Reef Fish Species Richness Research Articles

Regional-scale disturbances drive long-term decline of inshore coral reef fish assemblages in the Great Barrier Reef Marine Park.

Anthropogenic pressure is increasing the variety and frequency of environmental disturbance events, limiting recovery and leading to long-term declines in wild plant and animal populations. Coral reefs and associated fish assemblages are inherently dynamic due to their susceptibility to a host of disturbances, but regional-scale nuances in the drivers of long-term change frequently remain poorly resolved. Here, we examine the effects of multiple potential drivers of change in coral reef fish assemblages across 4 inshore regions of the Great Barrier Reef Marine Park (GBRMP), Australia, over 12-14 years (2007-2021). Each region had a unique disturbance history, in conjunction with long-term changes in physical and habitat variables. Phases of recovery were apparent in the years between disturbance events at all locations, but these were not long enough to prevent substantial declines in reef fish density (by 33%-72%) and species richness (by 41%-75%) throughout the study period. The main drivers of change in fish assemblages varied among regions; however, the most rapid changes followed cyclone and flood events. Limited recovery periods resulted in temporal shifts in fish species composition from typically coral-associated to algae-associated. Most trophic groups declined in density except farmers, grazers, omnivores and parrotfish. No-take marine reserves (NTMRs) had small and inconsistent effects on total fish assemblages, but delivered benefits for fishery-targeted piscivores. Our findings suggest that coral reef responses to local stressors and cumulative escalating climate change impacts are highly variable at regional scales, and that small NTMRs are unlikely to mitigate the impacts of increasingly frequent climatic disturbances. Nearshore coral reefs worldwide are high-value habitats that are either already degraded or vulnerable to degradation and the loss of important fish groups. Global efforts to reduce greenhouse gas emissions must be coupled with effective local management that can support the functioning and adaptive capacity of coral reefs.

Benthic and fish community composition on mesophotic reefs in Grand Cayman.

Mesophotic Coral Ecosystems (MCEs) represent unique ecological habitats that range from 30 to 150 m deep, harbouring phylogenetically distinct species and offering refuge for many taxa during times of environmental stress. Yet owing to inaccessibility of ecosystems at these depths, most MCEs remain unexplored, with quantifications of ecological communities in these habitats lacking across many regions. Here, using open- and closed-circuit technical diving, we quantified benthic and fish community composition at four mesophotic reef sites (45 m depth) in Grand Cayman. We show significant differences in benthic community composition over a small spatial scale driven by disparate coverage of sponges, crustose coralline algae, and sand/rubble, yet consistent patterns of macroalgal dominance representing >50% coverage at each site and low hard coral cover at an average of 2.4%. Reef fish species richness, biomass, and density was consistent across sites, however the relative contribution of individual species to community composition differed significantly. Macrocarnivores were found to be the dominant contributors to biomass, with invertivores the most speciose, and omnivores and planktivores at the highest densities, consistent with previous descriptions of mesophotic fish assemblages in other regions. Similarly, the low hard coral cover and high macroalgae and sponge cover of the benthic communities also appear ecologically similar to several described mesophotic reefs yet is not uniform across the Caribbean. The ecological organisation of Grand Cayman's MCEs may result from a variety of factors such as isolation from other major land masses, geology, local geography, and anthropogenic activity at both the local and global scale and highlight the importance of continued exploration and documentation of MCE communities.

Irrelationship between live coral cover and reef fish: an interim study of marine habitat dynamic on Mandangin Islands

Most coral reef ecosystems with high coverage of living coral would escalate the reef fish abundance and species richness as one of the correlatable communities to the coral reef. However, reef fish could only utilize one of the coral reef ecosystems to provide to the reef fish community that still withstand and adapt to those conditions. This study aims to assess the coral reef ecosystem quality on Mandangin Islands and the correlation between the benthic substrate to the reef fish structure. Coral reef ecosystem was assessed using Line Intercept Transect and Underwater Visual Census. A linear model or regression analysis was built to identify the key predictors driving factor in the ecosystem. Rock, Sand, and Rubble are the highest benthic substrate around Mandangin Islands. Reef fish have a high abundance along the observation site with exhaustive trophic level, high major functional group, broad bodied size with high abundance small to moderate bodied-size. Rock has a positive correlation to reef fish abundance; Sand has possibilities to escalate species richness, whereas live coral negatively correlates to reef fish. Historically Mandangin Islands contained a healthy coral reef ecosystem that degraded after years, yet reef fish withstand and adapt to the Mandangin Islands’ degraded coral reef ecosystems. Rock is coral that loses several of its function, especially as direct nourishment. This study showed that reef fish should be considered as one of the primary data to strengthen the decision-making of Integrated Coastal Management and Oil Spill Contingency Plans by the Oil and Gas Company.

Spatio-temporal distribution of juvenile fish species in Guadeloupean reefs (Lesser Antilles)

In the life cycle of coral reef fishes, recruitment is a key process which permit the renewal and the replenishment of adult fish populations. Numerous biotic and abiotic factors can influence recruitment, such as the quality of habitat, fish density and fish predation, and reef fish larvae can disperse over long distances. As a result, the distribution of fish juveniles among different habitats can significantly vary spatially and temporally. Here, we described spatio-temporal variation in juvenile fish distribution at the scale of Guadeloupe Island (Caribbean). Visual surveys of fish juveniles were conducted monthly for one year, on six sites representing three types of reef present in Guadeloupe (barrier reef, fringing reef, and patch reef). Significant differences were found in the abundance and species richness of juvenile reef fish depending on the geographical location, and reef type of the studied site. Significant differences were found in abundance between months of the year, and in species richness between the two seasons of the Caribbean region. Species composition differed between sites function of the month of observation, and it was established that the most abundant species at each site were responsible for the spatio-temporal variation observed in the juvenile fish assemblage. Overall, the distribution of juvenile reef fish in Guadeloupe varies both spatially (depending on geographical position and reef type) and temporally (depending on the season). These variations certainly have a strong influence on the stock of adult fish found all around the island of Guadeloupe.

Patterns of reef fish taxonomic and functional diversity in the Eastern Tropical Pacific

A core challenge in ecology is identifying the factors that determine species distribution and functional diversity of species assemblages. Reef fish are the most diverse group of vertebrates, form taxonomically rich and functionally diverse communities and represent a key source of food for humans. We examine regional distribution patterns of reef fish species richness and functional diversity and investigate how these are determined by historical, biogeographic, energetic, and anthropogenic factors. We compiled data from 3,312 underwater visual censuses performed at 122 locations comprising rocky and coral reefs along the Eastern Tropical Pacific (ETP). We used generalized linear mixed‐effects models (GLMMs) implemented in a Bayesian framework to investigate whether distance from quaternary refugia, distance from mainland, shelf area, primary productivity, sea surface temperature (SST), human population gravity, and conservation status influence reef fish species richness and functional diversity in the ETP. Species richness and functional richness (FRic) peaked towards the center of the ETP and our null model suggests that FRic followed a spatial pattern that would be predicted by species richness. Additionally, functional evenness (FEve) was highest at higher latitudes whereas functional dispersion (FDis) was homogeneous throughout the ETP. Species richness was negatively influenced by shelf area and distance from mainland, but positively influenced by SST and conservation status. FEve was influenced by human population gravity and FDis by shelf area. Reef fish species richness and functional diversity in the ETP exhibited a strong division within the region mainly mediated by SST and human population gravity. Our results also suggest that dominant species within small shelf areas share more common traits than dominant species in large areas. This study uncovers previously unknown regional patterns of reef fish functional diversity and provides new insights into how historical, biogeographic, energetic, and anthropogenic factors influence complementary biodiversity facets.

Global analysis of reef ecosystem services reveals synergies, trade-offs and bundles

Millions of people around the world depend on the ecosystem services produced by rocky and coral reef ecosystems, including nutrition, aesthetic value, and coastal protection. Rocky and coral reefs also contribute to critical global and regional processes through the cycling of nitrogen, phosphorus, and carbon. The increased stress experienced by reefs in the Anthropocene threatens their ability to provide vital ecosystem services. This study investigates bundles of ecosystem services, ecosystem services that occur together, to identify trade-offs and synergies among services produced by coral reefs. To do this, we bring together estimates of seven ecosystem services: productivity, nitrogen cycling, phosphorus cycling, inorganic carbon cycling, aesthetic value, nutritional value, and coastal protection. We use correlations analysis to understand trade-offs and synergies between these seven ecosystem services and cluster analysis to identify clusters of reefs with distinct suites of ecosystem services, or ecosystem service bundles. Our analysis reveals (1) synergies and trade-offs among the seven ecosystem services, and (2) three distinct clusters of reefs, which differ on the basis of their overall and relative delivery of ecosystem services. Differences in service production among the clusters appear to be linked to differences in key ecological traits, including total reef fish biomass and species richness. Similar applications of ecosystem service bundles analysis in other marine and coastal systems could result in improved understanding of the spatial distributions and relationships between marine ecosystem services, which is a key input to marine policy.

Assembly rules of coral reef fish communities along the depth gradient

Coral reefs are home to some of the most studied ecological assemblages on the planet. However, differences in large-scale assembly rules have never been studied using empirical quantitative data stratified along the depth gradient of reefs. Consequently, little is known about the small- and regional-scale effects of depth on coral reef assemblages. Using a large dataset of underwater surveys, we observed that the influence of classic biogeographic drivers on the species richness of coral reef fishes changes significantly with depth, shaping distinct assemblages governed by different rules in mesophotic coral ecosystems. We show that a general pattern of decreased taxonomic and functional richness of reef fish assemblages with depth results from convergent filtering of species composition and trophic strategies on deeper reefs across ocean basins and that at smaller scales deep-reef communities are less influenced by regional factors than shallower reefs.

The reef fish assemblage of a coral reef system in the southwestern Gulf of Mexico

Reef fish species richness of the Veracruz Reef System National Park (VRSNP) in the SW Gulf of Mexico is well known. However, the knowledge of the assemblage structure and its spatial variability in the reef ecosystem is quite limited. For that purpose, 5 field surveys (2012-2015) were performed, using the stationary visual census method, at 10 selected reefs. The most important findings were: 116 reef species were recorded. Average total reef fish density (2.31 Ind/m2) is similar to the records for the Caribbean reefs in the 20th century. The top 5 most abundant species were: Chromis multilineata, Ocyurus chrysurus, Abudefduf saxatilis, Stegastes leucostictus, and Elacatinus jarocho. We found evidence of a spatial distribution pattern with 3 well-defined groups of reefs: (1) those near the city of Veracruz, (2) those near the outlet of the Jamapa River, and (3) those farther from the city. Higher fish densities are associated to both high hermatypic coral and low crustose coralline algae bottom covers. The assemblage structure of reef fishes is different at distinct geomorphological reef zones. As expected, with some differences in the species abundance order, the assemblage structure of reef fishes is similar at all coral reefs in the Gulf of Mexico.

Greater resilience of reef fish assemblages in a no-take reserve compared to multi-use areas of the Gulf of California

Conservation strategies, such as the establishment of Marine Protected Areas (MPAs), aim to safeguard biodiversity and to promote resilience of ecosystems by increasing their capacity to maintain key functions and processes following disturbance. However, the extent to which ecosystems in MPAs exhibit resilience remains debated. To address this question, we evaluated changes in reef fish species and functional diversity over time in relation to environmental and anthropogenic disturbances at multiple locations in the Gulf of California, Mexico. From 2005 to 2017, we assessed reef fish species richness and abundance in three MPAs: one no-take marine reserve (Cabo Pulmo) and two multi-use marine protected areas (MUMPAs: Espíritu Santo and Loreto). To examine change in functional diversity and composition, we calculated three functional diversity indices – functional richness, functional dispersion and functional originality – using six biological traits (size, mobility, period of activity, gregariousness, water column position, and diet). Species richness, density and functional diversity were maintained over time (resilience) in the no-take marine reserve. In contrast, MUMPAs showed temporal decline in species richness, which translated into decreases in functional richness and increases in functional dispersion. These differences were also observed at the species level: in Cabo Pulmo, only two ‘loser’ species declined in density, while Espíritu Santo and Loreto showed declines of 12 and 17 species, respectively. The two MUMPAs also shared 9 of the total 22 ‘loser’ species, which are generally abundant and common in the Gulf of California. Density declines were attributed to the combined effect of environmental (sea surface temperature and Chlorophyll-a anomalies) and anthropogenic (fishing, tourism and coastal population density) disturbances. Given the regional decline and the ecological importance of dominant species, long-term decreases in their populations can profoundly modify processes and reef ecosystem services in this region. Thus, local management strategies should be implemented to try to reverse the observed recent decline in fish diversity in MUMPAs.

Depth and habitat are important drivers of abundance for predatory reef fish off Pemba Island, Tanzania

Coral reefs across the world face significant threats from fishing and climate change, which tends to be most acute in shallower waters. This is the case off Pemba Island, Tanzania, yet the effects of these anthropogenic stressors on the distribution and abundance of economically and ecologically important predatory reef fish, including how they vary with depth and habitat type, is poorly understood. Thus, we deployed 79 baited remote underwater videos (BRUVs) in variable water depths and habitats off Pemba Island, and modeled the effects of depth and habitat on abundance of predatory reef fish. Predatory reef fish types/taxa were significantly predicted by depth and habitat types. Habitats in relatively deeper waters and dominated by hard and soft corals hosted high species richness and abundance of predatory reef fish types/taxa compared to mixed sandy and rubble habitats. The findings add to the growing evidence that deep waters around coral reefs are important habitats for predatory reef fish. Thus, careful management, through effective area and species protection measures, is needed to prevent further depletion of predatory reef-associated fish populations and to conserve this biologically important area.

Assessment of reef fish and benthic cover of the North and South Dar es Salaam Marine Reserves system before the 2016 El Niño

The status of reef fish density, diversity, species richness, biomass and coral cover was evaluated by comparing the conditions in two Dar es Salaam Marine Reserves (DMRs); the North Dar es Salaam Marine Reserve (NDMR; gazetted in 1975), and the South Dar es Salaam Marine Reserves (SDMRs; gazetted in 2007), before the 2016 El Niño. A 10 m line-intercept transect was used to characterize benthic cover and a 50 m belt transect was used to assess reef fish population status. Sampling occurred between August 2014 and April 2015. The results showed that fish biomass in the (NDMRs) was 2.7 times higher than that in the (SDMRs) and live hard coral cover was 3 times higher. Higher reef fish density, biomass, diversity, species richness and live hard coral cover were revealed before 2016 El Niño in NDMRs as compared to the SDMRs. Differences in status are linked to differences in time of gazetting and level of effective management in the marine protected areas (MPAs), where NDMRs has a General Management Plan (GMP) while SDMRs does not, and the differences in management are likely to have contributed to the differences in fish biomass and coral cover.

Diversity of Coral Reef Fishes in the Western Indian Ocean: Implications for Conservation

Communities of coral reef fishes are changing due to global warming and overfishing. To understand these changes and inform conservation, knowledge of species diversity and distributions is needed. The western Indian Ocean (WIO) contains the second highest coral reef biodiversity hotspot globally, yet a detailed analysis of the diversity of coral reef fishes is lacking. This study developed a timed visual census method and recorded 356 species from 19 families across four countries in the WIO to examine patterns in species diversity. Species richness and composition differed most between the island countries of Madagascar and Comoros and both these locations differed from locations in Tanzania and Mozambique which were similar. These three regional groupings helped define WIO ecoregions for conservation planning. The highest species richness was found in Tanzania and Mozambique, and the lowest and most different species composition was found in Comoros. Biogeography explains these differences with naturally lower species diversity expected from the small, oceanic, and isolated islands of Comoros. Present day ocean currents maintain these diversity patterns and help explain the species composition in northeast Madagascar. Species distributions were driven by 46 of the 356 species; these provide guidance on important species for ongoing monitoring. The results provide a benchmark for testing future changes in reef fish species richness.

Global tropical reef fish richness could decline by around half if corals are lost.

Reef fishes are a treasured part of marine biodiversity, and also provide needed protein for many millions of people. Although most reef fishes might survive projected increases in ocean temperatures, corals are less tolerant. A few fish species strictly depend on corals for food and shelter, suggesting that coral extinctions could lead to some secondary fish extinctions. However, secondary extinctions could extend far beyond those few coral-dependent species. Furthermore, it is yet unknown how such fish declines might vary around the world. Current coral mass mortalities led us to ask how fish communities would respond to coral loss within and across oceans. We mapped 6964 coral-reef-fish species and 119 coral genera, and then regressed reef-fish species richness against coral generic richness at the 1° scale (after controlling for biogeographic factors that drive species diversification). Consistent with small-scale studies, statistical extrapolations suggested that local fish richness across the globe would be around half its current value in a hypothetical world without coral, leading to more areas with low or intermediate fish species richness and fewer fish diversity hotspots.

Reef-Fish Abundance, Biomass, and Biodiversity Inside and Outside No-Take Marine Zones in the Florida Keys National Marine Sanctuary: 1999–2018

Observations from the Reef Visual Census program in the Florida Keys National Marine Sanctuary (FKNMS) between 1999 and 2018 were used as a US Marine Biodiversity Observation Network case study to assess whether differences in biodiversity metrics (abundance, biomass, richness, Simpson diversity, and functional diversity) occurred across regions with different habitat types (high-relief, linear, and patch reefs), protection levels (no-take and unprotected zones), and types of protected zones. Protected areas had higher reef-fish biomass compared to unprotected areas at the beginning of the observation period, but these metrics decreased over time. We did not detect an effect of size of no-take marine zones, but rather found that large (18.7 km2) and small (average of 0.85 km2) areas had similar reef-fish abundance, biomass, and diversity indices. High-relief reef habitats had the greatest reef-fish abundance (20%–30%) and species richness (~20%), and nearly twice the biomass of other habitat strata, but biomass decreased 20%–30% in linear and patch reefs after 2007. Although high-relief reefs are important for biodiversity conservation and restoration, policies should address the decline in fish abundance, biomass, and diversity observed throughout the FKNMS. Monitoring should be sustained to support policies and respond to changing conditions related to climate change and resource use.

The Value of Habitat Complexity and Diversity of Reef Fish Species in Sangiang Island, Bima Regency, West Nusa Tenggra

Coral reef ecosystems in the marine environment have a vital role, especially in providing habitat for the diversity of commercial and non-commercial fish species. This study aims to assess the species richness of coral reef fish based on the complexity of the habitat of Sangiang Island, Bima Regency. The data collection method used Underwater Visual Census on the belt transect, and the habitat complexity value is determined by the chain intercept transect method. Data analysis used Shannon-Wiener Index Diversity (H '), Abundance (Ki), and Habitat complexity (C). Next is a simple regression analysis between habitat complexity as the independent variable and fish abundance as the dependent variable. In this study, 106 species were found and covering 24 families. The three fish families, Pomacentridae, Labridae, and Lutjanidae, are the most dominant of the other families. Meanwhile, the diversity index ranged from 1.874-2.753 with an average value of ± SD 2.35 ± 0.317, and the abundance value ranged from 0.774-2.528 individuals/m2 with an average value of ± SD 1.505 individuals / m2 ± 0.745. Furthermore, the analysis showed that hábitate complexity had a significant effect on fish abundance. The coefficient of determination (R2) of 80% can explain the relationship of habitat complexity to fish abundance in the study location. This study concludes that coral reef habitat complexity is a determining factor for the level of fish diversity and abundance in the study area. Therefore, the protection of coral habitat is a strategy for the protection of coral reef fish resources.

Biophysical and anthropogenic influences on the status of Tonga's coral reefs and reef fish fishery.

Despite increasing threats to Tonga’s coral reefs from stressors that are both local (e.g. overfishing and pollution) and global (e.g. climate change), there is yet to be a systematic assessment of the status of the country’s coral reef ecosystem and reef fish fishery stocks. Here, we provide a national ecological assessment of Tonga’s coral reefs and reef fish fishery using ecological survey data from 375 sites throughout Tonga’s three main island groups (Ha’apai, Tongatapu and Vava’u), represented by seven key metrics of reef health and fish resource status. Boosted regression tree analysis was used to assess and describe the relative importance of 11 socio-environmental variables associated with these key metrics of reef condition. Mean live coral cover across Tonga was 18%, and showed a strong increase from north to south correlated with declining sea surface temperature, as well as with increasing distance from each provincial capital. Tongatapu, the southernmost island group, had 2.5 times greater coral cover than the northernmost group, Vava’u (24.9% and 10.4% respectively). Reef fish species richness and density were comparable throughout Tongatapu and the middle island group, Ha’apai (~35 species/transect and ~2500 fish/km2), but were significantly lower in Vava’u (~24 species/transect and ~1700 fish/km2). Spatial patterns in the reef fish assemblage were primarily influenced by habitat-associated variables (slope, structural complexity, and hard coral cover). The biomass of target reef fish was greatest in Ha’apai (~820 kg/ha) and lowest in Vava’u (~340 kg/ha), and was negatively associated with higher human influence and fishing activity. Overall mean reef fish biomass values suggest that Tonga’s reef fish fishery can be classified as moderately to heavily exploited, with 64% of sites having less than 500 kg/ha. This study provides critical baseline ecological information for Tonga’s coral reefs that will: (1) facilitate ongoing management and research; and (2) enable accurate reporting on conservation targets locally and internationally.

Isolation promotes abundance and species richness of fishes recruiting to coral reef patches

Habitat area and fragmentation are recognised as important factors that influence population size, community structure and extinction risk. Abundance and species richness universally increase with habitat area. However, the effects of different aspects of habitat fragmentation, including variation in patch size, number and isolation are often not distinguished from each other or the overall effects of habitat amount. Here we experimentally tested predictions concerning the effects of isolation on abundance, species richness and community structure of coral reef fishes colonising patch reefs by constructing clusters of patches of the same number and size, but manipulating reef spacing. Hexagonal clusters of 7 experimental patch reefs (6 edge and 1 central) with 3 levels of isolation (1 m, 5 m, and 15 m spacing) were established at Kavieng, Papua New Guinea and colonisation was recorded after 6 weeks in 2014. We also deployed video cameras to test whether isolation affected the activity of transient predatory fishes. As predicted, isolation had a positive effect on both mean abundance and species richness at both the cluster and patch scale. The cumulative abundance and species richness exhibited linear increases in relation to habitat area within clusters (from 1 to 7 patch reefs), but the slope increased with the degree of isolation. There was some evidence that transient predators remained longer and were more successful when patches were close together, which may explain the lower abundance and richness of juvenile fish assemblages on more aggregated patch reefs. This study demonstrates that while habitat amount is fundamentally important, isolation has significant effects that will need to be distinguished from other aspects of fragmentation when examining the processes structuring reef fish communities.

The condition of economical important coral reef fishes in eastern and western small outer island Indonesia

More than three months of cumulative comprehensive studied we conducted to evaluate coral reef fishes composition in Eastern Indonesia Region (Liki Island) and Western Indonesia Region (Natuna Island) of small outer Island (SOI) Indonesia. There is a fundamental problem in the ecological function of the coral reef ecosystem and the potential of economically important reef fishes in small outer Island Indonesia. Several obstructions become an essential problem, including the location of SOI, which is far from the mainland with a lack of surveillance and monitoring; consequently, the coral ecosystem and its coral reef fishes are threatened. Overfishing and destructive fishing are the major problems reported in several locations on the outermost island. Both anthropogenic stressors cause degraded coral ecosystems and give the loss specific species of marine species, especially in economically important coral reef fishes that primary target for fisheries. The latest and continuous time series data is essential as necessary information to arrange the appropriate and sustainable policies in Small outer islands, especially in protected the ecosystem from ecological extinction. The main goal of our study is to evaluate the potential of economic coral reef fishes with analysis of two families of fundamental economic and targeted fisheries: groupers (Serranidae) and snapper (Lutjanidae) in eastern and western small outer island Indonesia. The data were collected in each six site location in both eastern and western region SOI using Underwater Visual Census (UVC) technique. Four parameters, including species richness, abundance, biomass, and indices of economic coral reef fishes (Shannon, Evenness, Simpson, and ENS), were compared between the eastern region (Liki) to the Western region (Natuna) with Kruskal-Wallis non-parametric statistical analysis and internal Pairwise Wilcoxon analysis. The eastern region (Liki) recorded higher fish richness, abundance, and biomass than the western region (Natuna) (p< 0.05). Comparisons with ecological indices shown in the eastern region SOI (Liki) had a more diverse economic important coral reef fishes than western region SOI (Natuna). Understanding the composition of economically important coral reef fish in SOI will reveal more about the condition of the ecological function of the coral ecosystem and their vulnerability to future changes.

Community management yields positive impacts for coastal fisheries resources and biodiversity conservation

AbstractCombining 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.

Changes in reef fish assemblages following multiple bleaching events in the world’s warmest sea (Kish Island, the Persian Gulf)

Climate change affects the ecology of reef fish through changing their habitat, community and their feeding and territorial behavior. The corals and their associated reef fish in the Persian Gulf as the world’s warmest sea suffer from the increasing frequency and severity of mass bleaching events. Yet, the effects of climate-induced coral bleaching events on reef fish in this sea are poorly understood. Using a time series fish count data, this study evaluated the response of reef fish to multiple severe coral bleaching events in Kish Island located in the central Persian Gulf. The results showed a decline in species richness and diversity of reef fish after bleaching events which reduced mean coral cover by 85% following the 2007 bleaching event and by 95% following the 2017 bleaching event. Besides a drop in the number of fish species, the total density, and density of trophic groups changed as the results of coral loss. The variation in density of different trophic groups indicated an overall increase in the abundance of benthic invertebrate feeders (21.2–136.3%), omnivores (32.4–163.4%) and plankton feeders (218.5–488%). In contrast, the abundance of coral polyp feeders (−6.9 to −50%) and piscivores (−4.9 to −38.9%) significantly decreased after bleaching events. The density of herbivorous fish significantly increased by 97.1% after the bleaching event in 2007 and decreased by 10.5% after the bleaching event in 2017. In the present study, we demonstrated how the impact of the multiple bleaching events on associated reef fish assemblages sustained for about 6 years after the disturbance. These results have significant implications for our understanding of the response of reef fish to global warming and highlight the growing concern about the future of coral reef ecosystems and their associated reef fish in the region as the warmest sea in the world.