831) is putatively thought to mimic the appearance of a hermit crab in a laboratory setting, our observation is the first wild record of decapod mimicry by a cuttlefish, tentatively identified as Sepia smithi (Hoyle, 1885). In situ observations increase our understanding of how cuttlefish behave in their natural environment while interacting with other species and provide opportunities to further our understanding of the source and breadth of these mimicry.

Given the recent trend towards establishing very large marine protected areas (MPAs) and the high potential of these to contribute to global conservation targets, we review outcomes of the last decade of marine conservation research in the British Indian Ocean Territory (BIOT), one of the largest MPAs in the world. The BIOT MPA consists of the atolls of the Chagos Archipelago, interspersed with and surrounded by deep oceanic waters. Islands around the atoll rims serve as nesting grounds for sea birds. Extensive and diverse shallow and mesophotic reef habitats provide essential habitat and feeding grounds for all marine life, and the absence of local human impacts may improve recovery after coral bleaching events. Census data have shown recent increases in the abundance of sea turtles, high numbers of nesting seabirds and high fish abundance, at least some of which is linked to the lack of recent harvesting. For example, across the archipelago the annual number of green turtle clutches (Chelonia mydas) is ~ 20,500 and increasing and the number of seabirds is ~ 1 million. Animal tracking studies have shown that some taxa breed and/or forage consistently within the MPA (e.g. some reef fishes, elasmobranchs and seabirds), suggesting the MPA has the potential to provide long-term protection. In contrast, post-nesting green turtles travel up to 4000 km to distant foraging sites, so the protected beaches in the Chagos Archipelago provide a nesting sanctuary for individuals that forage across an ocean basin and several geopolitical borders. Surveys using divers and underwater video systems show high habitat diversity and abundant marine life on all trophic levels. For example, coral cover can be as high as 40–50%. Ecological studies are shedding light on how remote ecosystems function, connect to each other and respond to climate-driven stressors compared to other locations that are more locally impacted. However, important threats to this MPA have been identified, particularly global heating events, and Illegal, Unreported and Unregulated (IUU) fishing activity, which considerably impact both reef and pelagic fishes.

Highlights: • 1st global long-term fishery biomass trends evaluation of 1300 exploited marine populations. • Decline in average fishery biomass observed across oceans and climate zones. • Systemic wide-spread overfishing of the world's coastal and continental shelf water. Abstract: This contribution presents time series of the ‘fishery biomass’ of fish populations, defined as the weight (whole-body, wet weight) of the in-water part of a fishable population, i.e., that part of a population (also called ‘stock’) that is exposed to a certain fishing gear. Detailed data of this type are only available for a limited number of species that are targets of the fisheries in the waters of economically developed regions, such as Europe, the USA, Canada or Australia. However, similar fishery biomass assessments are generally lacking for developing countries, even for many of their most heavily fished species. Here, an estimation of the long-term fishery biomass trends of 1320 fish and invertebrate populations for 483 species exploited by fisheries in the 232 coastal Marine Ecoregions (MEs) around the world was undertaken. Fishery biomass trends were derived using the Bayesian CMSY stock assessment method applied to the global fisheries catch database for 1950–2014 as reconstructed by the Sea Around Us for every maritime fishing country in the world. Overall, the results suggest a consistent decline in the fishery biomass of exploited populations, in virtually all climatic zones and ocean basins in the world. The only zone with currently higher fishery biomass than in 1950 is the northern Pacific polar-boreal zone, likely due to environmental changes that occurred in the region positively affecting fish populations, combined with prudent management of the fisheries. For populations in MEs that are known to have highly questionable catch statistics, the results suggested smaller declines in fishery biomass than likely occurred in reality, implying that these results do not exaggerate declining trends in fishery biomass. This study used informative Bayesian priors to improve the trend analyses in areas where systematic stock assessments were conducted. The use of these independent assessments reduced the uncertainty associated with the findings of this study.

Commercial fisheries catches by countries are documented since 1950 by the Food and Agriculture Organization (FAO). Unfortunately, this does not hold for marine recreational catches, of which only few, if any, estimates are reported to FAO. We reconstructed preliminary estimates of likely marine recreational catches for 1950—2014, based on independent reconstructions for 125 countries. Our estimates of marine recreational catches that are retained and landed increased globally until the early-1980s, stabilized through the 1990s, and began increasing again thereafter, amounting to around 900,000 t·year−1 in 2014. Marine recreational catches thus account for slightly less than 1% of total global marine catches. Trends vary regionally, increasing in Asia, South America and Africa, while slightly decreasing in Europe and Oceania, and strongly decreasing in North America. The derived taxonomic composition indicates that recent catches were dominated by Sparidae (12% of total catches), followed by Scombridae (10%), Carangidae (6%), Gadidae (5%), and Sciaenidae (4%). The importance of Elasmobranchii (sharks and rays) in recreational fisheries in some regions is of concern, given the life-history traits of these taxa. Our preliminary catch reconstruction, despite high data uncertainty, should encourage efforts to improve national data reporting of recreational catches.

Marine fisheries are in crisis, requiring twice the fishing effort of the 1950s to catch the same quantity of fish, and with many fleets operating beyond economic or ecological sustainability. A possible consequence of diminishing returns in this race to fish is serious labour abuses, including modern slavery, which exploit vulnerable workers to reduce costs. Here, we use the Global Slavery Index (GSI), a national-level indicator, as a proxy for modern slavery and labour abuses in fisheries. GSI estimates and fisheries governance are correlated at the national level among the major fishing countries. Furthermore, countries having documented labour abuses at sea share key features, including higher levels of subsidised distant-water fishing and poor catch reporting. Further research into modern slavery in the fisheries sector is needed to better understand how the issue relates to overfishing and fisheries policy, as well as measures to reduce risk in these labour markets., There have been growing concerns about the exploitation of workers in the fisheries sectors. Here, Tickler et al. use a country-level metric of slavery to determine the risk of fisheries-level slavery across 20 countries, and find it rises as unreported catch increases and mean value of catch decreases.

Entrainment of growth patterns of multiple species to single climatic drivers can lower ecosystem resilience and increase the risk of species extinction during stressful climatic events. However, predictions of the effects of climate change on the productivity and dynamics of marine fishes are hampered by a lack of historical data on growth patterns. We use otolith biochronologies to show that the strength of a boundary current, modulated by the El Niño-Southern Oscillation, accounted for almost half of the shared variance in annual growth patterns of five of six species of tropical and temperate marine fishes across 23° of latitude (3000 km) in Western Australia. Stronger flow during La Niña years drove increased growth of five species, whereas weaker flow during El Niño years reduced growth. Our work is the first to link the growth patterns of multiple fishes with a single oceanographic/climate phenomenon at large spatial scales and across multiple climate zones, habitat types, trophic levels and depth ranges. Extreme La Niña and El Niño events are predicted to occur more frequently in the future and these are likely to have implications for these vulnerable ecosystems, such as a limited capacity of the marine taxa to recover from stressful climatic events.

We thank the Western Australian Departments of Fisheries, Parks and Wildlife (DPaW), the Commonwealth Department of Sustainability, Environment, Water, Population and Communities for arranging permits to conduct research at the Scott Reefs and the Rowley Shoals. We acknowledge the crew on board the RV 'Solander,' Kim Brooks, Paul Tinkler and numerous volunteers for aid in the field. Thanks also to Paddy Ryan who provided images for the figures. Special thanks to Sarah Hirth, Gammon Koval, Rachel Skubel and Marcelo Costa Lopez for help with some figures. This research was funded in part by the Australian Institute of Marine Science, an International Postgraduate Research Scholarship to S.C.B., the Save our Seas Foundation and the University of Western Australia, Perth, under UWA Ethics Approvals: RA3/100/1279, RA3/100/1172. We thank Ashley Frisch and several reviewers who provided valuable comments that improved our manuscript.

Aim Protected areas have become pivotal to the modern conservation planning toolbox, but a limited understanding of marine macroecology is hampering their efficient design and implementation in pelagic environments. We explored the respective contributions of environmental factors and human impacts in capturing the distribution of an assemblage of commercially valuable, large-bodied, open-water predators (tunas, marlins and mackerels). Location Western Australia. Time period 1997–2006. Major taxa studied Pelagic fishes. Methods We compiled 10 years of commercial fishing records from the Sea Around Us Project and derived relative abundance indices from standardized catch rates while accounting for confounding effects of effort, year and gear type. We used these indices to map pelagic hotspots over a 0.5°-resolution grid and built random forests to estimate the importance of 33 geophysical, oceanographic and anthropogenic predictors in explaining their locations. We additionally examined the spatial congruence between these hotspots and an extensive network of marine reserves and determined whether patterns of co-occurrence deviated from random expectations using null model simulations. Results First, we identified several pelagic hotspots off the coast of Western Australia. Second, geomorphometrics explained up to 50% of the variance in relative abundance of pelagic fishes, and submarine canyon presence ranked as the most influential variable in the North bioregion. Seafloor complexity, geodiversity, salinity, temperature variability, primary production, ocean energy, current regimes and human impacts were also identified as important predictors. Third, spatial overlap between hotspots and marine reserves was limited, with most high-abundance areas primarily found in zones where anthropogenic activities are subject to few regulations. Main conclusions This study reveals geomorphometrics as valuable indicators of the distribution of mobile fish species and highlights the relevance of harnessing static topography as a key element in any blueprint for ocean zoning and spatial management.

Tiger sharks were sampled off the western (Ningaloo Reef, Shark Bay) and eastern (the Great Barrier Reef; GBR, Queensland and New South Wales; NSW) coastlines of Australia. Multiple tissues were collected from each shark to investigate the effects of location, size and sex of sharks on δ13C and δ15N stable isotopes among these locations. Isotopic composition of sharks sampled in reef and seagrass habitats (Shark Bay, GBR) reflected seagrass-based food-webs, whereas at Ningaloo Reef analysis revealed a dietary transition between pelagic and seagrass food-webs. In temperate habitats off southern Queensland and NSW coasts, shark diets relied on pelagic food-webs. Tiger sharks occupied roles at the top of food-webs at Shark Bay and on the GBR, but not at Ningaloo Reef or off the coast of NSW. Composition of δ13C in tissues was influenced by body size and sex of sharks, in addition to residency and diet stability. This variability in stable isotopic composition of tissues is likely to be a result of adaptive foraging strategies that allow these sharks to exploit multiple shelf and offshore habitats. The trophic role of tiger sharks is therefore both context- and habitat-dependent, consistent with a generalist, opportunistic diet at the population level.

We thank the University of Western Australia (UWA), Perth, which partly funded this research via an International Postgraduate Research Scholarship and the Australian Institute of Marine Science. We also thank the Department of Fisheries, the Department of Parks and Wildlife (DPaW) and the Department of Sustainability, Environment, Water, Population and Communities for arranging permits to conduct research at the Scott Reefs and the Rowley Shoals. Thank you also to the crew on board the RV 'Solander'. This research was permitted under UWA Ethics Approvals: RA3/100/1279, RA3/100/1172.

Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark-monitoring data on large scales (100s–1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of the occurrence of juvenile shark habitat. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef [Triaenodon obesus]. We predicted the occurrence of juvenile sharks across 490,515 km2 of coastal waters and quantified the representation of highly suitable habitats within MPAs. Our species-level models had higher accuracy (ĸ ≥ 0.69) and deviance explained (≥ 48 %) than our order-level model (ĸ = 0.36 and deviance explained of 10 %). Maps of predicted occurrence revealed different species-specific patterns of highly suitable habitat. These differences likely reflect different physiological or resource requirements between individual species and validate concerns over the utility of conservation targets based on aggregate species groups as opposed to a species-focused approach. Highly suitable habitats were poorly represented in MPAs with the most restrictions on extractive activities. This spatial mismatch possibly indicates a lack of explicit conservation targets and information on species distribution during the planning process. The nonextractive BRUVS provided a useful platform for building the suitability models across large scales to assist conservation planning across multiple maritime jurisdictions, and our approach provides a simple for method for testing the effectiveness of MPAs. This article is protected by copyright. All rights reserved

Biochronologies provide important insights into the growth responses of fishes to past variability in physical and biological environments and, in so doing, allow modelling of likely responses to climate change in the future. We examined spatial variability in the key drivers of inter-annual growth patterns of a widespread, tropical snapper, Lutjanus bohar, at similar tropical latitudes on the north-western and north-eastern coasts of the continent of Australia. For this study, we developed biochronologies from otoliths that provided proxies of somatic growth and these were analysed using mixed-effects models to examine the historical drivers of growth. Our analyses demonstrated that growth patterns of fish were driven by different climatic and biological factors in each region, including Pacific Ocean climate indices, regional sea level and the size structure of the fish community. Our results showed that the local oceanographic and biological context of reef systems strongly influenced the growth of L. bohar and that a single age-related growth trend cannot be assumed for separate populations of this species that are likely to experience different environmental conditions. Generalised predictions about the growth response of fishes to climate change will thus require adequate characterisation of the spatial variability in growth determinants likely to be found throughout the range of species that have cosmopolitan distributions.

Offshore oil and gas platforms are found on continental shelves throughout the world’s oceans. Over the course of their decades-long life-spans, these platforms become ecologically important artificial reefs, supporting a variety of marine life. When offshore platforms are no longer active they are decommissioned, which usually requires the removal of the entire platform from the marine environment, destroying the artificial reef that has been created and potentially resulting in the loss of important ecosystem services. While some countries allow for these platforms to be converted into artificial reefs under Rigs-to-Reefs programs, they face significant resistance from various stakeholders. The presence of offshore platforms and the associated marine life alters the ecosystem from that which existed prior to the installation of the platform, and there may be factors which make restoration of the ecosystem unfeasible or even detrimental to the environment. In these cases, a novel ecosystem has emerged with potentially significant ecological value. In restoration ecology, ecosystems altered in this way can be classified and managed using the novel ecosystems concept, which recognizes the value of the new ecosystem functions and services and allows for the ecosystem to be managed in its novel state, instead of being restored. Offshore platforms can be assessed under the novel ecosystems concept using existing decommissioning decision analysis models as a base. With thousands of platforms to be decommissioned around the world in coming decades, the novel ecosystems concept provides a mechanism for recognizing the ecological role played by offshore platforms.

Since the 1950s, industrial fisheries have expanded globally, as fishing vessels are required to travel further afield for fishing opportunities. Technological advancements and fishery subsidies have granted ever-increasing access to populations of sharks, tunas, billfishes, and other predators. Wilderness refuges, defined here as areas beyond the detectable range of human influence, are therefore increasingly rare. In order to achieve marine resources sustainability, large no-take marine protected areas (MPAs) with pelagic components are being implemented. However, such conservation efforts require knowledge of the critical habitats for predators, both across shallow reefs and the deeper ocean. Here, we fill this gap in knowledge across the Indo-Pacific by using 1,041 midwater baited videos to survey sharks and other pelagic predators such as rainbow runner (Elagatis bipinnulata), mahi-mahi (Coryphaena hippurus), and black marlin (Istiompax indica). We modeled three key predator community attributes: vertebrate species richness, mean maximum body size, and shark abundance as a function of geomorphology, environmental conditions, and human pressures. All attributes were primarily driven by geomorphology (35%-62% variance explained) and environmental conditions (14%-49%). While human pressures had no influence on species richness, both body size and shark abundance responded strongly to distance to human markets (12%-20%). Refuges were identified at more than 1,250 km from human markets for body size and for shark abundance. These refuges were identified as remote and shallow seabed features, such as seamounts, submerged banks, and reefs. Worryingly, hotpots of large individuals and of shark abundance are presently under-represented within no-take MPAs that aim to effectively protect marine predators, such as the British Indian Ocean Territory. Population recovery of predators is unlikely to occur without strategic placement and effective enforcement of large no-take MPAs in both coastal and remote locations.

Within atolls, deep water channels exert significant control over local hydrodynamic conditions; which are important drivers of planktonic distributions. To examine planktonic responses to oceanography, this study tested the effect of proximity and exposure to deep oceanic flushing through these channels on water properties and planktonic assemblages across four atolls (Diego Garcia, Salomon, Egmont, and Peros Banhos) in the British Indian Ocean Territory Marine Reserve. As this is the largest, most isolated and sparsely inhabited atoll complex in the world, it provides the perfect experimental conditions to test the effect of oceanic flushing without confounding factors related to anthropogenic development. Results are discussed in the context of ecosystem functioning. A total of 30 planktonic taxa and 19,539 individuals were identified and counted. Abundance was significantly different between atolls and significantly greater within inner regions in all atolls except southeast Egmont. Planktonic assemblage composition significantly differed between atolls and between inner and outer stations; exhibiting higher similarity between outer stations. Within outer stations of Diego Garcia, Peros Banhos, and Egmont, evidence suggesting oceanic flushing of cold, saline, and dense water was observed, however a longer time series is required to conclusively demonstrate tidal forcing of this water through deep water channels. Planktonic variability between inner and outer atoll regions demonstrates that broad comparisons between oceanic and lagoon regions fail to capture the complex spatial dynamics and hydrodynamic interactions within atolls. Better comprehension of these distributional patterns is imperative to monitor ecosystem health and functioning, particularly due to increasing global anthropogenic pressures related to climate change. The extensive coral bleaching described in this paper highlights this concern.