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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]

Dispersal, the movement of individuals away from their natal location to another location, is a basic driver of ecological and evolutionary processes. Direct measures of marine fish larval dispersal have shown that individual dispersal distances vary over several orders of magnitude within a species. We currently do not know the causes of this intraspecific variation. One plausible explanation is dispersal plasticity. Dispersal plasticity, especially as an adaptive parental effect where parents alter the dispersal phenotype of their offspring, is widespread in terrestrial systems, but has yet to be described in marine fishes. In this study, we address a key, although often untested, condition for the evolution of dispersal plasticity as an adaptive parental effect: whether parents can reliably predict the environmental conditions that their offspring will encounter. Using a wild population of orange anemonefish, Amphiprion percula, we investigate habitat quality predictability by testing for spatial autocorrelation in three habitat quality indicators: anemone size, female size, and egg clutch size. We found strong, positive spatial autocorrelation for all three habitat quality indicators to about 500 m. This suggests selection might favor parents that increase allocation to offspring that stay within 500 m if they are in good habitat and increase allocation to offspring that travel farther if they are in poor habitat. Results from this study lay solid foundations for further investigation of dispersal plasticity in A. percula and other marine fishes. Incorporating dispersal plasticity in our investigations of marine fish larval dispersal could contribute to a greater understanding of marine fish metapopulation dynamics, and therefore fisheries recovery and reserve management. [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]

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]

Combining no‐take marine reserves with exclusive access by communities to unreserved waters could provide the required incentives for community management to achieve positive impacts. However, few protected areas have been critically evaluated for their impact, which involves applying counterfactual thinking to predict conditions within protected areas if management had never occurred. Here, we use statistical matching to conduct a rigorous impact evaluation of dual management systems on coral reef fishes in Tonga, with communities having both full no‐take areas and areas of exclusive fishing rights. No‐take areas generally had positive impacts on the species richness, biomass, density, and size of target reef fish, while exclusive access areas were similar to predicted counterfactual conditions. The latter is likely because overall fishing pressure in exclusive access areas might not actually change, although more fish could be exploited by communities with access rights. Our findings suggest that dual management is effective at incentivizing effective community‐based no‐take areas for biodiversity conservation and resource management. [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]

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]

Spatial refuges in peripheral habitats will become increasingly important for species persistence as climate change and other disturbances progressively impact habitat quality and assemblage compositions. However, the capacity for persistence will be determined in part by species‐specific abilities to absorb costs related to altered or decreased quantities and quality of resources at range peripheries.We compared variations in dietary strategies and energy acquisition trade‐offs along depth gradients in two obligate corallivores that differ in level of diet specialization. We also assessed depth‐related changes in energy pathways and energy content of their mixotrophic prey. We found no changes in feeding effort or total resource availability (total coral cover) towards deep range margins, but availability of the preferred resource (Acropora coral) decreased. While both species selectively targeted Acropora, the more specialized species (Chaetodon baronessa) exhibited limited feeding plasticity along the depth gradient. The degree of selectivity towards the preferred coral increased rather than decreased with depth, being 40 times greater than expected, given availability, at their range periphery. In contrast, the generalist's diet (Chaetodon octofasciatus) varied greatly in response to changes in resource availability with depth.Unexpectedly, the energy content of Acropora did not decline with depth, likely due to increased coral heterotrophy in deeper water, indicated by shifts in their molecular isotope geochemistry. This shift was accompanied by a 20% increase in plankton‐sourced carbon in the muscle tissue of deep‐resident fish, despite no observations of direct feeding on plankton food sources.Our results indicate that deep ranges in coral‐obligate reef fishes are supported by multiple mechanisms of trophic versatility in both the fish and corals. This nutritional plasticity likely serves a compensatory role in the resilience and eventual adaptation of organisms at their range peripheries.For species vulnerable to increasing anthropogenic impacts at range cores, variable and multi‐trophic functional responses can act to buffer against costs and increase the refuge potential of range peripheries. Specialist consumers may also be supported indirectly at range margins via trophic plasticity within their preferred prey. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "Coral reef fish smell leaves to find island homes " which appeared in the 26 August 2008 issue.

Many vertebrates form monogamous pairs to mate and care for their offspring. However, genetic tools have increasingly shown that offspring often arise from matings outside of the monogamous pair bond. Social monogamy is relatively common in coral reef fishes, but there have been few studies that have confirmed monogamy or extra‐pair reproduction, either for males or for females. Here, long‐term observations and genetic tools were applied to examine the parentage of embryos in a paternally mouth‐brooding cardinalfish, Sphaeramia nematoptera. Paternal care in fishes, such as mouth‐brooding, is thought to be associated with a high degree of confidence in paternity. Two years of observations confirmed that S. nematoptera form long‐term pair bonds within larger groups. However, genetic parentage revealed extra‐pair mating by both sexes. Of 105 broods analysed from 64 males, 30.1% were mothered by a female that was not the partner and 11.5% of broods included eggs from two females. Despite the high paternal investment associated with mouth‐brooding, 7.6% of broods were fertilized by two males. Extra‐pair matings appeared to be opportunistic encounters with individuals from outside the immediate group. We argue that while pair formation contributes to group cohesion, both males and females can maximize lifetime reproductive success by taking advantage of extra‐pair mating opportunities. [ABSTRACT FROM AUTHOR]

Escalating climate-related disturbances and asymmetric habitat losses will increasingly result in species living in more marginal habitats. Marginal habitats may represent important refuges if individuals can acquire adequate resources to survive and reproduce. However, resources at range margins are often distributed more sparsely; therefore, increased effort to acquire resources can result in suboptimal performance and lead to marginal populations becoming non-self-sustaining sink-populations. Shifting resource availability is likely to be particularly problematic for dietary specialists. Here, we use extensive in situ behavioural observations and physiological condition measurements to examine the costs and benefits of resourceacquisition along a depth gradient in two obligate corallivore reef fishes with contrasting levels of dietary specialization. As expected, the space used to secure coral resources increased towards the lower depth margin. However, increased territory sizes resulted in equal or greater availability of resources within deeper territories. In addition, we observed decreased competition and no differences in foraging distance, pairing behaviour, body condition or fecundity at greater depths. Contrary to expectation, our results demonstrate that coral-obligate fishes can select high-quality coral patches on the deeper-reef to access equal or greater resources than their shallow-water counterparts, with no extra costs. This suggests depth offers a viable potential refuge for some at-risk coral-specialist fishes. [ABSTRACT FROM AUTHOR]

The size and structure of social groups of animals can be governed by a range of ecological factors and behavioral interactions. In small, highly site-attached coral reef fishes, group size is often constrained by the size of the habitat patch they are restricted to. However, group size may also be influenced by changes in abundance along important environmental gradients, such as depth or distance offshore. In addition, the body size and sex structure within social groups can be determined by the size of the habitat patch and the dominance relationships among group members. Here we examined the roles of ecological factors and behavioral interactions in governing group size and structure in the orange clownfish, Amphiprion percula, on inshore reefs in Kimbe Bay, Papua New Guinea. We quantified relationships between ecological variables (anemone size, depth, and distance from shore) and social group variables (group size, and total body length of the three largest individuals (ranks 1, 2, and 3)). Anemone size explained the greatest amount of variation in group variables, with strong, positive relationships between anemone surface area and group size, and total length of individuals ranked 1, 2, and 3. Group structure was also weakly correlated with increasing depth and distance from shore, most likely through the indirect effects of these environmental gradients on anemone size. Variation in group size and the lengths of ranks 2 and 3 were all closely related to the length of rank 1. Path analysis indicated that anemone size has a strong direct effect on the length of rank 1. In turn, the length of rank 1 directly affects the size of the subordinate individuals and indirectly affects the group size through its influence on subordinates. Hence, anemone size directly and indirectly controls social group size and structure in this space-limited fish species. It is also likely that anemonefish have feedback effects on anemone size, although this could not be differentiated in the path analysis. [ABSTRACT FROM AUTHOR]

Abstract: Marine reserves are a commonly applied conservation tool, but their size is often chosen based on considerations of socioeconomic rather than ecological impact. Here, we use a simple individual‐based model together with the latest empirical information on home ranges, densities and schooling behaviour in 66 coral reef fishes to quantify the conservation effectiveness of various reserve sizes. We find that standard reserves with a diameter of 1–2 km can achieve partial protection (≥50% of the maximum number of individuals) of 56% of all simulated species. Partial protection of the most important fishery species, and of species with diverse functional roles, required 2–10 km wide reserves. Full protection of nearly all simulated species required 100 km wide reserves. Linear regressions based on the mean home range and density, and even just the maximum length, of fish species approximated these results reliably, and can therefore be used to support locally effective decision making. [ABSTRACT FROM AUTHOR]

Colonial animals often form stable pair bonds, returning to the same site to breed with the same partner every year. Familiarity with both partner and breeding site has the potential to enhance an individual’s reproductive success. However, it is often unknown whether the mating system arises because of site fidelity, mate fidelity or both. Here, observational and experimental studies are used to identify causal links between site fidelity and pair formation in a group-living coral reef cardinalfish, Sphaeramia nematoptera. A long-term field tagging study was undertaken to quantify site and mate attachment. This was followed by both mate removal and mate transplant experiments to test whether the prolonged association with home sites was primarily because of mate or site fidelity. Adult S. nematoptera exhibited a prolonged association with home sites and partners, with some pairs lasting more than 4 months at the same site. A Bayesian mixed effect model showed that individuals in pairs were more likely to remain site attached, regardless of sex and maturity. Following mate removal, 78% of S. nematoptera found a new partner within 2 weeks on the same site, supporting the hypothesis that individuals primarily exhibit site fidelity. This was confirmed by the partner translocation experiment, with only 1 of 24 fish following their translocated partner to a new site. In these cardinalfish, strong site attachment facilitates long-lasting pair bonds, as well as new pair formation when necessary, suggesting that site rather than mate fidelity is the major driver of the reproductive system. [ABSTRACT FROM AUTHOR]

Coral reefs are highly diverse ecosystems, where numerous closely related species often coexist. How new species arise and are maintained in these high geneflow environments have been long-standing conundrums. Hybridization and patterns of introgression between sympatric species provide a unique insight into the mechanisms of speciation and the maintenance of species boundaries. In this study, we investigate the extent of hybridization between two closely related species of coral reef fish: the common coral trout ( Plectropomus leopardus) and the bar-cheek coral trout ( Plectropomus maculatus). Using a complementary set of 25 microsatellite loci, we distinguish pure genotype classes from first- and later-generation hybrids, identifying 124 interspecific hybrids from a collection of 2,991 coral trout sampled in inshore and mid-shelf reefs of the southern Great Barrier Reef. Hybrids were ubiquitous among reefs, fertile and spanned multiple generations suggesting both ecological and evolutionary processes are acting to maintain species barriers. We elaborate on these finding to investigate the extent of genomic introgression and admixture from 2,271 SNP loci recovered from a dd RAD library of pure and hybrid individuals. An analysis of genomic clines on recovered loci indicates that 261 SNP loci deviate from a model of neutral introgression, of which 132 indicate a pattern of introgression consistent with selection favouring both hybrid and parental genotypes. Our findings indicate genome-wide, bidirectional introgression between two sympatric species of coral reef fishes and provide further support to a growing body of evidence for the role of hybridization in the evolution of coral reef fishes. [ABSTRACT FROM AUTHOR]

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no-take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40 km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers ( Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60-220 km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P. maculatus and 17 juvenile P. leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short-distance larval dispersal within regions (200 m to 50 km) and long-distance, multidirectional dispersal of up to ~250 km among regions. Dispersal strength declined significantly with distance, with best-fit dispersal kernels estimating median dispersal distances of ~110 km for P. maculatus and ~190 km for P. leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long-distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations. [ABSTRACT FROM AUTHOR]

Natal philopatry, the return of individuals to their natal area for reproduction, has advantages and disadvantages for animal populations. Natal philopatry may generate local genetic adaptation, but it may also increase the probability of inbreeding that can compromise persistence. Although natal philopatry is well documented in anadromous fishes, marine fish may also return to their birth site to spawn. How philopatry shapes wild fish populations is, however, unclear because it requires constructing multigenerational pedigrees that are currently lacking for marine fishes. Here we present the first multigenerational pedigree for a marine fish population by repeatedly genotyping all individuals in a population of the orange clownfish (Amphiprion percula) at Kimbe Island (Papua New Guinea) during a 10-y period. Based on 2927 individuals, our pedigree analysis revealed that longitudinal philopatry was recurrent over five generations. Progeny tended to settle close to their parents, with related individuals often sharing the same colony. However, successful inbreeding was rare, and genetic diversity remained high, suggesting occasional inbreeding does not impair local population persistence. Local reproductive success was dependent on the habitat larvae settled into, rather than the habitat they came from. Our study suggests that longitudinal philopatry can influence both population replenishment and local adaptation of marine fishes. Resolving multigenerational pedigrees during a relatively short period, as we present here, provides a framework for assessing the ability of marine populations to persist and adapt to accelerating climate change. [ABSTRACT FROM AUTHOR]

Coral reef communities between 26.8°N and 18.6°N latitude in the Saudi Arabian Red Sea were surveyed to provide baseline data and an assessment of fine-scale biogeography of communities in this region. Forty reefs along 1100 km of coastline were surveyed using depth-stratified visual transects of fish and benthic communities. Fish abundance and benthic cover data were analyzed using multivariate approaches to investigate whether coral reef communities differed with latitude. A total of 215 fish species and 90 benthic categories were recorded on the surveys. There were no significant differences among locations in fish abundance, species richness, or among several diversity indices. Despite known environmental gradients within the Red Sea, the communities remained surprisingly similar. The communities do, however, exhibit subtle changes across this span of reefs that likely reflect the constrained distributions of several species of reef fish and benthic fauna. [ABSTRACT FROM AUTHOR]

Although competition is recognized as a core ecological process, its prevalence and importance in coral reef fish communities have been debated. Here we compile and synthesize the results of 173 experimental tests of competition from 72 publications. We show that evidence for competition is pervasive both within and between species, with 72% of intraspecific tests and 56% of interspecific tests demonstrating a demographically significant consequence of competition (e.g., a decrease in recruitment, survival, growth, or fecundity). We highlight several factors that can interact with the effects of competition and make it more difficult to detect in field experiments. In light of this evidence, we discuss the role of competition in shaping coral reef fish communities and competition's status as one of several processes that contribute to species coexistence. Finally, we consider some of the complex ways that climate change may influence competition, and we provide suggestions for future research. [ABSTRACT FROM AUTHOR]

Habitat degradation is predicted to exacerbate competition for critical resources; however, the relationship between habitat quality and competition is poorly understood. In this study, we used a manipulative experiment to test the effects of habitat degradation on competition between two planktivorous, coral-dwelling damselfishes, Chrysiptera parasema and Dascyllus melanurus. Experimental reefs were constructed with either healthy (100% live) or degraded (10% live) Acropora longicyathus coral, stocked with varying densities of these two fish species, and monitored for two months. On healthy habitat, the mortality of C. parasema was density dependent, and increased substantially in the presence of the dominant interspecific competitor D. melanurus. In contrast, on reefs where habitat was degraded, C. parasema mortality was highly variable, density independent, and was no longer influenced by the presence of dominant competitor D. melanurus. Behavioral observations revealed that agonistic interactions for both species increased with density on degraded habitat, but not on healthy habitat. In addition, on degraded reefs, both species displayed a reduced association with reef habitat and ventured further away from shelter with increasing densities of the dominant competitor D. melanurus. These results suggest that reduced habitat quality can have such a profound effect on reef fishes, that it eliminates density-dependent mortality and competitive dominance hierarchies, thereby substantially altering the mechanisms that structure reef fish communities. [ABSTRACT FROM AUTHOR]

Microsatellites are often considered ideal markers to investigate ecological processes in animal populations. They are regularly used as genetic barcodes to identify species, individuals, and infer familial relationships. However, such applications are highly sensitive the number and diversity of microsatellite markers, which are also prone to error. Here, we propose a novel framework to assess the suitability of microsatellite datasets for parentage analysis and species discrimination in two closely related species of coral reef fish, Plectropomus leopardus and P. maculatus ( Serranidae). Coral trout are important fisheries species throughout the Indo-Pacific region and have been shown to hybridize in parts of the Great Barrier Reef, Australia. We first describe the development of 25 microsatellite loci and their integration to three multiplex PCRs that co-amplify in both species. Using simulations, we demonstrate that the complete suite of markers provides appropriate power to discriminate between species, detect hybrid individuals, and resolve parent-offspring relationships in natural populations, with over 99.6% accuracy in parent-offspring assignments. The markers were also tested on seven additional species within the Plectropomus genus with polymorphism in 28-96% of loci. The multiplex PCRs developed here provide a reliable and cost-effective strategy to investigate evolutionary and ecological dynamics and will be broadly applicable in studies of wild populations and aquaculture brood stocks for these closely related fish species. [ABSTRACT FROM AUTHOR]

Increasing sediment input into coastal environments is having a profound influence on shallow marine habitats and associated species. Coral reef ecosystems appear to be particularly sensitive, with increased sediment deposition and re-suspension being associated with declines in the abundance and diversity of coral reef fishes. While recent research has demonstrated that suspended sediment can have negative impacts on post-settlement coral reef fishes, its effect on larval development has not been investigated. In this study, we tested the effects of different levels of suspended sediment on larval growth and development time in Amphiprion percula, a coral reef damselfish. Larvae were subjected to four experimental concentrations of suspended sediment spanning the range found around coastal coral reefs (0-45 mg l-1). Larval duration was significantly longer in all sediment treatments (12 days) compared with the average larval duration in the control treatment (11 days). Approximately 75% of the fish in the control had settled by day 11, compared with only 40-46% among the sediment treatments. In the highest sediment treatment, some individuals had a larval duration twice that of the median duration in the control treatment. Unexpectedly, in the low sediment treatment, fish at settlement were significantly longer and heavier compared with fish in the other treatments, suggesting delayed development was independent of individual condition. A sediment-induced extension of the pelagic larval stage could significantly reduce numbers of larvae competent to settle and, in turn, have major effects on adult population dynamics. [ABSTRACT FROM AUTHOR]

In the terrestrial environment, endemic species and isolated populations of widespread species have the highest rates of extinction partly due to their low genetic diversity. To determine if this pattern holds in the marine environment, we examined genetic diversity in endemic coral reef angelfishes and isolated populations of widespread species. Specifically, this study tested the prediction that angelfish (genus: Centropyge) populations at Christmas and Cocos Islands have low genetic diversity. Analyses of a 436 base pair fragment of the mtDNA control region revealed that the endemic C. joculator exhibited high haplotype (h > 0.98 at both locations) and nucleotide (Christmas % = 3.63, Cocos % = 9.99) diversity. Similarly, isolated populations of widespread angelfishes (C. bispinosa and C. flavicauda) had high haplotype (h > 0.98) and nucleotide (% = 2.81 and % = 5.78%, respectively) diversity. Therefore, in contrast to terrestrial patterns, endemic and isolated populations of widespread angelfishes do not have low genetic diversity, rather their haplotype and nucleotide diversities were among the highest reported for marine fishes. High genetic diversity should reduce extinction risk in these species as it could provide the evolutionary potential to adapt to the rapidly changing environmental conditions forecast for coral reefs. [ABSTRACT FROM AUTHOR]

The relationship between genetic diversity and species diversity provides insights into biogeography and historic patterns of evolution and is critical for developing contemporary strategies for biodiversity conservation. Although concordant large-scale clines in genetic and species diversity have been described for terrestrial organisms, whether these parameters co-vary in marine species remains largely unknown. We examined patterns of genetic diversity for 11 coral reef fish species sampled at three locations across the Pacific Ocean species diversity gradient (Australia: ∼1600 species; New Caledonia: ∼1400 species; French Polynesia: ∼800 species). Combined genetic diversity for all 11 species paralleled the decline in species diversity from West to East, with French Polynesia exhibiting lowest total haplotype and nucleotide diversities. Haplotype diversity consistently declined toward French Polynesia in all and nucleotide diversity in the majority of species. The French Polynesian population of most species also exhibited significant genetic differentiation from populations in the West Pacific. A number of factors may have contributed to the general positive correlation between genetic and species diversity, including location and time of species origin, vicariance events, reduced gene flow with increasing isolation, and decreasing habitat area from West to East. However, isolation and habitat area, resulting in reduced population size, are likely to be the most influential. [ABSTRACT FROM AUTHOR]

Aim To determine the applicability of biogeographical and ecological theory to marine species at two remote island locations. This study examines how biogeography, isolation and species geographic range size influence patterns of species richness, endemism, species composition and the abundance of coral reef fishes. Location Christmas Island and the Cocos (Keeling) Islands in the tropical eastern Indian Ocean. Methods Published species lists and underwater visual surveys were used to determine species richness, endemism, species composition and abundance of reef fishes at the islands. These data were statistically compared with patterns of species composition and abundance from the neighbouring 'mainland' Indonesian region. Results The two isolated reef fish communities were species-poor and contained a distinct taxonomic composition with an overrepresentation of species with high dispersal potential. Despite low species richness, we found no evidence of density compensation, with population densities on the islands similar to those of species-rich mainland assemblages. The mix of Indian and Pacific Ocean species and the proportional representations of the various regional faunas in the assemblages were not influenced by the relative proximity of the islands to different biogeographical provinces. Moreover, species at the edge of their range did not have a lower abundance than species at the centre of their range, and endemic species had substantially higher abundances than widespread species. At both locations, endemism was low (less than 1.2% of the community); this may be because the locations are not sufficiently isolated or old enough to promote the evolution of endemic species. Main conclusions The patterns observed generally conform to terrestrial biogeographical theory, suggesting that similar processes may be influencing species richness and community composition in reef fish communities at these remote islands. However, species abundances differed from typical terrestrial patterns, and this may be because of the life history of reef fishes and the processes maintaining isolated populations. [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]

Disturbance can result in the fragmentation and/or loss of suitable habitat, both of which can have important consequences for survival, species interactions, and resulting patterns of local diversity. However, effects of habitat loss and fragmentation are typically confounded during disturbance events, and previous attempts to determine their relative significance have proved ineffective. Here we experimentally manipulated live coral habitats to examine the potential independent and interactive effects of habitat loss and fragmentation on survival, abundance, and species richness of recruitment-stage, coral-associated reef fishes. Loss of 75% of live coral from experimental reefs resulted in low survival of a coral-associated damselfish and low abundance and richness of other recruits 16 weeks after habitat manipulations. In contrast, fragmentation had positive effects on damselfish survival and resulted in greater abundance and species richness of other recruits. We hypothesize that spacing of habitat through fragmentation weakens competition within and among species. Comparison of effect sizes over the course of the study period revealed that, in the first six weeks following habitat manipulations, the positive effects of fragmentation were at least four times stronger than the effects of habitat loss. This initial positive effect of fragmentation attenuated considerably after 16 weeks, whereas the negative effects of habitat loss increased in strength over time. There was little indication that the amount of habitat influenced the magnitude of the habitat fragmentation effect. Numerous studies have reported dramatic declines in coral reef fish abundance and diversity in response to disturbances that cause the loss and fragmentation of coral habitats. Our results suggest that these declines occur as a result of habitat loss, not habitat fragmentation. Positive fragmentation effects may actually buffer against the negative effects of habitat loss and contribute to the resistance of reef fish populations to declines in coral cover. [ABSTRACT FROM AUTHOR]

The article presents a study on the recruitment and persistence of coral-dwelling fishes at a natural coral bleaching event in Kimbe Bay, Papua New Guinea. The research involves tagging the healthy, severely bleached, and dying colonies of corymbose Acropora species (spp.), and monitoring its resident fish communities. There was no difference in the mean number of Pomacentrus moluccensis recruits that settled on healthy versus bleached corals, but the number of recruits on dead colonies was lower after 4 weeks and the frequency of recruit selection was lower on dead colonies. Furthermore, the results show that coral-dwelling fishes do not avoid bleached corals at settlement but will quickly disappear if corals die from bleaching.

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]

Many species of coral reef fishes form pairs. While it is assumed that pairs represent the breeding unit of these species, the reproductive status of paired versus solitary individuals, and changes in status associated with pair-formation have seldom been investigated. In order to assess whether pairing is related to reproduction we examined whether the ontogenetic timing of pair formation coincided with the onset of maturation in four species of fishes: Chaetodon lunulatus and Chaetodon melannotus (family Chaetodontidae), and Valenciennea muralis and Valenciennea strigata (family Gobiidae). 65-78% of all fishes occurred in pairs. In C. lunulatus and V. muralis, pair-formation coincided with maturation, suggesting that these species form pairs for breeding. Further, C. lunulatus and V. muralis exhibited significant positive size-assortative pairing, which is often associated with monogamous mating. In contrast, pair formation in C. melannotus and V. strigata did not coincide with maturation. In both these species many solitary individuals were reproductive, and same sex pairs were common. While reproduction may be the basis for pairing in some species, both solitary and paired individuals are capable of breeding in others. We propose that non-reproductive mechanisms, such as predator vigilance, may explain pair-formation in coral reef fishes with non-monogamous breeding systems. [ABSTRACT FROM AUTHOR]

Many recognised species of coral reef fishes exhibit two or more colour variants, but it is unknown whether these represent genetically identical phenotypes, genetic polymorphisms or closely related species. We tested between these alternatives for two colour morphs of the coral reef fish, Pseudochromis fuscus, from Lizard Island (Great Barrier Reef). A molecular analysis using mtDNA did not detect any genetic differentiation between co-occurring ‘yellow’ and ‘brown’ colour morphs. A previous study proposed that these two colour morphs are aggressive mimics of yellow and brown damselfishes. Here, a manipulative field experiment was used to evaluate whether the colour dimorphism in P. fuscus is a phenotypic response to the presence of two different model species. Colonies of either yellow or brown damselfish species were established on different patch reefs, and each of the two different P. fuscus morphs was then placed on the different reefs. Contrary to expectations, all yellow individuals that stayed on the reefs changed to brown, regardless of the model species. No brown individuals changed to the yellow colouration. However, P. fuscus were more likely to emigrate from, or suffer higher mortality on, patch reefs where they were not matched with similarly coloured models. Clearly, yellow and brown P. fuscus are members of a single species with sufficient phenotypic plasticity to switch from yellow to brown colouration. [ABSTRACT FROM AUTHOR]

Summary: Population connectivity through larval dispersal is an essential parameter in models of marine population dynamics [1–3] and the optimal size and spacing of marine reserves [4–6]. However, there are remarkably few direct estimates of larval dispersal for marine organisms, and the actual birth sites of successful recruits have never been located. Here, we solve the mystery of the natal origin of clownfish (Amphiprion polymnus) juveniles by mass-marking via tetracycline immersion all larvae produced in a population. In addition, we established parentage by DNA genotyping all potential adults and all new recruits arriving in the population. Although no individuals settled into the same anemone as their parents, many settled remarkably close to home. Even though this species has a 9–12 day larval duration, one-third of settled juveniles had returned to a 2 hectare natal area, with many settling <100 m from their birth site. This represents the smallest scale of dispersal known for any marine fish species with a pelagic larval phase. The degree of local retention indicates that marine reserves can provide recruitment benefits not only beyond but also within their boundaries. [Copyright &y& Elsevier]

A number of potential mimetic relationships between coral reef fishes have been described, but the underlying mechanisms are poorly understood. Similarities in colour between species have often been attributed to aggressive mimicry (where predators resemble models in order to deceive prey), however this has not been tested. The fang blenny, Plagiotremus rhinorhynchos is a specialized predator that feeds on tissues of other fishes. Some individuals appear to mimic the harmless cleaner wrasse Labroides dimidiatus in order to deceive fish visiting cleaning stations, thereby increasing access to food. In this study, the ecological relationship between the mimic and model was examined at Kimbe Bay (Papua New Guinea) and the hypothesis that colour similarities represent facultative aggressive mimicry was experimentally evaluated. Some juveniles exhibited a striking resemblance to the juvenile colouration of the cleaner wrasse, but only when in close proximity to the wrasse and only when similar in size. As predicted for mimics, P. rhinorhynchos co-occurred with L. dimidiatus, but was rare relative to the model. Among site comparisons showed that the abundance of mimetic type blennies was positively correlated with the abundance of juvenile cleaner wrasses. Approximately 50% of all P. rhinorhynchos were found ≤1 m from the nearest L. dimidiatus, a distance significantly shorter than expected if they were not associated. A cleaner wrasse removal experiment was carried out to test whether the colour displayed by the blenny and its foraging success were contingent upon the presence of a model. In all cases, removal of the model prompted a rapid colour change to a general non-mimetic colouration in P. rhinorhynchos. Removal of L. dimidiatus also resulted in a ~20% reduction in the average foraging success of the blenny compared to controls, supporting the hypothesis that the blenny is a facultative aggressive mimic of the cleaner wrasse. [ABSTRACT FROM AUTHOR]

Correlations between abundance of organisms and their habitat have often been used as a measure of the importance of particular habitat features. However, experimental manipulation of the habitat provides a more unequivocal estimate of its importance. In this study we quantified how fish communities on small patch reefs covaried with changes in benthic cover habitat features. A random sample of small patch reefs was selected and both fish abundance and habitat measures recorded. Naturally occurring patch reefs could be classed into three habitat types based on their benthic cover. Reefs dominated by massive soft corals were the most abundant (50%), followed by those dominated by rock and soft corals in equal proportions (36%), then reefs dominated by branching corals (14%). Fish assemblages differed between the reef types. Communities on soft-coral-dominated and rock/soft-coral-dominated patch reefs formed a continuum of species responses correlated with degree of soft coral cover. In contrast, branching-coral-dominated reefs were occupied by a more discrete set of species. We tested the role of soft corals in contributing to this pattern by experimentally reducing soft coral cover on patch reefs from a baseline level of ~67% to ~33% and ~6%, and monitoring the experiment over 2 years. Contrary to expectations derived from the correlative data, and in contrast with previous manipulations of hard corals, soft-coral disturbance did not generate any corresponding changes in the fish assemblage. This "negative" result indicated that the quality and heterogeneity of habitat generated by soft corals on patch reefs was indistinguishable from equivalent-sized habitat patches formed by bare rock alone. Nevertheless, because soft corals are living organisms they have the potential to generate indirect effects by interacting with other organisms such as hard corals. In the long-term, we hypothesize that biotic interactions between habitat forming organisms might affect composition of fish assemblages on patch reefs. [ABSTRACT FROM AUTHOR]

Examines the effects of fish removal and habitat disturbance on the structure of fish assemblages occupying small coral patch reefs at Lizard Island, Australia. Importance of distrubance in the dynamics of a wide variety of ecological communities; Effect of disturbance-induced heterogeniety into patches; Central role of habitat as a mediator of interactions.

An experiment on a coral reef fish is described that assesses the effects of recruitment success on adult abundance over a 3-yr period. The damselfish Pomacentrus amboinensis was examined on natural patch reefs of °8 m2 in the lagoon of One Tree Reef. Recruitment levels were adjusted to 0, 0.5, 1, and 2 recruits m-2°yr-1 by transplanting juveniles among reefs at the end of four successive recruitment seasons (with four replicates per treatment). Natural recruitment success was monitored on 16 undisturbed reefs, and adult numbers were monitored at irregular intervals on both experimental and undisturbed reefs. The adult population density at the end of the experiment increased significantly with recruitment within the 0-1 recruit/m2 range. However, doubling recruitment from 1 to 2 recruits/m2 did not lead to any further increase in adult density. The recruitment treatments did not affect adult density until a 2-yr period had elapsed (corresponding to average maturation time). At this time, treatments receiving 1 and 2 recruits/m2 showed a dramatic increase in adult numbers, whereas in the low-recruitment treatments, adult densities declined. The experiment indicated that a recruitment success of between 0.5 and 1 recruit/m2 was necessary to maintain adult numbers at pre-experimental levels. Natural recruitment success was highly variable among years, but adult densities remained relatively constant over time at °0.8 adult/m2. Differences in the final adult densities among reefs were correlated with average recruitment levels, but above 0.8-1.0 recruit/m2, adult densities did not increase with increasing recruitment success. The results from experimental and undisturbed reefs suggest that natural variation in recruitment success affects the importance of post-recruitment processes. In good recruitment years, adult densities on a substantial number of reefs may be limited by density-dependent processes, which may affect the majority of individuals in a region. Density-dependent juvenile growth may buffer adult populations on these reefs against the effects of poor recruitment years, since input may come from a number of immature age classes. Where recruitment success is always below a certain level, the dynamics of adult populations will reflect variation in recruitment success. [ABSTRACT FROM AUTHOR]

Aquatic animals commonly rely on chemical cues to provide information regarding their surroundings. They can respond either by being attracted to (potential mates, preferred habitats) or avoiding (predators, competitors) the source of the stimuli. Coral reef fishes use chemical cues to detect habitats, avoid predators and recognise conspecifics. However, the extent to which chemical cues are used to detect and respond to potential competitors, has received little attention. Here we test olfactory preferences for conspecifics and heterospecifics in newly settled juvenile coral reef fishes. Juveniles of 4 common coral-associated damselfish species: Dascyllus melanurus , Dascyllus reticulatus , Chrysiptera arnazae and Pomacentrus moluccensis, were subjected to olfactory choice tests. Three of the 4 species (excluding P. moluccensis ) demonstrated preferences for waterborne conspecifics odours. All species exhibited an avoidance towards heterospecific odours; this aversion was consistently greatest towards P. moluccensis . A neutral response toward heterospecifics was only evident in two instances (1) between the two congeneric Dascyllus species, with D. melanurus toward D. reticulatus, and (2) with C. arnazae toward D. melanurus . While it is already known that the presence of conspecifics plays a vital role in settlement site selection, we show here that the presence of heterospecifics may also be key in determining the spatial distributions of juveniles across areas of coral reef. [ABSTRACT FROM AUTHOR]

Abstract: Coral reef fish use olfaction to respond to a variety of chemical cues that allow them to detect predators, the presence of resident conspecifics and the ‘smell’ of reef water. However, whether olfaction is utilised by juvenile reef fish for discerning among the multiple microhabitat types present on the reef is not known. Additionally the relative importance of chemical cues emitted from habitat types versus those from resident individuals to juveniles has not been assessed. The ability to distinguish and use such cues could be critical in determining spatial distributions of juveniles across coral reef areas. Here we test olfactory preferences for conspecifics, coral health and different branching coral species in newly recruited juveniles of coral reef fishes. Newly settled juveniles of three common coral associated species in Kimbe Bay, Papua New Guinea, Dascyllus melanurus, Chrysiptera parasema and Chaetodon octofasciatus, were subjected to a series of pairwise olfactory choice tests using two-channel choice flume. All three species exhibited a significant preference for the scent of conspecifics (60–70%) and live coral (60–70%) over water with no associated reef cues. All species strongly avoided the odour of degraded coral (≥80%). Only one species, D. melanurus showed olfactory discrimination among branching coral species, favouring Pocillopora damicornis over Acropora spp. Our results indicate that olfactory preferences for both conspecifics and live coral may combine to determine juvenile and recruitment distribution patterns in these species and local population declines in response to coral degradation but do not necessarily contribute to specific coral habitat associations. [Copyright &y& Elsevier]

Abstract: Although the global decline in coral reef health is likely to have profound effects on reef associated fishes, these effects are poorly understood. While declining coral cover can reduce the abundance of reef fishes through direct effects on recruitment and/or mortality, recent evidence suggests that individuals may survive in disturbed habitats, but may experience sublethal reductions in their condition. This study examined the response of 2 coral associated damselfishes (Pomacentridae), Chrysiptera parasema and Dascyllus melanurus, to varying levels of live coral cover. Growth, persistence, and the condition of individuals were quantified on replicate coral colonies in 3 coral treatments: 100% live coral (control), 50% live coral (partial) and 0% live coral (dead). The growth rates of both species were directly related to the percentage live coral cover, with individuals associated with dead corals exhibiting the slowest growth, and highest growth on control corals. Such differences in individual growth between treatments were apparent after 29 d. There was no significant difference in the numbers of fishes persisting or the physiological condition of individuals between different treatments on this time-scale. Slower growth in disturbed habitats will delay the onset of maturity, reduce lifetime fecundity and increase individual''s vulnerability to gape-limited predation. Hence, immediate effects on recruitment and survival may underestimate the longer-term impacts of declining coral on the structure and diversity of coral-associated reef fish communities. [Copyright &y& Elsevier]

Availability of specific microhabitat exerts a strong influence on recruitment and abundance of coral reef fishes, but the ecological basis for microhabitat selection is not always clear. This study used a combination of field-based sampling and aquarium-based experiments to test microhabitat preferences of juvenile coral trout (mostly, Plectropomus maculatus), and assess whether microhabitat selection is related to prey access. In the field, coral trout use live Acropora corals situated over sand 3 times more than any other microhabitat, even through these specific microhabitats accounted for only 12.8% of habitat area. Field-based surveys revealed that live coral habitats support higher densities of potential prey species (71.73individuals per m2 ±8.4SE for fish; 423.36individuals per m2 ±91.8SE for crustacean) compared to dead corals (21.92individuals per m2 ±3.9SE for fish; 146.67individuals per m2 ±38.1SE for crustacean). Furthermore, structural microhabitats on sand have higher densities of prey (57.61individuals per m2 ±9.6SE for fish; 539.04individuals per m2 ±79.0SE for crustacean) compared to comparable microhabitats on consolidated carbonate substrata (36.05individuals per m2 ±6.7SE for fish; 129.36individuals per m2 ±15.9SE for crustacean). In the absence of prey, juvenile coral trout did not distinguish between live versus dead corals (37.18%±8.2SE and 35.48%±6.1SE), but both of these microhabitats were preferred over rubble (16.21%±3.5SE), macroalgae (11.09%±6.1SE) and sand (0%). In tank-based studies of prey use, juvenile coral trout consumed prey fishes that associate with non-coral habitats (e.g., Eviota zebrina; 33.28%±3.4SE) and mid water species (e.g., Aioliops tetrophthalmus; 47.97%±2.8SE), but did not consume those fishes with an obligate association with live corals (4.7%±1.9SE; 6.03%±2.2SE; 7.9%±2.8SE). Our results suggest that studies of microhabitat preferences should consider both the structure and location of specific microhabitats. It is presumed that structural microhabitats are essential for evading predators, while occupation of live corals positioned over sandy substrata maximizes accessibility to a diverse array of potential prey fishes and crustaceans. [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]

Summary: Understanding why and how subordinates of many social animals remain consistently smaller than dominants is important for determining the mechanisms underlying the structure and stability of hierarchical societies. Here we show that competition over food and conflict over social rank are ultimately responsible for the regulation of subordinate growth in the group-living reef fish, Paragobiodon xanthosomus (Gobiidae). Subordinates benefit from reducing their own food intake, and hence growth, when they approach a size where they risk conflict with dominants. Dieting appears to be a behavioural mechanism ensuring that subordinates remain smaller than dominants within the hierarchy. [Copyright &y& Elsevier]