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The abundance and distribution of demersal fishes rely on larvae successfully settling from the pelagic environment to a benthic habitat and their subsequent survival. With high mortality rates during this life stage, settling to a habitat that maximizes survival is critical. However, relationships between settlement choices and subsequent survival are poorly understood and may vary among species with different habitat preferences. To test this, we focused on five congeneric (Pomacentrus) damselfish species that are known to differ in their habitat choices and explored whether habitat associations at settlement influenced survival. Newly settled individuals were tagged and monitored daily for two weeks to estimate natural mortality rates. Morphological attributes of fish and characteristics of settlement habitats, including depth, rugosity, benthic substrata, and local fish assemblages, were used to predict mortality. We found that some species displayed stronger associations with specific benthic substrata at settlement, but contrary to expectations, these selected habitat characteristics were relatively weak predictors of survivorship. Our survival analysis revealed that the best predictors of survivorship were rugosity (P. adelus and P. amboinensis) and two morphological traits, body depth and ocellus size (P. chrysurus and P. adelus). Interestingly, we found that P. moluccensis that settled in areas of high coverage of mounding coral experienced increased mortality. Of the remaining substrata, analysis showed that instead of associating with habitat characteristics enhancing survivorship, individuals tended not to associate with habitats characteristics that increased mortality (e.g., Turbinaria and sand). This study highlights the species-specific drivers of early post-settlement mortality in coral reef fishes. [ABSTRACT FROM AUTHOR]

Hydrodynamic processes are important in all marine environments and on coral reefs drive patterns of habitat zonation, community structure, and biodiversity. Abrupt geomorphological features like pinnacles and seamounts often possess distinct localized currents and these habitats are also often characterized by high abundance and biomass of fishes. However, differences in fish community structure between pinnacles and emergent reefs, and their key drivers are poorly understood. In this study, we compared fish communities among emergent fringing and offshore coral reefs, and submerged pinnacle reefs in Papua New Guinea. Submerged pinnacles possessed higher fish biomass, abundance, and species richness than both fringing and offshore emergent reefs. We collected in‐situ current speed and temperature data over a full year at each reef and used random forest analysis to investigate the relative influence of hydrodynamics compared to other well‐established drivers of reef fish biodiversity, including habitat and biogeographic factors. Environmental variables explained 70%, 52%, and 5% of variability in models for species richness, abundance and biomass respectively. In all models, average current speed, current speed variability, and reef area were consistently among the most influential variables. Models examining relationships between fish biodiversity metrics and current speed did not yield conclusive results but did highlight the association of distinct hydrodynamic regimes on pinnacles with high fish richness, abundance, and biomass. Our study highlights the strong influence of reef‐scale hydrodynamics on fish biodiversity and demonstrates the ecological value of small, submerged coral reefs, which are globally numerous yet remain understudied in coral reef ecology. [ABSTRACT FROM AUTHOR]

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Body size influences many life‐history traits, with small‐bodied animals tending to have short life spans, high mortality and greater reproductive effort early in life. In this study, the authors investigated the life‐history traits and reproductive strategies of three small‐bodied coral reef gobies of the genus Trimma: Trimma benjamini, Trimma capostriatum and Trimma yanoi. The authors found all Trimma species studied attained a small body size of <25 mm, had a short life span of <140 days and experienced high estimated daily mortality of 3.0%–6.7%. Furthermore, the pelagic larval phase accounted for 25.3%–28.5% of the maximum life span, and maturation occurred between 74.1 and 82.1 days at 15.2–15.8 mm, leaving only 35%–43% of the total life span as a reproductively viable adult. All mature individuals had gonad structures consistent with bidirectional sex change, with bisexual gonads including both ovarian and testicular portions separated by a thin wall of connective tissue. In the female and male phases, only ovaries or testes were mature, whereas gonadal tissue of the non‐active sex remained. One T. benjamini individual and one T. yanoi individual had ovarian and testicular tissue active simultaneously. The results of this study highlight the life‐history challenges small CRFs face on their path to reproduction and reproductive strategies that could be beneficial in fishes with high and unpredictable mortality and short reproductive life spans. [ABSTRACT FROM AUTHOR]

Hydrodynamics on coral reefs vary with depth, reef morphology and seascape position. Differences in hydrodynamic regimes strongly influence the structure and function of coral reef ecosystems. Submerged coral reefs on steep-sided, conical bathymetric features like seamounts experience enhanced water circulation as a result of interactions between currents and the abrupt physical structure. There may also be similar interactions between smaller pinnacles and regional water currents in offshore locations (crests > 10 m), while shallow reefs (crests <10 m) may be more subject to surface currents driven by wind, waves and tide. Here we tested whether coral pinnacles experienced stronger and more variable currents compared to emergent reefs at the same depth in both nearshore and offshore positions. Current speeds and temperature were monitored for 12 months at 11 reefs, representing the three different reef categories: submerged offshore pinnacles, emergent offshore reefs and emergent nearshore reefs. We found different patterns in current speeds and temperature among reef types throughout the year and between seasons. Submerged pinnacles exhibited stronger, more variable current speeds compared to both near and offshore emergent reefs. We found seasonal changes in current speeds for pinnacle and nearshore reefs but no variation in current strength on offshore reefs. Whilst instantaneous current directions did reflect the seascape position of individual sites, there was no difference in the directional variability of current speeds between reef types. Annual daily average temperatures at all reef types were not strongly seasonal, changing by less than 2 °C throughout the year. Daily temperature ranges at specific sites however, exhibited considerable variability (annual range of up to 6.5 °C), particularly amongst offshore emergent reefs which experienced the highest temperatures despite greater exposure to regional-scale circulation patterns. Additionally, we found a consistent mismatch between satellite sea surface temperatures and in-situ temperature data, which was on average 2 °C cooler throughout the annual study period. Our results suggest that distinct hydrodynamic processes occur on smaller submerged structures that are physically analogous to seamounts. Our findings highlight important nuances in environmental processes that occur on morphologically distinct coral reef habitats and these are likely to be important drivers for the community dynamics of organisms that inhabit these reefs. [ABSTRACT FROM AUTHOR]

Sponges (Porifera) are a key component of many coral reef ecosystems. In some biogeographic regions, they are considered the dominant benthic fauna and they have the capacity to fulfil many similar roles to reef-building scleractinians. Certainly, sponges predominate at depth, below the critical thresholds of most coral species. The biological and physical attributes of these biogenic communities contribute essential resources for many reef-associated fishes. However, while fish–sponge interactions have been widely documented, there is no global synthesis of the literature on these interrelationships from the perspective of fish ecology. Here we evaluate coral reef fish–sponge relationships, including the role of sponges in providing food and shelter for fishes, the influence fishes have on sponge distribution and abundance and possible outcomes of climate change on fish–sponge interactions. To date, 16 fish families have been shown to associate with 56 different sponge genera, using them as either a source of shelter (n = 17) or a food source (n = 50), although methodologies for the latter currently lack consistency. We demonstrate that a more comprehensive understanding of fish–sponge interactions has been garnered from tropical Atlantic coral reefs, which has resulted in a strong biogeographic bias. While it is evident that in some areas of the Caribbean fish are key in shaping the distribution and abundance of sponges, it is not yet known whether this conclusion applies to the Indo-Pacific. With increasing stresses such as bleaching events impacting coral reef ecosystems, further work is needed to evaluate whether sponges can fulfil similar functional roles to those previously provided by reef-building scleractinians. Similarly, determining whether sponge expansion will compensate for the negative effects of reef degradation, or contribute to their decline, is vital. [ABSTRACT FROM AUTHOR]

Hybridization and introgression are evolutionarily significant phenomena breaking down species boundaries. "Hybrid zones" (regions of species overlap and hybridization) enable quantification of hybridization frequency and examination of mechanisms driving and maintaining gene flow. The hybrid anemonefish Amphiprion leucokranos is found where parent species (A. chrysopterus; A. sandaracinos) distributions overlap. Here, we examine geographic variation in hybridization and introgression, and potential impacts on parent species integrity through assessing relative abundance, social group composition, and genetic structure (mtDNA cytochrome b, 21 microsatellite loci) of taxa at three hybrid zone locations: Kimbe Bay (KB) and Kavieng (KA), Papua New Guinea; the Solomon Islands (SO). Relative abundances of and size disparities between parent species apparently drive hybridization frequency, introgression patterns, and genetic composition of taxa. Conspecific groups are most common in KB (65%) where parent species are similarly abundant. Conversely, mixed species groups dominate SO (82%), where A. chrysopterus is more abundant. Hybrids most commonly cohabit with A. sandaracinos in KB (17%), but with A. chrysopterus in KA (22%) and SO (50%). Genetic differentiation (nDNA) analyses indicate that parent species remain distinct, despite ongoing hybridization and hybrids are genetically similar to A. sandaracinos—resulting from persistent backcrossing with this smallest species. This study shows that hybridization outcomes may depend on the social and ecological context in which taxa hybridize, where relative abundance and disparate size of parent species explain the frequency and patterns of hybridization and introgression in the A. leucokranos hybrid zone, reflecting size‐based dominance behaviors of anemonefish social groups. [ABSTRACT FROM AUTHOR]

Sexual dimorphism is a common in the animal kingdom and is often linked to mate choice or competition for mates in polygynous mating systems. However, sexual dimorphism is less common in species that form heterosexual pairs and has not been recorded in pair-forming coral-reef fish. Here we demonstrate a pronounced morphological difference between males and females in the humphead bannerfish (Heniochus varius)—a pair-forming coral reef butterflyfish. Males of paired individuals collected in Kimbe Bay, Papua New Guinea had substantially larger hump and horn protrusions on their heads than females. Fish were also sexed, sized and aged to determine the reproductive and demographic basis of the pairing behaviour. H. varius pairs were exclusively heterosexual and were assorted strongly by total length and slightly less so by age. Females in pairs were generally the same size as male partners, but were frequently older by a year and sometimes more. Hump and horn lengths increased proportionally to body-size in both sexes, with horns growing at a greater rate among males. These findings suggest that H. varius form pairs primarily for reproductive purposes, with selection via a size-assortative process that likely also extends to selection for larger hump and horn protrusions among males. The larger humps and horns in males appear to be the first recorded example of a secondary sexual morphological characteristic in a pair-forming coral reef fish species. [ABSTRACT FROM AUTHOR]

Acentralissue in evolutionaryecology is how patterns ofdispersal influence patterns of relatedness in populations. In terrestrial organisms, limited dispersal of offspring leads to groups of related individuals. By contrast, for most marine organisms, larval dispersal in open waters is thought to minimize kin associations within populations. However, recent molecular evidence and theoretical approaches have shown that limited dispersal, sibling cohesion and/or differential reproductive success can lead to kin association and elevated relatedness. Here, we tested the hypothesis that limited dispersal explains small-scale patterns of relatedness in the pajama cardinalfish Sphaeramia nematoptera. We used 19 microsatellite markers to assess parentage of 233 juveniles and pairwise relatedness among 527 individuals from 41 groups in Kimbe Bay, Papua New Guinea. Our findings support three predictions of the limited dispersal hypothesis: (i) elevated relatedness within groups, compared with among groups and elevated relatedness within reefs compared with among reefs; (ii) a weak negative correlation of relatedness with distance; (iii) more juveniles than would be expected by chance in the same group and the same reef as their parents. We provide the first example for natal philopatry at the group level causing small-scale patterns of genetic relatedness in a marine fish. [ABSTRACT FROM AUTHOR]

Coral reef fishes are known to respond to chemical cues in the selection of appropriate microhabitats at settlement. Coral- and non-coral-associated species are likely to respond to different stimuli and the cues may change as larvae settle and become familiar with the reef environment. Here, the chemosensory responses of both late-stage larvae and newly settled juvenile damselfishes to microhabitat odours were tested in Kimbe Bay (PNG), including four obligate coral-dwelling species (Dascyllus melanurus, D. reticulatus, Chrysiptera arnazae and Pomacentrus moluccensis) and four rubble-dwelling species (Pomacentrus adelus, P. simsiang, Chrysiptera cyanea and C. rollandi). Damselfishes were subjected to a series of pair-wise chemosensory choice trials using a two-channel choice flume. The responses by late-stage larvae (pre-settled) to chemical cues from their preferred microhabitat type mirrored those exhibited by recently settled juveniles. All four rubble-dwelling damselfish species exhibited a significant aversion toward chemical cues derived from coral microhabitats, preferring to remain either in the water seeded with chemical cues derived from rubble, or the unseeded (control) water. The obligate coral-dwelling damselfish species tended to avoid rubble and select coral cues when tested against seawater, but unexpectedly, exhibited a neutral response when given a choice between coral and rubble odours. These results indicate that coral and rubble-dwelling damselfish differ in the strength of their attraction to preferred or avoidance of non-preferred microhabitats. Both factors are likely to play a role in settlement choices. Our results indicated that for some species, newly settled juveniles could act as suitable substitutes for testing larval behavioural traits. [ABSTRACT FROM AUTHOR]

While there is increasing evidence for habitat specialization in coral reef fishes, the extent to which different corals support different fish communities is not well understood. Here we quantitatively assess the relative importance of different coral species in structuring fish communities and evaluate whether sampling scale and coral colony size affect the perceived strength of fish-habitat relationships. Fish communities present on colonies of eight coral species (Porites cylindrica, Echinopora horrida, Hydnophora rigida, Stylophora pistillata, Seriatopora hystrix, Acropora formosa, A. tenuis and A. millepora) were examined in the Lizard Island lagoon, Great Barrier Reef, Australia. Additionally, the differences in fish communities supported by three coral species (P. cylindrica, E. horrida, H. rigida) were investigated at three spatial scales of sampling (2x2 m, 1x1 m, 0.5x0.5 m). Substantial differences in fish communities were observed across the different coral species, with E. horrida and H. rigida supporting the most fish species and individuals. Coral species explained more of the variability in fish species richness (20.9–53.6%), than in fish abundance (0–15%). Most coral species supported distinctive fish communities, with dissimilarities ranging from 50 to 90%. For three focal coral species, a greater amount of total variation in fish species richness and fish abundance was evident at a larger scale of sampling. Together, these results indicate that the structure of reef fish communities is finely tuned to coral species. Loss of preferred coral species could have profound effects on reef fish biodiversity, potentially more so than would be predicted on the basis of declining coral cover alone. [ABSTRACT FROM AUTHOR]

Increased habitat diversity is often predicted to promote the diversity of animal communities because a greater variety of habitats increases the opportunities for species to specialize on different resources and coexist. Although positive correlations between the diversities of habitat and associated animals are often observed, the underlying mechanisms are only now starting to emerge, and none have been tested specifically in the marine environment. Scieractinian corals constitute the primary habitat-forming organisms on coral reefs and, as such, play an important role in structuring associated reef fish communities. Using the same field experimental design in two geographic localities differing in regional fish species composition, we tested the effects of coral species richness and composition on the diversity, abundance, and structure of the local fish community. Richness of coral species overall had a positive effect on fish species richness but had no effect on total fish abundance or evenness. At both localities, certain individual coral species supported similar levels of fish diversity and abundance as the high coral richness treatments, suggesting that particular coral species are disproportionately important in promoting high local fish diversity. Furthermore, in both localities, different microhabitats (coral species) supported very different fish communities, indicating that most reef fish species distinguish habitat at the level of coral species. Fish communities colonizing treatments of higher coral species richness represented a combination of those inhabiting the constituent coral species. These findings suggest that mechanisms underlying habitat-animal interaction in the terrestrial environment also apply to marine systems and highlight the importance of coral diversity to local fish diversity. The loss of particular key cOral species is likely to have a disproportionate impact on the biodiversity of associated fish communities. [ABSTRACT FROM AUTHOR]

Transgenerational isotope labelling (TRAIL) using enriched stable isotopes provides a novel means of mass-marking marine fish larvae and estimating larval dispersal. The technique, therefore, provides a new way of addressing questions about demographic population connectivity and larval export from no-take marine protected areas. However, successful field applications must be preceded by larval rearing studies that validate the geochemical marking technique, determine appropriate concentrations and demonstrate that larvae are not adversely affected. Here, we test whether injection of enriched stable barium isotopes (135Ba and 137Ba) at two dose rates produces unequivocal marks on the otoliths of the coral reef grouper Epinephelus fuscoguttatus. We also assess potential negative effects on reproductive performance, egg size, condition and larval growth due to injection of adult female fish. The injection of barium isotopes at both 0.5 and 2.0 mg Ba/kg body weight into the body cavities of gravid female fish was 100% successful in the geochemical tagging of the otoliths of larvae from the first spawning after injection. The low-dose rate produced no negative effects on eggs or larvae. However, the higher dose rate of 2 mg Ba/kg produced small reductions in yolk sac area, oil globule area, standard length and head depth of pre-feeding larvae. Given the success of the 0.5 mg Ba/kg dose rate, it is clearly possible to produce a reliable mark and keep the concentration below any level that could affect larval growth or survival. Hence, enriched Ba isotope injections will provide an effective means of mass-marking grouper larvae. [ABSTRACT FROM AUTHOR]

The persistence of most coastal marine species depends on larvae finding suitable adult habitat at the end of an offshore dispersive stage that can last weeks or months. We tested the effects that ocean acidification from elevated levels of atmospheric carbon dioxide (CO2) could have on the ability of larvae to detect olfactory cues from adult habitats. Larval clownfish reared in control seawater (pH 8.15) discriminated between a range of cues that could help them locate reef habitat and suitable settlement sites. This discriminatory ability was disrupted when larvae were reared in conditions simulating CO2-induced ocean acidification. Larvae became strongly attracted to olfactory stimuli they normally avoided when reared at levels of ocean pH that could occur Ca. 2100 (pH 7.8) and they no longer responded to any olfactory cues when reared at pH levels (pH 7.6) that might be attained later next century on a business-as-usual carbon-dioxide emissions trajectory. If acidification continues unabated, the impairment of sensory ability will reduce population sustainability of many marine species, with potentially profound consequences for marine diversity. [ABSTRACT FROM AUTHOR]

Climate change will impact coral-reef fishes through effects on individual performance, trophic linkages, recruitment dynamics, population connectivity and other ecosystem processes. The most immediate impacts will be a loss of diversity and changes to fish community composition as a result of coral bleaching. Coral-dependent fishes suffer the most rapid population declines as coral is lost; however, many other species will exhibit long-term declines due to loss of settlement habitat and erosion of habitat structural complexity. Increased ocean temperature will affect the physiological performance and behaviour of coral reef fishes, especially during their early life history. Small temperature increases might favour larval development, but this could be counteracted by negative effects on adult reproduction. Already variable recruitment will become even more unpredictable. This will make optimal harvest strategies for coral reef fisheries more difficult to determine and populations more susceptible to overfishing. A substantial number of species could exhibit range shifts, with implications for extinction risk of small-range species near the margins of reef development. There are critical gaps in our knowledge of how climate change will affect tropical marine fishes. Predictions are often based on temperate examples, which may be inappropriate for tropical species. Improved projections of how ocean currents and primary productivity will change are needed to better predict how reef fish population dynamics and connectivity patterns will change. Finally, the potential for adaptation to climate change needs more attention. Many coral reef fishes have geographical ranges spanning a wide temperature gradient and some have short generation times. These characteristics are conducive to acclimation or local adaptation to climate change and provide hope that the more resilient species will persist if immediate action is taken to stabilize Earth’s climate. [ABSTRACT FROM AUTHOR]

Fishes that feed from live corals (corallivores) are a conspicuous component of healthy coral reef environments. However, knowledge of the occurrence and ecological significance of this feeding mode is fragmentary. Historically, very few fish were considered capable of feeding from live coral, and those few that did were considered ecologically insignificant. More recently, the role of corallivores has been re-evaluated; published records document 128 corallivorous fish species from 11 different families, with 69 of these belonging to the family Chaetodontidae. Other families, including the Labridae, Tetraodontidae, Balistidae, Monacanthidae, Pomacentridae and Scaridae, all have between seven and ten coral-feeding species. One-third of coral-feeding fishes feed almost exclusively on corals, with more than 80% of their diet based on coral. Corallivorous fish show distinct prey preferences and consume only a small subset of available corals, usually the genera Acropora, Pocillopora and Porites. This selective predation by corallivores can limit abundance and distribution of preferred corals. Chronic predation by corallivores may also exacerbate effects of coral disturbance (e.g. climate-induced coral bleaching), impeding reef recovery and causing further coral loss. Conversely, the cover of preferred corals can be a primary determinant of corallivore abundance and physiological condition. Owing to this close association, obligate corallivores invariably decline in response to loss of coral cover. Increased knowledge of the number of corallivores and their diets suggest that this feeding mode is more important to coral reef food webs than traditionally thought. [ABSTRACT FROM AUTHOR]

The global degradation of coral reefs is having profound effects on the structure and species richness of associated reef fish assemblages. Historically, variation in the composition of fish communities has largely been attributed to factors affecting settlement of reef fish larvae. However, the mechanisms that determine how fish settlers respond to different stages of coral stress and the extent of coral loss on fish settlement are poorly understood. Here, we examined the effects of habitat degradation on fish settlement using a two-stage experimental approach. First, we employed laboratory choice experiments to test how settlers responded to early and terminal stages of coral degradation. We then quantified the settlement response of the whole reef fish assemblage in a field perturbation experiment. The laboratory choice experiments tested how juveniles from nine common Indo-Pacific fishes chose among live colonies, partially degraded colonies, and dead colonies with recent algal growth. Many species did not distinguish between live and partially degraded colonies, suggesting settlement patterns are resilient to the early stages of declining coral health. Several species preferred live or degraded corals, and none preferred to associate with dead, algal-covered colonies. In the field experiment, fish recruitment to coral colonies was monitored before and after the introduction of a coral predator (the crown-of-thorns starfish) and compared with undisturbed control colonies. Starfish reduced live coral cover by 95–100%, causing persistent negative effects on the recruitment of coral-associated fishes. Rapid reductions in new recruit abundance, greater numbers of unoccupied colonies and a shift in the recruit community structure from one dominated by coral-associated fishes before degradation to one predominantly composed of algal-associated fish species were observed. Our results suggest that while resistant to coral stress, coral death alters the process of replenishment of coral reef fish communities. [ABSTRACT FROM AUTHOR]

Herbivorous fishes have been attributed a central role in structuring benthic communities on coral reefs. However, the relative importance of different behavioural groups of herbivores may differ and their interactions may be complex. This study focuses on an experiment that discriminates between two groups of herbivorous fish: (1) “Foragers” (relatively mobile, schooling grazers, including parrotfishes and surgeonfishes) and (2) “Farmers” (highly site-attached, territorial species, primarily damselfishes). Preliminary observations at Kimbe Bay (Papua New Guinea) showed that both groups were common, and that farmers defended areas from foragers and maintained algal communities that were distinct from the surrounding undefended substratum. An orthogonal combination of a farmer removal treatment and a forager exclusion treatment was applied to isolate their separate effects on algae and corals, and to determine whether farmer territory composition results from forager exclusion or algal cultivation. The experiment showed that foragers had quantitatively greater and qualitatively different effects on sessile benthic community structure than farmers. Where foragers were excluded, there were substantial increases in the cover and biomass of macro-algae and a decline in some corals, regardless of the presence of farmers. Where farmers were removed there was a moderate decline in the cover of some food algal species, regardless of whether foragers had access. No effect of the exclusion of foragers by farmers could be detected. Our results support prevailing views that foragers have a major impact on coral reefs and farmers cultivate selected algae, but challenge the hypothesis that damselfish influence habitat structure by moderating forager disturbance. [ABSTRACT FROM AUTHOR]

Investigates the effects of interspecific competition for coral habitats on the abundance and coexistence of six gobies (Gobiodon) species at Lizard Island in the Great Barrier Reef, Queensland. Habitat use; Competitive ability; Competitor reduction; Habitat overlap; Recolonization.

The biological significance of embryo mortality in demersally spawning coral reef fishes is poorly understood. Here we describe patterns of variation in embryo mortality in Pomacentrus amboinensis (Pomacentridae) at Lizard Island (Great Barrier Reef). The aim was to determine whether numbers of embryos hatched substantially differed from egg production, and if so, identify whether predatory fishes were a source of embryo mortality. Spawning success (number of eggs laid), embryo mortality (proportion of embryos that died prior to hatching) and number of embryos hatching were estimated from daily maps of clutches laid on artificial surfaces (PVC tiles) defended by nesting males. Patterns of variation in eggs laid, embryo mortality and numbers of embryos hatched were examined at three spatial scales: (1) among widely-spaced locations around the island; (2) between adjacent reef slope and patch reef habitats occupied by P. amboinensis at a single location; and (3) among different males within these two habitats. The embryo mortality was extremely high, with a mean of 25.9pm ± 6.2% (S.E.) for 4 locations examined in 1994 and a mean of 69.2pm ± 2.9% for two habitats surveyed in 1995. There were no significant differences in embryo mortality among locations or habitats in either year. This meant that spatial patterns in the number of embryos hatching reflected differences in the number of eggs laid on tiles. Embryo mortality was extremely variable on the scale of individual territories, with embryo mortality commonly ranging from 0% to 100%. Much of the mortality could be attributed to diurnal predatory fishes, especially the wrasse Thalassoma lunare. However, variation in predator densities did not explain spatial patterns in embryo mortality rates. Both solitary and group predatory behaviour was observed, with groups often causing 100% embryo mortality. The level of embryo mortality observed suggests that predation prior to hatching may have a substantial effect on the reproductive output of populations of this demersal-nesting fish. [ABSTRACT FROM AUTHOR]

Marine reserve networks are increasingly implemented to conserve biodiversity and enhance the persistence and resilience of exploited species and ecosystems. However, the efficacy of marine reserve networks in frequently disturbed systems, such as coral reefs, has rarely been evaluated. Here we analyze a well‐mixed larval pool model and a spatially explicit model based on a well‐documented coral trout (Plectropomus spp.) metapopulation in the Great Barrier Reef Marine Park, Australia, to determine the effects of marine reserve coverage and placement (in relation to larval connectivity and disturbance heterogeneity) on the temporal stability of fisheries yields and population biomass in environmentally disturbed systems. We show that marine reserves can contribute to stabilizing fishery yield while increasing metapopulation persistence, irrespective of whether reserves enhance or diminish average fishery yields. However, reserve placement and the level of larval connectivity among subpopulations were important factors affecting the stability and sustainability of fisheries and fish metapopulations. Protecting a mix of disturbed and non‐disturbed reefs, rather than focusing on the least‐disturbed habitats, was the most consistently beneficial approach across a range of dispersal and reserve coverage scenarios. Placing reserves only in non‐disturbed areas was the most beneficial for biomass enhancement, but had variable results for fisheries and could potentially destabilize yields in systems with well‐mixed larval or those that are moderately fished. We also found that focusing protection on highly disturbed areas could actually increase variability in yields and biomass, especially when degraded reef reserves were distant and poorly connected to the meta‐population. Our findings have implications for the design and implementation of reserve networks in the presence of stochastic, patchy environmental disturbances. [ABSTRACT FROM AUTHOR]

Increasing disturbances on coral reefs threaten fish species with close microhabitat associations in shallow waters, but deep reefs may provide refuge habitats. Assessing this potential requires a comprehensive understanding of how versatility in microhabitat use, preference, and selectivity interact with changes in habitat composition along depth gradients. We examined six damselfish species categorized by versatility of shallow-water microhabitat association (‘complex-coral-specialists’, ‘coral-associates’, and ‘generalists’), along a depth gradient from 10 to 30 m in Kimbe Bay, Papua New Guinea, and tested four important hypotheses. (1) We examined associations with hard-coral and complex-coral microhabitats. Hard-coral association declined with depth more among generalists than coral-associates but complex-coral microhabitat association declined for all species except one complex-coral-specialist. (2) We studied whether microhabitat selectivity declines with depth. Unexpectedly, selectivity increased with depth among both generalist and specialist species. (3) Within species, we tested for positive relationships between fish abundance and preferred microhabitat availability at each depth. However, relationships were stochastic across depths for all but one complex-coral-specialist. (4) Finally, we tested for positive relationships between the number of microhabitats selected by a species and the species’ abundance at each depth, finding that species’ abundances were not consistently related to microhabitat versatility. Our results suggest that several species currently utilize deep coral microhabitats (≤ 30 m), including specialists that strongly associate with vulnerable coral habitats in shallow water. Considerable microhabitat plasticity occurred along the gradient, even amidst stable preferences, and versatile species were not habitat limited, though restricted versatility may limit refuge potential for some species. [ABSTRACT FROM AUTHOR]

The world's coral reefs are rapidly transforming, with decreasing coral cover and new species configurations. These new Anthropocene reefs pose a challenge for conservation; we can no longer rely on established management plans and actions designed to maintain the status quo when coral reef habitats, and the challenges they faced, were very different. The key questions now are: what do we want to conserve on Anthropocene reefs, why, and how? Trends in reef management over recent decades reveal rapid shifts in perceived threats, goals and solutions. Future reefs will be unlike anything previously seen by humans, and while their ability to support tourism or fisheries may be relatively resilient, our capacity to manage them may be constrained by their new species configurations. Furthermore, there is a growing spatial mismatch between the escalating scale of threats and current or planned responses. We present a blueprint for future reef conservation that recognizes the need to better understand the processes that maintain Anthropocene reefs, and the growing imperative to reform conservation efforts to address both specific local issues and larger-scale threats. The future of coral reef conservation is no longer one solely of localized action and stewardship; it requires practices and institutions operating at far larger scales than today. • The key questions are: what do we want to conserve on coral reefs, why and how? • We identify scale mismatches between reef stressors and proposed interventions. • Anthropocene reefs require a re-prioritization of critical functions. • The scale of institutions and governance needs to match the scale of stressors. • Cosmetic conservation will not combat the coral reef crisis. [ABSTRACT FROM AUTHOR]

Roving herbivorous fishes play an important role in coral reef communities by removing turf-algae, which can facilitate the settlement of coral larvae. Territorial damselfishes can influence the foraging patterns of roving herbivores by excluding them from their territories, altering the benthic assemblage. However, the impacts depend on the intensity of aggression and which taxonomic groups of roving herbivores are being excluded. Here we document the foraging activity of roving herbivores (Acanthuridae, Scaridae, Siganidae) and the extent to which they are subject to aggression by Pomacentrus adelus , the most abundant territorial damselfish in Kimbe Bay, Papua New Guinea. We then conducted experimental removals (220 m 2 plots on the reef flat) of P. adelus to examine its impact on roving herbivores and the benthic community structure. We hypothesized that the removal of P. adelus would lead to an increase in roving herbivore abundance and foraging activity and a decline in algal cover. The relative abundance (MaxN) and foraging activity (bite rate) of each taxa were examined pre and post-removal using video quadrats. The overall relative abundance of roving herbivores was not influenced by the removal of P. adelus . No changes in foraging patterns were observed for parrotfish, the family that received the highest rate of agonistic interactions, and rabbitfish. The removal of P. adelus resulted in a significant decrease in surgeonfish feeding, suggesting P. adelus alters foraging patterns indirectly through territorial maintenance and not aggression. The only measurable benthic impact of the P. adelus removal was an increase in sediment, while all other substratum types remained constant. These results indicate that P. adelus does not have a negative impact on all roving herbivores and instead may contribute to surgeonfish foraging indirectly through the removal of sediment. The generalisation that territorial damselfish reduce foraging rates of roving herbivores may not be applicable in all systems or for all species. [ABSTRACT FROM AUTHOR]

The scale of larval dispersal of marine organisms is important for the design of networks of marine protected areas. We examined the fate of coral reef fish larvae produced at a small island reserve, using a mass-marking method based on maternal transmission of stable isotopes to offspring. Approximately 60% of settled juveniles were spawned at the island, for species with both short (<2 weeks) and long (>1 month) pelagic larval durations. If natal homing of larvae is a common life-history strategy, the appropriate spatial scales for the management and conservation of coral reefs are likely to be much smaller than previously assumed. [ABSTRACT FROM AUTHOR]