Abundance Of Coral Reef Fishes Research Articles

Environmental change and connectivity drive coral reef fish abundance in the Western Indian Ocean

Abstract Worldwide, coral reefs are facing risk from climate change. The Western Indian Ocean (WIO) harbours about 16% of global coral reefs with highly reef-dependent local communities. Coastal protection and food security depend on effective conservation management, which requires understanding species abundances. Here, we explore how fish group distribution and abundance across the WIO, categorized by their trophic function, are explained by oceanographic connectivity, sea surface temperature (SST), and chlorophyll a. We designed a proportional oceanographic connectivity metric describing the relative strength of connectivity between all WIO coral reefs and each survey site. We created statistical models for four trophic groups: grazers and detritivores, herbivorous excavators, corallivores, and primary piscivores across 51 sites in the WIO. We show that SST and chlorophyll a are strong predictors of all trophic fish groups and that the proportional oceanographic connectivity metric improved the model predictions significantly for grazers and detritivores and excavators. For excavators, peak abundances were predicted at medium connectivity, and for grazers and detritivores, at low and medium connectivity, suggesting that larvae dispersal predominates at a local scale. Decision making should include connectivity for efficient conservation area prioritization, for which our proportional oceanographic connectivity metric is a valid and useful parameter.

Environmental DNA biomonitoring reveals seasonal patterns in coral reef fish community structure

Coral reef fish populations are declining due to multiple factors including habitat destruction, overfishing, and climate change. While these can include seasonal impact, seasonal changes can also be a confounding factor, so that seasonal monitoring is essential for detecting true temporal changes in fish community abundance and composition. However, seasonal monitoring is rarely implemented. The aim of this study was to detect the seasonal patterns of coral reef fish community structure around Tidung Kecil Island, Indonesia, using eDNA metabarcoding (eDNA) and underwater visual census (UVC). The UVC identified 32 species belonging to 10 families in the rainy season and 29 species belonging to 7 families in the dry seasons. The eDNA metabarcoding identified 209 species belonging to 56 families and 27 species belonging to 17 families in the rainy and dry seasons, respectively. Based on eDNA metabarcoding data, coral reef fish abundance and community composition differed significantly between seasons (Mann Whitney, p < 0.01), while the UVC method did not detect these seasonal differences (Mann Whitney, p > 0.05). UVC and eDNA data both showed a predominance of omnivorous fishes in the rainy season and carnivorous fishes in the dry season. Ecological indices did not differ significantly between seasons for the two used methods, although the species making the highest contributions to the similarity (SIMPER) analysis differed between methods. Overall, this study confirms the premise that eDNA metabarcoding can be an effective tool for monitoring seasonal variation in coral reef fish communities.

Diversity of reef fish on Lembeh Island as an indicator of the coral reef health condition

Lembeh Strait in North Sulawesi is one of the areas included in the world’s coral triangle. Coral reef structures provide a habitat for reef fish. Herbivorous and invertivorous fish were essential to determine the direction of coral reef succession. This study aims to examine the health of coral reefs based on the presence of reef fish. Observations were conducted on January 16-19, 2019, with a total of 22 observation points. Observation of reef fish communities using the underwater visual census (UVCs) and belt transect method. At the observation site, it was found that there were 260 species of reef fish. The resilience of coral reefs based on the presence of reef fish has a high value on the parameters of the abundance of herbivorous fish, taxonomic diversity, and abundance of coral reef fish.

Global decline in capacity of coral reefs to provide ecosystem services

Global decline in capacity of coral reefs to provide ecosystem services

The Correlation Between Coral Cover and The Associated Reef Fishes Abundance in Enggano Island Bengkulu

The coral reef is the habitat for more than a million marine species. The damage of the coral reef could decrease associated marine biodiversity, and the coral reef fishes are one of the groups impacted by the coral reef destruction. This study aimed to measure the coral coverage, to estimate the abundance of coral fishes, and to determine the correlation between coral coverage and abundance of coral reef fishes in Enggano Island, Bengkulu. The line intercept transect method was used by applying 25 m length transects to measure the coral cover in 12 sampling stations. The visual census method was implemented to count the presence of coral reef fishes around the transect line. The correlation between coral coverage and abundance of coral reef fishes was estimated using the multiple-linear-regression method. The results revealed that the coral coverage in Enggano Island varies from 99.6%-6.6%. The highest coverage was observed in station one at the leeward of Dua Island, whereas the lowest was found in station nine at Kahabi. The depth that measured 21 m could cause low coral coverage in condition. The substratum at this depth receives low sunlight intensity; thus, photosynthesis could not function efficiently. The highest coral reef fish abundance estimated at 603 ind/125 m2 was found in station 12 at Berhau, whereas the lowest at 8 ind/125m2 was in station eight at Kahabi. The analysis showed a positive but considerably a weak correlation between coral coverage and abundance of coral reef fishes with an r-value of 0.61 and the determination coefficient of 61.00%.

Size-specific recolonization success by coral-dwelling damselfishes moderates resilience to habitat loss

Increasing degradation of coral reef ecosystems and specifically, loss of corals is causing significant and widespread declines in the abundance of coral reef fishes, but the proximate cause(s) of these declines are largely unknown. Here, we examine specific responses to host coral mortality for three species of coral-dwelling damselfishes (Dascyllus aruanus, D. reticulatus, and Pomacentrus moluccensis), explicitly testing whether these fishes can successfully move and recolonize nearby coral hosts. Responses of fishes to localized coral loss was studied during population irruptions of coral feeding crown-of-thorns starfish, where starfish consumed 29 (34%) out of 85 coral colonies, of which 25 (86%) were occupied by coral-dwelling damselfishes. Damselfishes were not tagged or individually recognizable, but changes in the colonization of different coral hosts was assessed by carefully assessing the number and size of fishes on every available coral colony. Most damselfishes (> 90%) vacated dead coral hosts within 5 days, and either disappeared entirely (presumed dead) or relocated to nearby coral hosts. Displaced fishes only ever colonized corals already occupied by other coral-dwelling damselfishes (mostly conspecifics) and colonization success was strongly size-dependent. Despite movement of damselfishes to surviving corals, the local abundance of coral-dependent damselfishes declined in approximate accordance with the proportional loss of coral habitat. These results suggest that even if alternative coral hosts are locally abundant, there are significant biological constraints on movement of coral-dwelling damselfishes and recolonization of alternative coral habitats, such that localized persistence of habitat patches during moderate or patchy disturbances do not necessarily provide resilience against overall habitat loss.

Declining abundance of coral reef fish in a World-Heritage-listed marine park

One of the most robust metrics for assessing the effectiveness of protected areas is the temporal trend in the abundance of the species they are designed to protect. We surveyed coral-reef fish and living hard coral in and adjacent to a sanctuary zone (SZ: where all forms of fishing are prohibited) in the World Heritage-listed Ningaloo Marine Park during a 10-year period. There were generally more individuals and greater biomass of many fish taxa (especially emperors and parrotfish) in the SZ than the adjacent recreation zone (RZ: where recreational fishing is allowed) — so log response ratios of abundance were usually positive in each year. However, despite this, there was an overall decrease in both SZ and RZ in absolute abundance of some taxa by up to 22% per year, including taxa that are explicitly targeted (emperors) by fishers and taxa that are neither targeted nor frequently captured (most wrasses and butterflyfish). A concomitant decline in the abundance (measured as percentage cover) of living hard coral of 1–7% per year is a plausible explanation for the declining abundance of butterflyfish, but declines in emperors might be more plausibly due to fishing. Our study highlights that information on temporal trends in absolute abundance is needed to assess whether the goals of protected areas are being met: in our study, patterns in absolute abundance across ten years of surveys revealed trends that simple ratios of abundance did not.

Relationship between coral reef ecosystem and coral fish communities in Unggeh Island Central Tapanuli Regency

Coral reef ecosystems in Unggeh Island waters have recently declined in quality due to natural factors and human activities. The declining quality can affect the biota of the coral reef ecosystem, such as coral reef fish. Coral reef fish belong to the groups of fish whose lives are associated with the coral reef ecosystem environment. This study aims to determine the abundance and diversity of coral reef fish and the relationship between abundance of coral reef fish and the percentage of coral cover in Unggeh Island Waters, Badiri District, Central Tapanuli Regency, North Sumatra. This research was conducted in December 2017 and April 2018. The method used to observe the coral was Underwater Photo Transect (UPT) method. And the method used to observe the coral reef fish was Underwater Visual Census (UVC) method. To determine the relationship between coral cover and coral reef fish was by using a simple linear regression equation. The results showed that the relationship of coral cover with coral reef fish was in the correlation value (R) of 0.418.

Influence of management status on the coral reef fish communities in Ujung Kulon National Park, Banten

Ujung Kulon National Park (TNUK) employs a management with the zonation system established to maintain the sustainability of resources, one of them are coral reef fish. This study aimed to identify the influence of management status on coral reef fish. Field observations were conducted on 14-22 October 2017 in Ujung Kulon using underwater visual census method, by recording the fish found in observation transects. The coral reef fish most frequently found in Core Zone was Caesionidae, while in The Marine Protection Zone is Acanthuridae. The Core Zone has higher species richness, and more abundance of coral reef fish than the Marine Protection Zone, although only species richness parameter shows a significant difference based on statistical tests. The management status that regulates the activities in each zoning has an impact on the coral reef ecosystem, including coral reef fish communities in it. Coral reef fish in the Core Zone have more diverse species than the Marine Protection Zone, because the coral reefs in the Core Zone are more preserved than the Marine Protection Zone.

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean.

AimUnderstanding the drivers of the structure of coral reef fish assemblages is vital for their future conservation. Quantifying the separate roles of natural drivers from the increasing influence of anthropogenic factors, such as fishing and climate change, is a key component of this understanding. It follows that the intrinsic role of historical biogeographical and geomorphological factors must be accounted for when trying to understand the effects of contemporary disturbances such as fishing.LocationComoros, Madagascar, Mozambique and Tanzania, Western Indian Ocean (WIO).MethodsWe modeled patterns in the density and biomass of an assemblage of reef‐associated fish species from 11 families, and their association with 16 biophysical variables.ResultsCanonical analysis of principal coordinates revealed strong country affiliations of reef fish assemblages and distance‐based linear modeling confirmed geographic location and reef geomorphology were the most significant correlates, explaining 32% of the observed variation in fish assemblage structure. Another 6%–8% of variation was explained by productivity gradients (chl_a), and reef exposure or slope. Where spatial effects were not significant between mainland continental locations, fishing effects became evident explaining 6% of the variation in data. No correlation with live coral was detected. Only 37 species, predominantly lower trophic level taxa, were significant in explaining differences in assemblages between sites.Main ConclusionsSpatial and geomorphological histories remain a major influence on the structure of reef fish assemblages in the WIO. Reef geomorphology was closely linked to standing biomass, with “ocean‐exposed” fringing reefs supporting high average biomass of ~1,000 kg/ha, while “lagoon‐exposed fringing” reefs and “inner seas patch complex” reefs yielded substantially less at ~500kg/ha. Further, the results indicate the influence of benthic communities on fish assemblages is scale dependent. Such insights will be pivotal for managers seeking to balance long‐term sustainability of artisanal reef fisheries with conservation of coral reef systems.

Keanekaragaman dan Biomassa Ikan Karang serta Keterkaitannya dengan Tutupan Karang Hidup di Perairan Manggis, Kabupaten Karangasem, Bali

The existence of coral reef fish is closely related to the availability of coral reef resource as a habitat. Coral reef fish is a biota that has a fascination with a variety of color patterns and fascinating. Differences in coral cover conditions will affect the abundance of coral reef fish, especially those with strong linkages to living corals. This research was conducted in June - August 2017 by using line intercept transect (LIT) method for coral cover percentage and visual census method for biodiversity and biomass of coral reef fish with 3 research stations in Manggis waters, Karangasem. From the research results, it shows that the diversity index ranged between 2.54 - 2.70 which means the diversity of coral reef fish in the medium category and the stability of the community is in the medium. Furthermore, total biomass of coral reef fish ranged between 186,17 - 1692,08 kg / ha. The results stated that the percentage of live coral cover in Manggis waters ranged from 3.83% to 12.44% which means that live coral cover is categorized as bad. A very strong positive correlation between living coral conditions and coral reef fish biomass was 92.42%. Meanwhile, the relationship between living coral conditions and the diversity of coral reef fish had a strong positive correlation of 65.4%. The diversity of coral reef fish in waters is not only caused by live coral cover; however, it is caused by coral reef ecosystems that are associated in the bottom of the waters.

Habitat change mediates the response of coral reef fish populations to terrestrial run-off

Coastal fish populations are typically threatened by multiple human activities, including fishing pressure and run-off of terrestrial pollution. Linking multiple threats to their impacts on fish populations is challenging because the threats may influence a species directly, or indirectly, via its habitats and its interactions with other species. Here we examine spatial variation in abundance of coral reef fish across gradients of fishing pressure and turbidity in Fiji. We explicitly account for multiple pathways of influence to test the alternative hypotheses that (1) habitat moderates predation by providing shelter, so habitat loss only affects prey fish populations if there are abundant predators, (2) habitat change co-drives biomass of both prey and predator functional groups. We examined responses of 7 fish functional groups and found that habitat change co-drives both predator and prey responses to turbidity. Abundances of all functional groups were associated with changes in habitat cover; however, the responses of their habitats to turbidity were mixed. Planktivore and piscivore abundance were lower in areas of high turbidity, because cover of their preferred habitats was lower. Invertivore, browser and grazer abundance did not change strongly over the turbidity gradient, because different components of their habitats exhibited both increases and decreases with turbidity. The effects of turbidity on fish populations were minor in areas where fish populations were already depleted by fishing. These findings suggest that terrestrial run-off modifies the composition of reef fish communities indirectly by affecting the benthic habitats that reef fish use.

Habitat bleaching disrupts threat responses and persistence in anemonefish

Climate-induced habitat bleaching is linked to dramatic declines in diversity and abundance of coral reef fish; however, mechanisms underlying these declines are poorly understood. Here, we used in situ studies to demonstrate that bleaching can influence persistence of reef fish by affecting behaviours, including responses to a potential predation threat. When encountering the predatory rock cod Cephalophalis cyanostigma, anemonefish Amphiprion akindynos occupying healthy unbleached host anemones Heteractis crispa respond by feeding less and spending more time within the anemone tentacles. When the host anemone was experimentally bleached, these visual risk responses were compromised: A. akindynos continued to feed and did not seek shelter. The impaired behavioural response may prove detrimental to anemonefish populations as abundance levels of fish on bleached anemones was reduced by 60% within 3 d, which may have been the result of increased predation. Our data illustrate how climate-induced habitat degradation can drive declines of reef fish by potentially altering outcomes of predator–prey interactions.

Depth and reef profile: effects on the distribution and abundance of coral reef fishes

The physical and biological structure of coral reef habitats vary in relation to depth and the profile of the reef, from vertical walls to gentle slopes. The differing roles of depth and reef profile on fish distribution and abundance, and the role of habitat structure in explaining these patterns, have received little attention. Here these effects were distinguished by surveying reef fish species and benthic habitat in quadrats on three aspects (shelf, slope and wall) at each of two depths (5 m and 15 m) in Kimbe Bay, Papua New Guinea. Both depth and reef profile accounted for considerable variation in reef fish communities. Species diversity and richness was highest on the shelf profile and lowest on the wall profile at 5 m. Whereas, at 15 m the opposite was true with the wall profile being the most diverse and species rich profile and the shelf being the least. Wall habitats were the most different from the other two profiles in terms of community structure. Depth had a greater influence on fish communities on slope and shelf habitats, with shallow slopes and shelfs similar to one another, and deep slopes and shelfs also similar. Some rare species, such as Chromis delta and Pictichromis paccagnellae, were restricted only to walls. The relative effects of depth and reef profile on benthic habitat structure were similar to the fish communities, with the sponge and encrusting coral dominated wall habitats being the most dissimilar to the other aspects, with clear depth patterns also. There was a significant correlation between the fish communities present and the habitat availability at the depths and on the reef profiles studied. The correlation was best explained by sand, branching coral, encrusting coral, massive coral and rubble. Depth and reef profile had a significant interaction, which suggests that, clearly, both depth and profile are important factors affecting reef fish communities. Although, benthic habitat appears to only partially explain these patterns.

Non-linear effects of invasive lionfish density on native coral-reef fish communities

One of the major goals of invasion biology is predicting the effects of invaders on native species, which is often accomplished by linearly scaling-up per-capita effects with invader abundance. However, the relationship between invader density and their ecological impact is poorly understood, and it is likely that the effects of invasive species scale non-linearly with increasing invader density. The Pacific red lionfish (Pterois volitans) is an invasive predator that has reached high abundances throughout the tropical and sub-tropical western Atlantic, Caribbean, and Gulf of Mexico. A single lionfish can have extremely large effects on native reef-fish communities, yet the relationship between lionfish density and their ecological effects is not well known. I manipulated juvenile lionfish densities on small patch reefs in the Bahamas and monitored the subsequent effects on native coral-reef fish abundance, biomass, richness, evenness, composite diversity, and community structure over 7 weeks. Native fish abundance and biomass decreased non-linearly with increasing lionfish density, with the largest drops in abundance and biomass at low lionfish densities and their effects leveling off at high densities. Lionfish density also significantly affected richness and community structure, but these effects could not be clearly classified as either linear or non-linear. Evenness and composite diversity were not significantly affected by lionfish density. Given that the effects of lionfish on native fish abundance and biomass level-off at high lionfish densities, it appears important to remove all lionfish from small patch reefs to have the biggest influence on conserving the native community.

Limited contemporary gene flow and high self‐replenishment drives peripheral isolation in an endemic coral reef fish

Extensive ongoing degradation of coral reef habitats worldwide has lead to declines in abundance of coral reef fishes and local extinction of some species. Those most vulnerable are ecological specialists and endemic species. Determining connectivity between locations is vital to understanding recovery and long-term persistence of these species following local extinction. This study explored population connectivity in the ecologically-specialized endemic three-striped butterflyfish (Chaetodon tricinctus) using mt and msatDNA (nuclear microsatellites) to distinguish evolutionary versus contemporary gene flow, estimate self-replenishment and measure genetic diversity among locations at the remote Australian offshore coral reefs of Middleton Reef (MR), Elizabeth Reef (ER), Lord Howe Island (LHI), and Norfolk Island (NI). Mt and msatDNA suggested genetic differentiation of the most peripheral location (NI) from the remaining three locations (MR, ER, LHI). Despite high levels of mtDNA gene flow, there is limited msatDNA gene flow with evidence of high levels of self-replenishment (≥76%) at all four locations. Taken together, this suggests prolonged population recovery times following population declines. The peripheral population (NI) is most vulnerable to local extinction due to its relative isolation, extreme levels of self-replenishment (95%), and low contemporary abundance.

Role of prey availability in microhabitat preferences of juvenile coral trout (Plectropomus: Serranidae)

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.

Predicting spatially explicit coral reef fish abundance, richness and Shannon–Weaver index from habitat characteristics

The assessment of biodiversity in coral reefs requires the application of geographic information systems (GIS), remote sensing and analytical tools in order to make cost-effective spatially explicit predictions of biodiversity over large geographic areas. Here we present a spatially explicit prediction for coral reef fish diversity index, as well as habitat classification according to reef fish diversity index values in Chinchorro Bank Biosphere Reserve, one of the most important plain/atoll type reef systems in the Caribbean. We have used extensive ecological data on depth, fish and habitat characteristics to perform such prediction. Fish species assemblages and different biotic variables of benthic organisms were characterized using visual censuses and video-transects, respectively at 119 sampling stations. The information was integrated in a GIS, along with satellite imagery (LANSDAT 7 ETM+) and a digital bathymetric model. From the recorded data and a hierarchical classification procedure, we obtained nine different classes of habitats. We used a generalized regression analysis and spatial prediction methodology to create predictive maps (GIS layers) of the different reef benthic components, and a second modeling run produced predictive maps of coral reef fish diversity index. Predictive accuracy of the diversity index map presented a good correlation coefficient (r = 0.87), with maximum diversity index values en reefscapes composed of aggregation of coral colonies with seagrass beds. The implementation of our application was successful for the prediction of fish diversity hot spots and surrogate habitats.

Contrasting effects of habitat loss and fragmentation on coral-associated reef fishes

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.

Using underwater cameras to assess the effects of snorkeler and SCUBA diver presence on coral reef fish abundance, family richness, and species composition

The results of underwater visual fish censuses (UVC) could be affected by fish changing their behavior in response to the snorkeler or diver conducting the survey. We used an underwater video camera to assess how fish abundance, family richness, and community composition were affected by the presence of snorkelers (n = 12) and self-contained underwater breathing apparatus (SCUBA) divers (n = 6) on a coral reef in Thailand. The total number of families, abundance of some fish families, and overall species composition showed significant differences before and during snorkeling disturbances. We did not detect significant and consistent changes to these parameters in the presence of a SCUBA diver; however, this could be a result of lower statistical power. We suggest that the use of a stationary video camera may help cross-check data that is collected through UVC to assess the true family composition and document the presence of rare and easily disturbed species.