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Understanding population structure is important for predicting the outcomes of anthropogenic development, harvest, and environmental change on the abundance of fisheries species. Logically, the use of several data sources is best for delineating population structure, but combining across data types adds extra challenges as results can be incongruent. Here, genetic and environmental markers were used to test hypotheses about population structure in a collection of 523 tropical inshore finfish (Lutjanus johnii) across northern Australia from 20 locations. Redundancy analyses (RDA) were used to statistically test for correlations among data sources providing a basis for reconciliation and insights into ecological and evolutionary processes. Genomic data (10349 SNP loci) revealed low, but significant genetic divergence (max FST 0.0402) between 16 locations. A total of 12 putative contiguous biological stocks were proposed whose distributions were correlated with IMCRA bioregions but not to existing regions used for management of the fishery. RDA showed a significant correlation between environmental markers (otolith chemistry and parasite abundances) and SNP genotype in two of three region-wide analyses supporting the proposed stock structure, and suggesting that L. johnii may be locally adapted to the heterogeneous environment. These findings are significant for the conservation of the commercially and recreationally important L. johnii and can be used to guide future fisheries management actions.

The mechanisms that govern fauna-habitat associations across multiple spatial scales remain largely undefined. Can environmental factors structure fauna-habitat associations over both local and global spatial scales, alongside biogeographical processes and patterns? We compare the extent to which the use of mangroves by fishes is consistent within and between biogeographic locations, and whether any similarities and differences can be attributed to the environmental context of those forests, such as the physical environment, seascape composition and constraints on access by fishes. We focus on three important proxies of these structuring forces for fish—salinity, distance to reefs and tidal amplitude. Using directly comparable remote underwater visual census from a range of diverse environmental contexts in the Central and Eastern Indo-Pacific, we examine similarity in the family-level taxonomic composition of fish assemblages in mangrove forests. Local environmental context appears to explain similarities and differences in mangrove association by fishes at both regional and local scales across the Indo-Pacific. There were strong consistencies in taxonomic composition in similar environmental contexts despite geographic separation. Tidal amplitude was a powerful explanatory factor that interacted with both distance to reef and salinity in partitioning variation in fish assemblage structure. Substantial differences in the use of mangroves between regions appear to be independent of historical biogeography, relating instead to local context. Our findings suggest that the effects of local context on habitat suitability can play out over biogeographical scales, and global similarities in fauna-habitat associations may be partially explained by comparable environmental contexts, with important management implications.

Environmental DNA (eDNA) metabarcoding, a technique for retrieving multispecies DNA from environmental samples, can detect a diverse array of marine species from filtered seawater samples. There is a growing potential to integrate eDNA alongside existing monitoring methods in order to establish or improve the assessment of species diversity. Remote island reefs are increasingly vulnerable to climate-related threats and as such there is a pressing need for cost-effective whole-ecosystem surveying to baseline biodiversity, study assemblage changes and ultimately develop sustainable management plans. We investigated the utility of eDNA metabarcoding as a high-resolution, multitrophic biomonitoring tool at the Cocos (Keeling) Islands, Australia (CKI)-a remote tropical coral reef atoll situated within the eastern Indian Ocean. Metabarcoding assays targeting the mitochondrial 16S rRNA and CO1 genes, as well as the 18S rRNA nuclear gene, were applied to 252 surface seawater samples collected from 42 sites within a 140 km2 area. Our assays successfully detected a wide range of bony fish and elasmobranchs (244 taxa), crustaceans (88), molluscs (37) and echinoderms (7). Assemblage composition varied significantly between sites, reflecting habitat partitioning across the island ecosystem and demonstrating the localisation of eDNA signals, despite extensive tidal and oceanic movements. In addition, we document putative new occurrence records for 46 taxa and compare the efficiency of our eDNA approach to visual survey techniques at CKI. Our study demonstrates the utility of a multimarker metabarcoding approach in capturing multitrophic biodiversity across an entire coral reef atoll and sets an important baseline for ongoing monitoring and management.

Aim To determine the impact of ecological and environmental histories on the evolution of coral reef damselfishes at two adjacent marine biogeographic suture zones. Location Indo-West Pacific, notably including two suture zones: Socotra and Christmas and Cocos/Keeling Islands. Taxon Chromis dimidiata, Chromis margaritifer, and Chromis fieldi. Methods We utilized a combination of nuclear and mitochondrial genetic markers in addition to visual abundance survey data of these fishes. Results Despite genetic patterns consistent with incomplete lineage sorting and relatively low genetic differentiation among the three studied Chromis species, there is evidence of hybridization between C. margaritifer and C. fieldi at Christmas Island based on molecular and visual identification. Introgression appears to be spreading westwards to other C. fieldi populations based on COI haplotype comparison. Moreover, the genetic distance between C. margaritifer and C. fieldi suggests that Pleistocene sea-level fluctuations may have contributed to allopatric divergence and secondary contact between these two closely related species. Main conclusions Our study highlights that evolutionary processes in coral reef fishes operate differently between suture zones, possibly due to different ecological and environmental predispositions regulating secondary contact of sister species. While secondary contact likely led to hybridization and introgression at Christmas and Cocos/Keeling Islands, none of those processes seem present at Socotra for the chocolate-dipped damselfish. This difference is likely due to an environmental barrier caused by hydrodynamic regimes in the Gulf of Aden.

Coral reef health and biodiversity is under threat worldwide due to rapid climate change. However, much of the inter- and intra-specific diversity of coral reefs are undescribed even in well studied taxa such as fish. Delimiting previously unrecognised diversity is important for understanding the processes that generate and sustain biodiversity in coral reef ecosystems and informing strategies for their conservation and management. Many taxa that inhabit geographically isolated coral reefs rely on self-recruitment for population persistence, providing the opportunity for the evolution of unique genetic lineages through divergent selection and reproductive isolation. Many such lineages in corals and fish are morphologically similar or indistinguishable. Here, we report the discovery and characterisation of cryptic lineages of the Wolf Cardinalfish, Cheilodipterus artus, from the coral atolls of northwest Australia using multiple molecular markers from mitochondrial (CO1 and D-loop) and nuclear (microsatellites) DNA. Concordant results from all markers identified two highly divergent lineages that are morphologically cryptic and reproductively isolated. These lineages co-occurred at daytime resting sites, but the relative abundance of each lineage was strongly correlated with wave exposure. It appears, therefore, that fish from each lineage are better adapted to different microhabitats. Such cryptic and ecologically based diversity appears to be common in these atolls and may well aid resilience of these systems. Our results also highlight that underwater surveys based on visual identification clearly underestimate biodiversity, and that a taxonomic revision of the Cheilodipterus genus is necessary.

Marine fisheries in coastal ecosystems in many areas of the world have historically removed large-bodied individuals, potentially impairing ecosystem functioning and the long-term sustainability of fish populations. Reporting on size-based indicators that link to food-web structure can contribute to ecosystem-based management, but the application of these indicators over large (cross-ecosystem) geographical scales has been limited to either fisheries-dependent catch data or diver-based methods restricted to shallow waters (20 m) that can misrepresent the abundance of large-bodied fished species. We obtained data on the body-size structure of 82 recreationally or commercially targeted marine demersal teleosts from 2904 deployments of baited remote underwater stereo-video (stereo-BRUV). Sampling was at up to 50 m depth and covered approximately 10,000 km of the continental shelf of Australia. Seascape relief, water depth, and human gravity (i.e., a proxy of human impacts) were the strongest predictors of the probability of occurrence of large fishes and the abundance of fishes above the minimum legal size of capture. No-take marine reserves had a positive effect on the abundance of fishes above legal size, although the effect varied across species groups. In contrast, sublegal fishes were best predicted by gradients in sea surface temperature (mean and variance). In areas of low human impact, large fishes were about three times more likely to be encountered and fishes of legal size were approximately five times more abundant. For conspicuous species groups with contrasting habitat, environmental, and biogeographic affinities, abundance of legal-size fishes typically declined as human impact increased. Our large-scale quantitative analyses highlight the combined importance of seascape complexity, regions with low human footprint, and no-take marine reserves in protecting large-bodied fishes across a broad range of species and ecosystem configurations.Las pesquerías marinas de los ecosistemas costeros en muchas áreas del mundo históricamente han removido a individuos de gran tamaño, potencialmente perjudicando el funcionamiento ambiental y la sostenibilidad a largo plazo de las poblaciones de peces. Los reportes sobre los indicadores basados en el tamaño que se vinculan con la estructura de la red alimenticia pueden contribuir al manejo basado en el ecosistema, aunque la aplicación de estos indicadores a grandes (inter-ecosistemas) escalas geográficas ha estado limitada a datos de captura dependientes de las pesquerías o métodos basados en el buceo restringidos a aguas someras (20 m), lo cual puede representar erróneamente la abundancia de peces de gran tamaño capturados para la pesca. Obtuvimos los datos de la estructura del tamaño corporal de 82 teleósteos marinos demersales focalizados por razones recreativas o comerciales tomados de 2,904 despliegues de video estéreo subacuático remoto con cebo (stereo-BRUV, en inglés). El muestreo se realizó hasta los 50 metros de profundidad y abarcó aproximadamente 10,000 km del talud continental de Australia. El relieve marino, la profundidad del agua y la gravedad humana (es decir, un indicador de los impactos humanos) fueron los pronosticadores más sólidos de la probabilidad de incidencia de los peces de gran tamaño y de la abundancia de peces por encima del tamaño legal mínimo de captura. Las reservas marinas de protección total tienen un efecto positivo sobre la abundancia de los peces que están por encima del tamaño legal, aunque el efecto varió según el grupo de especies. Como contraste, los peces de tamaño sublegal fueron pronosticados de mejor manera usando gradientes de la temperatura de la superficie marina (media y varianza). En las áreas con un impacto humano reducido, los peces de gran tamaño corporal tenían hasta tres veces mayor probabilidad de aparecer y los peces de tamaño legal eran aproximadamente cinco veces más abundantes. Para los grupos de especies conspicuas con afinidades contrastantes de hábitat, ambiente y biogeografía, la abundancia de peces de tamaño legal normalmente declinó conforme aumentó el impacto humano. Nuestros análisis cuantitativos a gran escala resaltan la importancia conjunta que tienen la complejidad marina, las regiones con una huella humana reducida y las reservas marinas de protección total para la protección de los peces de gran tamaño corporal en una extensa gama de especies y configuraciones ecosistémicas. Efectos de la Huella Humana y los Factores Biofísicos sobre la Estructura del Tamaño Corporal de Especies Marinas Capturadas para la Pesca.

Marine reserves are a key tool for the conservation of marine biodiversity, yet only ~2.5% of the world's oceans are protected. The integration of marine reserves into connected networks representing all habitats has been encouraged by international agreements, yet the benefits of this design has not been tested empirically. Australia has one of the largest systems of marine reserves, providing a rare opportunity to assess how connectivity influences conservation success. An Australia‐wide dataset was collected using baited remote underwater video systems deployed across a depth range from 0 to 100 m to assess the effectiveness of marine reserves for protecting teleosts subject to commercial and recreational fishing. A meta‐analytical comparison of 73 fished species within 91 marine reserves found that, on average, marine reserves had 28% greater abundance and 53% greater biomass of fished species compared to adjacent areas open to fishing. However, benefits of protection were not observed across all reserves (heterogeneity), so full subsets generalized additive modelling was used to consider factors that influence marine reserve effectiveness, including distance‐based and ecological metrics of connectivity among reserves. Our results suggest that increased connectivity and depth improve the aforementioned marine reserve benefits and that these factors should be considered to optimize such benefits over time. We provide important guidance on factors to consider when implementing marine reserves for the purpose of increasing the abundance and size of fished species, given the expected increase in coverage globally. We show that marine reserves that are highly protected (no‐take) and designed to optimize connectivity, size and depth range can provide an effective conservation strategy for fished species in temperate and tropical waters within an overarching marine biodiversity conservation framework., An Australia‐wide dataset was collected using baited remote underwater video systems deployed across a depth range from 0 to 100 m to assess the effectiveness of marine reserves for protecting fished species. A meta‐analytical comparison of 73 fished species within 91 marine reserves found that, on average, marine reserves had 28% greater abundance and 53% greater biomass of fished species compared to adjacent areas open to fishing. We show that marine reserves that are highly protected (no‐take) and designed to optimize connectivity, size and depth range can provide an effective conservation strategy for fished species in temperate and tropical waters.

Made available in DSpace on 2021-06-25T12:19:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-24 Australian Government's National Environmental Science Program Australian Research Data Commons GorgonBarrow Island Gorgon Barrow Island Net Conservation Benefits Fund 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. Univ Western Australia, UWA Oceans Inst, Perth, WA, Australia Univ Western Australia, Sch Biol Sci, Perth, WA, Australia Dept Biodivers Conservat & Attract, Marine Sci Program, Biodivers & Conservat Sci, Kensington, WA, Australia Curtin Univ, Sch Mol & Life Sci, Perth, WA, Australia Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia Silliman Univ, Angelo King Ctr Res & Environm Management, Dumaguete, Philippines NOAA Inouye Reg Ctr, NOAA Fisheries, Pacific Isl Fisheries Sci Ctr, Sci Operat Div, Honolulu, HI USA Univ Hawaii Manoa, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA South African Inst Aquat Biodivers, Grahamstown, South Africa Rhodes Univ, Dept Zool & Entomol, Grahamstown, South Africa Univ St Andrews, Ctr Res Ecol & Environm Modelling, Sch Math & Stat, St Andrews, Fife, Scotland Indian Ocean Marine Res Ctr, Australian Inst Marine Sci, Perth, WA, Australia Australian Inst Marine Sci, Townsville, Qld, Australia Govt Western Australia, Western Australian Fisheries & Marine Res Labs, Dept Primary Ind & Reg Dev, North Beach, WA, Australia NSW Dept Primary Ind, Fisheries Res, Taylors Beach, NSW, Australia Dept Environm & Water, Marine Sci Program, Sci & Corp Serv Div, Adelaide, SA, Australia Flinders Univ S Australia, Southern Shark Ecol Grp, Coll Sci & Engn, Bedford Pk, SA, Australia Deakin Univ, Sch Life & Environm Sci, Ctr Integrat Ecol, Warrnambool, Vic, Australia NSW Dept Primary Ind, Fisheries Res, Huskisson, NSW, Australia Coral Reef Res Fdn, Koror, Palau NSW Dept Primary Ind, Fisheries Res, Coffs Harbour, NSW, Australia Ctr Environm Fisheries & Aquaculture Sci, Lowestoft, Suffolk, England Sao Paulo State Univ, Elasmobranch Res Lab, Inst Biosci, Sao Vicente, SP, Brazil Massey Univ, Sch Nat & Computat Sci, Auckland, New Zealand Sao Paulo State Univ, Elasmobranch Res Lab, Inst Biosci, Sao Vicente, SP, Brazil

Genetic diversity and connectivity are key factors in determining a population’s resilience to future disturbance. This is especially relevant to corals, which are in global decline due to increasing frequency and strength of thermal anomalies and severe tropical cyclones. While many studies have investigated genetic diversity and population structure in corals, they focused on species being removed at the greatest rate from coral reefs, acroporids and pocilloporids, and it is unclear whether the patterns observed in these species reflects those found in more resilient species. Here, we use microsatellite markers and two Lagrangian models with differing resolutions, to investigate population structure in a stress-tolerant coral survivor Cyphastrea microphthalma, Family Merulinidae, along the north-western Australian coastline. We found evidence of four genetic clusters with some level of admixture among them. However, while there was evidence of population structure within the intensively sampled Pilbara region, the patterns of connectivity differed to those reported previously. WA populations of C. microphthalma were also characterised by lower levels of genetic diversity at higher latitudes. High- and moderate-resolution Lagrangian models did not significantly predict regional-scale genetic connectivity across the Pilbara and Ningaloo (500 km). Although the high-resolution model explained an order of magnitude more genetic variation, suggesting model resolution and resolving coastal processes are important. Over broad spatial scales (nearly 2000 km), all moderate-resolution model particle release durations significantly predicted the genetic differentiation, although over-water distance best-predicted the genetic distance across this spatial scale. This study improves the understanding of connectivity in this region by focusing on a stress-tolerant species incorporating a spatially more intensive sampling effort than previous coral studies. It also shows that further development of Lagrangian models is required, such as inclusion of multi-generational stepwise models and larval behaviour, to improve predictions of connectivity for this coral species in this region.

This study has employed an integrated statistical approach to determine the extents to which species richness and abundance (catch rate) of fishes over reefs along an extensive coastline were related to various factors. Fish were thus sampled by trapping over deep (~ 22 m) and shallow (~ 12 m) reefs along the ~ 1500 km tropical coast of north-western Australia (NWA). Fish were caught during day and night in both dry and wet seasons at two well-spaced locations in each of the Kimberley (13–16°S), Canning (16–19°S) and Pilbara (20–22°S) bioregions. Species richness and abundance were both typically less at the two locations at the lowest latitude than at the two at the highest latitudes. This trend, which contrasts with the paradigm regarding latitudinal trends for these biotic variables, is attributable to the far more extreme hydrological conditions in the Kimberley than Pilbara. Indeed, both biotic variables peaked in the Canning, presumably reflecting, inter alia, the better development of reef and suspension feeder habitats in that bioregion. The peak in abundance was attributable to particularly high numbers of the NWA endemic Lethrinus punctulatus. A greater species richness and abundance of fishes in deeper than shallow water during the wet season, and particularly in areas of greater cyclonic activity, reflect the movement of species such as Lethrinus laticaudis and Lutjanus carponotatus from shallow to calmer, deeper waters. These two biotic variables were greater during the day than night, with a greater number and abundance of diurnally-active species, e.g. lethrinids, feeding overall in the traps than is the case with nocturnal species, e.g. lutjanids. The results imply that the typical poleward latitudinal gradients in species richness and abundance are over-ridden along the NWA coast by environmental differences among bioregions.

As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black-spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localized declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine- and broad-scale population connectivity. This study examined the population structure of P. diacanthus across north-western Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad-scale regions, suggesting fine-scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100 s of km) to account for the restricted exchange among populations (stocks) and to prevent localized extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure.

Dredging can have significant impacts on aquatic environments, but the direct effects on fish have not been critically evaluated. Here, a meta-analysis following a conservative approach is used to understand how dredging-related stressors, including suspended sediment, contaminated sediment, hydraulic entrainment and underwater noise, directly influence the effect size and the response elicited in fish across all aquatic ecosystems and all life-history stages. This is followed by an in-depth review summarizing the effects of each dredging-related stressor on fish. Across all dredging-related stressors, studies that reported fish mortality had significantly higher effect sizes than those that describe physiological responses, although indicators of dredge impacts should endeavour to detect effects before excessive mortality occurs. Studies examining the effects of contaminated sediment also had significantly higher effect sizes than studies on clean sediment alone or noise, suggesting additive or synergistic impacts from dredging-related stressors. The early life stages such as eggs and larvae were most likely to suffer lethal impacts, while behavioural effects were more likely to occur in adult catadromous fishes. Both suspended sediment concentration and duration of exposure greatly influenced the type of fish response observed, with both higher concentrations and longer exposure durations associated with fish mortality. The review highlights the need for in situ studies on the effects of dredging on fish which consider the interactive effects of multiple dredging-related stressors and their impact on sensitive species of ecological and fisheries value. This information will improve the management of dredging projects and ultimately minimize their impacts on fish.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Fishing has had a profound impact on global reef shark populations, and the absence or presence of sharks is strongly correlated with national socio-economic conditions and reef governance. Decades of overexploitation have devastated shark populations, leaving considerable doubt as to their ecological status(1,2). Yet much of what is known about sharks has been inferred from catch records in industrial fisheries, whereas far less information is available about sharks that live in coastal habitats(3). Here we address this knowledge gap using data from more than 15,000 standardized baited remote underwater video stations that were deployed on 371 reefs in 58 nations to estimate the conservation status of reef sharks globally. Our results reveal the profound impact that fishing has had on reef shark populations: we observed no sharks on almost 20% of the surveyed reefs. Reef sharks were almost completely absent from reefs in several nations, and shark depletion was strongly related to socio-economic conditions such as the size and proximity of the nearest market, poor governance and the density of the human population. However, opportunities for the conservation of reef sharks remain: shark sanctuaries, closed areas, catch limits and an absence of gillnets and longlines were associated with a substantially higher relative abundance of reef sharks. These results reveal several policy pathways for the restoration and management of reef shark populations, from direct top-down management of fishing to indirect improvement of governance conditions. Reef shark populations will only have a high chance of recovery by engaging key socio-economic aspects of tropical fisheries.

Many marine fish populations have declined due to the individual or cumulative impacts of increasing water temperatures, ocean acidification, overfishing and other human-induced impacts such as land run-off, dredging and habitat alteration. Some solutions may be offered by ecosystem-based fisheries and conservation management. However, understanding their effectiveness relies on the availability of good quality data on the size distributions and abundance of fish populations and assemblages, collected at appropriate temporal and spatial scales. Since the early 2000s, baited remote underwater video systems (BRUVs) have become a popular tool for collecting data on fish assemblages across a range of depths and habitats. In Australia, this technique has been adopted by many different agencies and institutions, creating a unique opportunity to compile a continental-scale synthesis of fish data using a standardised sampling technique. Key Australian researchers and managers were invited to contribute to a synthesis workshop on baited underwater video in Albany, Western Australia between the 4th and 8th of February 2018. Data from 19,939 BRUVs deployments, collected between 2000 and 2017 around Australia, were compiled using GlobalArchive (globalarchive.org). The workshop identified and prioritised several key research themes that would contribute to the conservation and sustainable management of focal species and broad assemblages. Our goal is to describe where and when the data were collected, the type of equipment used and how the imagery was analysed. We also discuss the types of questions that can be addressed by analysing these standardised datasets and the potential benefits to conservation and fisheries management.

Knowledge of the factors that influence spatial patterns in fish abundance, distribution and diversity are essential for informing fisheries and conservation management. The present study was conducted in the nearshore Pilbara bioregion of north-western Australia where the dynamic marine environment is characterised by large embayments, numerous islands and islets, coexisting with globally significant petrochemical and mineral industries. Within Western Australia, this nearshore bioregion has high biodiversity and is considered to play an essential role in the recruitment of species of commercial importance. To better inform future investigations into both ecological processes and planning scenarios for management, a rapid assessment of the distribution, abundance and associations with nearshore habitats of fishes across the region was conducted. Baited remote underwater stereo-video systems (stereo-BRUVs) were used to simultaneously sample the fish assemblage and habitat composition. Generalised additive mixed models (GAMMs) were used to determine whether the abundance of fishes were related to habitat and a range of environmental variables (visibility, depth, distance to 30 m and 200 m depth isobars, boat ramps and the nearest large embayment (Exmouth Gulf). A diverse fish assemblage comprising 343 species from 58 families was recorded. The abundance and distribution patterns of fishery-target species and of the five most common and abundant species and families were linked positively with areas of high relief, hard coral cover, reef and macroalgae and negatively with the distance to the nearest oceanic waters (200 m depth isobar). This study provides information that can contribute to future marine spatial planning scenarios for management of the Pilbara using a unique, analytical approach that has broad application in biogeography.

Monitoring programs that aim to measure the diversity, abundance and biomass of fishes depend on accurate and reliable biological data to guide the development of robust management plans. It is important to implement an appropriate sampling technique that provides a comprehensive assessment, while reducing associated biases in the data collection process. We compared the sampling abilities of four different underwater stereo-video techniques; baited remote underwater stereo-video systems (BRUV), diver operated stereo-video (DOV), and two relatively new methodologies; slow towed stereo-video (STV) and remotely operated vehicle (ROV) fitted with a stereo-video. Comparisons were conducted in a temperate reef system along a single limestone ridge within Geographe Bay, Western Australia. More fish species and individuals were sampled by BRUVs, while transect based methods (DOV, STV, and ROV) were comparable. Combining BRUVs with a transect method resulted in a ~10% increase in observed diversity. BRUVs had a higher statistical power to detect change in comparison to the transect methods. This was due to the higher variability observed in transect methods that may sample greater habitat heterogeneity within a sample unit compared to BRUVs. Although differences did exist, data collected with the ROV was generally comparable to the other transect methods. We believe further research into ROV use is warranted as they provide a safer alternative to diver-based techniques and have the ability to extend into deeper-waters. We recommend that for fish diversity and abundance assessments a sampling strategy that combines BRUVs and a transect method should be adopted.

The distribution, abundance and composition of marine fish assemblages are influenced by changes in behaviour and movement associated with the diel cycle. The majority of studies exploring day–night differences have demonstrated that there is a greater abundance and diversity of fishes during diurnal compared with nocturnal hours, and that fish assemblage composition varies with time of day or night. We investigated fine-scale (hourly) diel cycles in the composition and relative abundance of temperate reef fishes using unbaited remote underwater video systems. We observed short crepuscular changeover periods with the hours around dawn and dusk sharing many species, some of which are nocturnal and others diurnal. Diurnal surveys recorded a greater number of individuals (16,990) and species (70) than nocturnal surveys (1053 individuals and 19 species). There was a clear difference between the diurnal assemblage, which was characterized by benthic invertivores, and the nocturnal assemblage composition, which contained zooplanktivores and generalist feeders. Within the diurnal period the hourly temporal variation was relatively homogenous, indicating that standardization of diurnal sampling to a particular time of day may not be necessary.

In this study, a total of 212 eggs were visually identified as snapper Chrysophrys auratus. Real-time PCR confirmed visual identification in 69% of cases but corroboration varied widely among plankton samples. The use of molecular tools to support visual identification prior to adopting daily egg production stock assessment methods should be considered.

Understanding the drivers of dispersal among populations is a central topic in marine ecology and fundamental for spatially explicit management of marine resources. The extensive coast of Northwestern Australia provides an emerging frontier for implementing new genomic tools to comparatively identify patterns of dispersal across diverse and extreme environmental conditions. Here, we focused on the stripey snapper (Lutjanus carponotatus), which is important to recreational, charter-based and customary fishers throughout the Indo-West Pacific. We collected 1,016 L. carponotatus samples at 51 locations in the coastal waters of Northwestern Australia ranging from the Northern Territory to Shark Bay and adopted a genotype-by-sequencing approach to test whether realized connectivity (via larval dispersal) was related to extreme gradients in coastal hydrodynamics. Hydrodynamic simulations using CONNIE and a more detailed treatment in the Kimberley Bioregion provided null models for comparison. Based on 4,402 polymorphic single nucleotide polymorphism loci shared across all individuals, we demonstrated significant genetic subdivision between the Shark Bay Bioregion in the south and all locations within the remaining, more northern bioregions. More importantly, we identified a zone of admixture spanning a distance of 180 km at the border of the Kimberley and Canning bioregions, including the Buccaneer Archipelago and adjacent waters, which collectively experiences the largest tropical tidal range and some of the fastest tidal currents in the world. Further testing of the generality of this admixture zone in other shallow water species across broader geographic ranges will be critical for our understanding of the population dynamics and genetic structure of marine taxa in our tropical oceans.

Marine macroinvertebrates support important fisheries throughout the Indo-Pacific, but stocks of species such as trochus (Rochia nilotica) are easily overharvested. In north-western Australia, trochus are taken from inshore reefs by Indigenous Australians and oceanic reefs by artisanal Indonesian fishers. The management of these environmentally distinct regions relies on understanding their spatial interdependencies, yet connectivity between them has not been evaluated empirically. Here, we used genotype-by-sequencing analysis of 514 trochus samples collected from 17 locations (15 in the inshore Kimberley, 2 offshore oceanic sites). Analysis of 5428 polymorphic single nucleotide polymorphism loci revealed significant genetic subdivision between the oceanic and coastal sites, and a subset of loci exhibited significantly higher subdivision, suggesting they are subject to directional selection. Population differentiation was also evident between the two oceanic sites, but not between coastal sites. Trochus populations from the coastal Kimberley and oceanic reefs represent two genetically and demographically independent units, with preliminary evidence for local adaptation to these distinctive environments. Management strategies for R. nilotica reflect these divisions, but the limited connectivity among oceanic populations indicates that they are vulnerable to overexploitation. Furthermore, their potential adaptive distinctiveness indicates that coastal stocks may be unsuitable for replenishing oceanic stocks.

As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black‐spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localized declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine‐ and broad‐scale population connectivity. This study examined the population structure of P. diacanthus across north‐western Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad‐scale regions, suggesting fine‐scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100 s of km) to account for the restricted exchange among populations (stocks) and to prevent localized extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure.

We utilized a spatial and temporal analyses of genetic structure, supplemented with ecological and oceanographic analysis, to assess patterns of population connectivity in a coral reef fish Chromis margaritifer among the unique and remote atolls in the eastern Indian Ocean. A subtle, but significant genetic discontinuity at 10 microsatellite DNA loci was detected between atoll systems corresponding with a low (≤ 1%) probability of advection across the hundreds of kilometers of open ocean that separates them. Thus, although genetic connections between systems are likely maintained by occasional long-distance dispersal of C. margaritifer larvae, ecological population connectivity at this spatial scale appears to be restricted. Further, within one of these atoll systems, significant spatial differentiation among samples was accompanied by a lack of temporal pairwise differentiation between recruit and adult samples, indicating that restrictions to connectivity also occur at a local scale (tens of kilometers). In contrast, a signal of panmixia was detected at the other atoll system studied. Lastly, greater relatedness and reduced genetic diversity within recruit samples was associated with relatively large differences among them, indicating the presence of sweepstakes reproduction whereby a small proportion of adults contributes to recruitment in the next generation. These results are congruent with earlier work on hard corals, suggesting that local production of larvae drives population replenishment in these atoll systems for a range of coral reef species.

Large-scale studies are required to elucidate the environmental factors that structure faunal communities. The relationships between the characteristics of the coastal ichthyofaunas over the soft substrata of tropical north-western Australia and both latitude and environmental factors were thus explored by analysing trawl data obtained for deep and shallow inshore waters at 7 regularly spaced locations along this 1500 km coast during both the dry and wet seasons. In the dry season, species richness and density were greater in the Kimberley and Pilbara bioregions than in the intervening Canning bioregion, where, in contrast to particularly the Kimberley, rivers and mangroves are largely absent. Species richness and density were greatest in the most northern bioregion (Kimberley) during the wet season, when nutrient input from rivers and water temperatures were highest. The high species richness and density at 1 Canning location during the wet season was presumably related to increased productivity brought about by local cyclonic events. Ichthyofaunal compositions in the Kimberley differed markedly from those in the Canning and Pilbara, where tidal range was less and water clarity greater due, in particular, to far greater densities of leiognathids and terapontids. Compositions at all locations in the dry season differed from those in the wet, when chlorophyll a concentrations and/or water temperatures were greatest and large numbers of certain species were recruited. Ichthyofaunal composition at each location almost invariably differed markedly between water depths, reflecting, inter alia, the tendency for some species to use nearshore waters as nursery areas and for others to occupy particular habitats.

Lutjanus carponotatus ranges from the Indian Ocean to northern Australia and Papua New Guinea and is an important species for both commercial and recreational fisheries. Due to its life history characteristics and fishing pressures, L. carponotatus is vulnerable to overfishing and suitable management is essential. This phylogenetic and population genetic study assessed the population genetic structure of L. carponotatus at seven locations in three bioregions in Western Australia (WA) using the mitochondrial DNA control region. Analysis of molecular variance (AMOVA) indicated no genetic differentiation among locations within (oCT = 0.051) and among bioregions (oSC = −0.026). Phylogenetic analyses indicated no geographic partitioning within WA, though two distinct lineages were found. Within these two lineages there was no significant spatial partitioning, suggesting a panmictic population that can, under current conditions, be managed as a single stock. WA and Great Barrier Reef (GBR) population genetic data were then combined to determine the broad-scale connectivity between the east and west coast of Australia. L. carponotatus from the GBR did differ significantly (FST = 0.64, p = < 0.001) from the WA population, indicating the two populations do not exchange any migrants and should be managed as discrete stocks. As an indicator of population resilience, genetic variability was compared among WA and GBR populations of L. carponotatus and we show that the WA population has almost three times the genetic variability of the GBR population, suggesting that it will be better able to adapt to environmental change expected during the 21st century.

Accelerating coastal development and shipping activities dictate that dredging operations will intensify, increasing potential impacts to fishes. Coastal fishes have high economic, ecological, and conservation significance and there is a need for evidence-based, quantitative guidelines on how to mitigate the impacts of dredging activities. We assess the potential risk from dredging to coastal fish and fisheries on a global scale. We then develop quantitative guidelines for two management strategies: threshold reference values and seasonal restrictions. Globally, threatened species and nearshore fisheries occur within close proximity to ports. We find that maintaining suspended sediment concentrations below 44 mg/L (15–121 bootstrapped CI) and for less than 24 hours would protect 95% of fishes from dredging-induced mortality. Implementation of seasonal restrictions during peak periods of reproduction and recruitment could further protect species from dredging impacts. This study details the first evidence-based defensible approach to minimize impacts to coastal fishes from dredging activities.

Aim To test the following hypotheses regarding ichthyofaunal compositions along an extensive tropical coastline. The compositions over soft substrates and reefs: (1) consistently differ markedly; (2) change progressively with latitude and temperature through sequential changes in the abundances of certain species; and (3) vary among bioregions, as those regions differ markedly in their environmental characteristics. Location Tropical north-western Australia. Methods Similarity matrices, derived from percentage contributions of each fish species to catches obtained over soft substrates by trawling and over reefs by trapping at seven regularly spaced sites along 1500 km of coast, were subjected to cluster analysis, non-metric multidimensional scaling ordination and associated tests. Results In total, 361 species were obtained by trawling and trapping along the tropical coast of north-western Australia (NWA). Only 56 species were recorded over both soft substrates and reefs, whereas 229 and 76 species were caught exclusively over soft substrates and reefs, respectively. The Leiognathidae, Carangidae and Terapontidae contributed most individuals (62.2%) to catches over soft substrates, whereas the Lethrinidae and Lutjanidae dominated those over reefs (81.9%). The species compositions in both habitats were related to latitude and water temperature. Ichthyofaunal compositions in the Kimberley region differed markedly from those in the Canning/Pilbara regions further south, which, in turn, each had distinct characters. The vast majority of species found over both habitats also occur in the Pacific Ocean to the north. Main conclusions The most important fish families over soft substrates and reefs in inshore marine waters of tropical NWA differ markedly. The ichthyofaunal compositions of both habitats undergo similar patterns of progressive change with latitude, due to site-staggered changes in the relative abundances of key fish species in their respective habitats. Ichthyofaunal composition in both habitats was found to be influenced by water temperature. The latitudinal trends exhibited by species composition are overlaid on a strong bioregional effect, reflecting the influence of the very different environmental conditions in those bioregions, which include marked differences in such factors as tidal regime, turbidity and whether mangroves are nearby. The important contribution of species with a Pacific affinity was presumably facilitated by the polewards-flowing Indonesian Throughflow, which links the Pacific Ocean with waters bordering the NWA coast.

Trap sampling over reefs in deep (mean = 20 m) and shallow (mean = 10 m) waters along c. 1500 km of coastline in tropical north-western Australia during both day and night and in wet and dry periods yielded 23 377 fishes, representing 32 families, 58 genera and 119 species. Individuals of the Serranidae, Lutjanidae, Lethrinidae and Carangidae contributed 88.9% to the total catch. The ichthyofaunal compositions of the Kimberley, Canning and Pilbara bioregions were relatively discrete. Species composition was influenced far more by location (latitude) than by water depth, period and time of day, and underwent a gradational change southwards. The latter change reflected differences in the trends exhibited by the relative abundances of certain species with increasing latitude and the confinement of other species largely to particular regions. The three most abundant species, i.e. Lethrinus sp. 3, Lutjanus carponotatus and Lethrinus laticaudis contributed 34.8, 20.8 and 11.6% to the total catch, respectively. The first species was rarely recorded in the two most northern locations and was abundant in the four most southern locations, whereas the last two species were relatively more abundant in northern than in southern locations. Lutjanus bitaeniatus and Lutjanus johnii were found exclusively at the two locations in the Kimberley region, whereas Abalistes stellatus, Pentapodus emeryii and Lethrinus nebulosus were not caught in this region but were found in both locations of the Canning and Pilbara regions. The species composition in deep and shallow waters at each location almost invariably differed significantly between day and night and between dry and wet periods, with species such as L. bitaeniatus, L. johnii, Lutjanus sebae and A. stellatus being more abundant over deep reefs, whereas L. carponotatus, L. laticaudis, Siganus fuscescens and Lethrinus lentjan were more numerous over shallow reefs. Species such as L. johnii and Lethrinus atkinsoni were relatively more important in night-time than daytime catches, whereas the reverse applied to Lethrinus lentjan, L. laticaudis and Choerodon cyanodus. Lethrinus sp. 3 and L. laticaudis were relatively more important in catches during the dry than wet period.

The grass emperor Lethrinus laticaudis is a conspicuous element of the commercial and recreational catch from nearshore reef systems across northern Australia. The nearshore reef systems across northern Australia are exposed to increasing levels of fishing pressure from commercial and recreational fishers. To inform ongoing management of this species, the present study examined the stock structure of L. laticaudis across northern Australia using a combination of complementary techniques. In all, 342 L. laticaudis samples were collected from 13 locations in the coastal waters of northern Australia ranging from the Pilbara region of Western Australia to Moreton Bay in south-east Queensland. Population genetic analyses using microsatellite markers demonstrated that there were at least four genetically distinct populations across northern Australia with gene flow between management jurisdictions (with significantly more separation between Western Australian and Northern Territory locations than between Northern Territory and Queensland locations). An isolation by distance effect was evident (genetic differences increasing linearly with distance). Otolith microchemistry and parasitology analyses indicated some spatial structuring of populations within broader regions. These findings of restricted connectivity at small spatial scales suggest that L. laticaudis is vulnerable to localised depletion in areas where fishing effort is concentrated. This conclusion is consistent with recent observations of fishery declines in heavily fished locations.

Mean number of species and density of fishes in nearshore shallow waters of Shark Bay, a large subtropical embayment, were c. seven and 19.5 times greater in seagrass than over bare sand, where protection from predators and the abundance of potential invertebrate prey were less. The number of fish species and density of fishes over bare sand were lower in nearshore than offshore waters, where there was a greater amount of organic material and thus presumably a greater density of benthic macroinvertebrate prey. Species composition in vegetated and unvegetated habitats differed markedly, with species such as Monacanthus chinensis, Apogon rueppellii and Pelates quadrilineatus being largely confined to seagrass, whereas others such as Pseudorhombus jenynsii, Torquigener whitleyi and Engyprosopon grandisquama were found predominantly or exclusively over bare sand. The ichthyofauna in beds of Posidonia australis, in which the canopy is uniformly dense, differed in composition and comprised a greater number of species and density of fishes than that in Amphibolis antarctica, in which an open space is present beneath the terminal clusters of relatively short leaves. Species composition in the beds of both of these seagrass species underwent well defined cyclical changes, caused by out-of-phase sequential changes in the densities of certain species. Such changes were less common over bare sand, where the ichthyofaunal composition was more variable. The number of species and density of fishes over bare sand were greater at night than during the day, reflecting, in part, a tendency for species such as A. rueppellii to move into unvegetated areas to feed at night, when the likelihood of predation by visual predators would be reduced. Within Shark Bay, ichthyofaunal composition is influenced most by habitat type (vegetated v. unvegetated), followed in general by water depth and then region in the bay and time of year.

The UV absorption spectra of B(N3)3, BCl(N3)2 and BCl2N3 isolated in low temperature argon matrices were measured as the matrices were photolyzed with the loosely focused output of a D2 lamp. IR spectra were taken simultaneously with the UV spectra, and changes in the UV spectra were correlated with changes in the IR spectra. A series of bands at 348.0, 353.5, 360.0, 366.0, 372.5, and 379.5 nm appeared during the photolysis of B(N3)3 and were assigned as a vibrational progression in a bending mode of NNBN. Photolysis of BCl(N3)2 generated a feature at 408 nm that displayed evidence of vibrational structure and a sharp band at 275 nm. The 408 nm absorption was tentatively assigned to ClBN2, a three-membered ring compound, and the 275 nm band as the A1Π ← X1Σ transition in BCl. No new UV features were observed during the photolysis of BCl2N3, although the IR spectrum clearly indicated the formation of ClBNCl. These data indicate that ClBNCl has no UV absorption spectrum at wavelengths longer than 240 nm.

BCl(N3)2 was isolated in a low-temperature argon matrix and its FTIR spectrum measured. The splitting due to the natural abundances of 10B and 11B and ab initio calculations of the ground-state fre...

We have observed the negative ion photoelectron spectrum of the methylnitrene ion, CH3N−, and measured the electron affinity of methylnitrene, EA(CH3N)=0.022±0.009 eV. In addition to detaching the methylnitrene anion to the ground state of CH3N(X 3A2), we also detect the first electronically excited state of methylnitrene, a 1E. We measure the singlet/triplet splitting to be ΔE(a 1E−X 3A2)=1.352±0.011 eV. The photoelectron spectrum of CH3N a 1E contains relatively sharp vibronic structure. Unlike the spectra from H2CC−, the photoelectron spectra for CH3N− show no evidence for a barrier separating the rearrangement of singlet methylnitrene to methyleneimine, 1[CH3N] → CH2=NH.

We utilized a spatial and temporal analyses of genetic structure, supplemented with ecological and oceanographic analysis, to assess patterns of population connectivity in a coral reef fish Chromis margaritifer among the unique and remote atolls in the eastern Indian Ocean. A subtle, but significant genetic discontinuity at 10 microsatellite DNA loci was detected between atoll systems corresponding with a low (≤ 1%) probability of advection across the hundreds of kilometers of open ocean that separates them. Thus, although genetic connections between systems are likely maintained by occasional long-distance dispersal of C. margaritifer larvae, ecological population connectivity at this spatial scale appears to be restricted. Further, within one of these atoll systems, significant spatial differentiation among samples was accompanied by a lack of temporal pairwise differentiation between recruit and adult samples, indicating that restrictions to connectivity also occur at a local scale (tens of kilometers). In contrast, a signal of panmixia was detected at the other atoll system studied. Lastly, greater relatedness and reduced genetic diversity within recruit samples was associated with relatively large differences among them, indicating the presence of sweepstakes reproduction whereby a small proportion of adults contributes to recruitment in the next generation. These results are congruent with earlier work on hard corals, suggesting that local production of larvae drives population replenishment in these atoll systems for a range of coral reef species.

The tandem flowing afterglow-selected ion flow tube has been employed to measure the gas-phase acidities of a family of deuterated ethanols. We find that both α and β deuterated ethanols are weaker acids than undeuterated ethanol with α deuteration having a more pronounced effect. The acidities, relative to undeuterated ethanol [ΔHacid,298 K (CH3CH2OH) = 377.5 ± 2kcal mol−1] are ΔΔHacid(CD3CH2OH) = 0.20 ± 0.15kcal mol−1, ΔΔHacid(CH3CD2OH) = 0.35 ± 0.15 kcal mol−1, and ΔΔHacid0(CD3CD2OH) = 0.50 ± 0.15 kcal mol−1. In a separate set of measurements, we have studied the negative ion photoelectron spectroscopy of a set of ethoxide ions to determine the electron affinities of the corresponding ethoxy radicals. The electron affinities decrease with increasing deuterium substitution. We find: EA(CH3CH2O) = 39.55 ± 0.16kcal mol−1, EA(CH3CD2O) = 39.48 ± 0.16kcal mol−1, EA(CD3CH2O) = 39.41 ± 0.16kcal mol−1, and EA(CD3CD2O) = 39.27 ± 0.16 kcal mol−1; the relative error bars are ±0.05 kcal mol−1. The corresponding O-H bond strengths of the deuterated ethanols can be extracted from these acidities and electron affinities. We find that α deuteration increases the OH bond strength by 0.3 ± 0.2 kcal mol−1 while β deuteration has a negligible effect. The bond dissociation energies, relative to undeuterated ethanol [D0,OK (CH3CH2OH) = 102.2kcal mol−1] are D0,OK(CD3CH2OH) = 102.3 ±0.2kcal mol−1, D0,OK(CH3CD2OH) = 102.5 ± 0.2kcal mol−1, and D0,OK(CD3CD2OH) = 102.5 ± 0.2kcal mol−1. Indicated error bars are relative errors; absolute errors are ±2 kcal mol−1. Hartree-Fock-SCF calculations were performed on the various deuterated and undeuterated ethanols, ethoxy radicals, and ethoxide anions to calculate the relative acidities, electron affinities and bond dissociation energies. The results are in good agreement with our experimental values.

BCl(N3)2 was isolated in a low-temperature argon matrix and its FTIR spectrum measured. The splitting due to the natural abundances of 10B and 11B and ab initio calculations of the ground-state fre...

We have measured the negative ion photoelectron spectra of CH2N− and CD2N− and find the electron affinities: EA(CH2N)=0.511±0.008 eV and EA(CD2N)=0.498±0.011 eV. Franck–Condon simulations of these spectra are carried out and we estimate the CH2N− and CH2N geometry differences; we fit our spectra with the following [constrained] molecular structures. We combine our EA(CH2N) with the results of previous gas phase ion studies to extract a number of thermochemical parameters (kcal/mol): Do0(CH2N–H)=85±5, Do0(H–HCN)=23±6, Do0(H2C–N)=144±6, and the isomerization enthalpy of H2CN+→HCNH+ is ΔHisom(C2v→C∞v)=−51±7. Attempts to calculate the geometry and vibrational frequencies of the H2CN radical are disappointing. Unrestricted Hartree–Fock and second‐order Mo/ller–Plesset ab initio calculations in a 6‐31++G** basis produce badly spin‐contaminated wave functions which do not reproduce the experimental findings.

Due to human activities, marine and terrestrial ecosystems face a future where disturbances are predicted to occur at a frequency and severity unprecedented in the recent past. Of particular concern is the ability of systems to recover where multiple stressors act simultaneously. We examine this issue in the context of a coral reef ecosystem where increases in stressors, such as fisheries, benthic degradation, cyclones and coral bleaching, are occurring at global scales. By utilizing long-term (decadal) monitoring programs, we examined the combined effects of chronic (removal of sharks) and pulse (cyclones, bleaching) disturbances on the trophic structure of coral reef fishes at two isolated atoll systems off the coast of northwest Australia. We provide evidence consistent with the hypothesis that the loss of sharks can have an impact that propagates down the food chain, potentially contributing to mesopredator release and altering the numbers of primary consumers. Simultaneously, we show how the effects of bottom-up processes of bleaching and cyclones appear to propagate up the food chain through herbivores, planktivores and corallivores, but do not affect carnivores. Because their presence may promote the abundance of herbivores, the removal of sharks by fishing has implications for both natural and anthropogenic disturbances involving the loss of corals, as herbivores are critical to the progress and outcome of coral recovery.

We have re-examined the photoelectron spectra of O 2 − and NO − using negative ion photoelectron spectroscopy. We observe detachment to three electronic states ( 3 Σ g − , 1 Δ g , 1 Σ g + ) of O 2 and to one electronic state ( 2 Π) of NO. We find the following electron affinities: EA (O 2 )=0.451±0.007 eV and EA(NO)=0.026±0.005 eV. Analyses of the photoelectron spectra yield a value for the fundamental frequency of O 2 − (1073±50 cm −1 ) while the bond lengths are r e (O 2 − =1.347±0.005 A and r e (NO − = 1.271±0.005 A.