Reef Fish Diversity Research Articles

Opening of an MPA to fishing: Natural variations in the structure of a coral reef fish assemblage obscure changes due to fishing

Marine Protected Areas (MPAs) are known to enhance diversity, density and biomass of coral reef fishes and to modify the size and trophic structures of these fish assemblages. Opening to fishing has the opposite effects, but on a much shorter time scale. The present study compares the evolution of the fish assemblages of two adjacent reef zones, both initially MPAs, one of them being afterwards opened to fishing. The study was conducted on Aboré Reef, a New Caledonian barrier reef (SW Pacific) which constituted a 148 km 2 marine protected area, of which 69 km 2 are within the lagoon. Two surveys of a coral reef fish assemblage, using underwater visual censuses, were performed, the first one was conducted in July 1993 following 5 years of protection from fishing, the second one was conducted in July 1995; part of the reef having been opened to fishing activity in September 1993. This study examined the effects of two factors on these fish communities: time (1993 vs. 1995) and zone (reefs protected from fishing vs. unprotected reefs); the interaction of these two factors indicating an effect of either protection or opening to fishing. Diversity (species/transect), density and biomass were tested for all species together (377 species), then according to diet, size and commercial use. There was a significant decrease over time of most values in both fished and unfished areas, the decrease being greater in the zone opened to fishing. The magnitude of decrease over time was within the range of known time variations from other studies in New Caledonia and other Pacific locations. However, this decrease was so large that it prevented the detection of effects linked to protection. Only some minor effects could be detected for 16 species with no specific pattern according to diet, size or use. The density and biomass of species of low commercial value were also affected by opening to fishing. Relative changes in diversity could be better detected than relative changes in density or biomass. This study demonstrates that on a short-term basis (2 years), natural variations can be of larger magnitude than changes that may be induced by management options, especially when fishing pressure is not very high.

Reef Fish Inventory of Juan De Nova's Natural Park (Western Indian Ocean)

This paper constitutes the first study on reef fish communities at Juan de Nova, one of the Eparses Islands in the Mozambique Channel. These remote islands, with no permanent habitation, except a small military base, represent sites which experience minimal direct human influence. Sampling was firstly done by underwater visual observations, using SCUBA diving gear, at 31 stations distributed equally over the coral reef, between depths ranging from 0-15 m, and secondly, by using an anaesthetic in littoral rockpools. A total of 299 species belonging to 55 families were recorded. Nearly half of the observed species belong to five main families: Labridae (41 species), Pomacentridae (28 species), Acanthuridae (24 species), Serranidae (22 species), and Chaetodontidae (18 species). Among the reported species, 73% are carnivores, 16% herbivores and 11% omnivores. Some families are well represented, especially the carnivores such as sharks (Carcharhinidae, 6 species), the groupers (Serranidae, 20 species) and the snappers (Lutjanidae, 10 species), which are common at nearly every station sampled. The presence of these carnivorous species could be related to the absence of fishing pressure in the area. However, some species known to be common in the area seemed rare (e.g. Chaetodon trifascialis, Dascyllus carneus, Labroides bicolour) or entirely absent (Pseudanthias cooperi, Cephalopholis miniata, Chaetodon unimaculatus, Plectroglyphidodon johnstonianus and Lepidozygus tapeinosoma). From a biogeographic point of view, this study revealed a fairly diverse reef fish community for such a small, isolated island, located on the westward extreme (~ 45°E, 15°S) of the Indo-Pacific. The absence or the paucity of certain species and/or families could be the consequence of the 1998 massive coral bleaching. There is a need for long-term studies in order to better understand the resilience of coral reef communities to environmental disturbances.. Keywords: reef fishes, diversity, Eparses Islands, natural reserve, western Indian Ocean, biogeography, massive bleaching West Indian Ocean Journal of Marine Science Vol. 4 (2) 2005: pp. 145-162

Predictability of reef fish diversity and abundance using remote sensing data in Diego Garcia (Chagos Archipelago)

The diversity, abundance and distribution of reef fish are related to heterogeneity and physical complexity of benthic habitat. However, the field effort required to evaluate these aspects of the benthos in situ, at the scale of entire reefscapes, is greatly constrained by logistical and resource limitations. With moderate ground truthing, both substratum type and seabed topography are amenable to monitoring using satellite data. Here, remote sensing imagery was used to resolve the bathymetry and benthic character of a reef system in Diego Garcia (British Indian Ocean Territory). Replicate fish counts were made at seven measurement stations across the study area using visual census. Monte Carlo simulation revealed that species richness and abundance of several guilds and size groupings of reef fish appraised in situ were correlated with the satellite-derived seabed parameters over areas of seafloor as large as 5,030 m2. The study suggests that satellite remote sensing is capable of predicting habitat complexity at a scale relevant to fish. Furthermore, as larger size classes of fish were better predicted with the satellite habitat complexity data, this technique could be used to predict fish stocks and identify potential sites for marine protected areas where intensive field surveys are not practical.

Devil in the Details: High-resolution Dietary Analysis Contradicts a Basic Assumption of Reef-Fish Diversity Models

Reef-fish diversity models, unlike general diversity-gradient hypotheses, assume food specialization by reef fishes is too low to influence community structure. This assumption may be an artifact of low taxonomic resolution in studies of fish diets. I performed detailed dietary analyses on adults of eight small, cryptic, diurnal fish species from the spur-and-groove habitat outside Kaneohe Bay, Oahu, Hawaii to test whether dietary specialization may facilitate high species richness in reef fish communities. Mean dietary overlap (0.179) among these fishes is similar to overlap in communities thought to be structured by fine-scale food specialization. Dietary studies with high taxonomic resolution indicate a significant decrease in food overlap among fishes as latitude decreases. These results, along with the generally recognized increase in prey diversity toward the tropics, are consistent with diversity-gradient hypotheses and suggest that food specialization allows the local coexistence of many fish species on coral reefs. Local relative abundances of reef fishes may be influenced by prey availability. The densities of five of six fish species were related to densities of important prey. Food choice and availability may influence richness and relative abundances, respectively, in reef fishes, and reef-fish communities may be structured in the same manner as other tropical communities.

Baseline assessment of the reef fish assemblage from Cagarras Archipelago, Rio de Janeiro, southeastern Brazil

The extensive Brazilian coast comprises diverse reef fish communities. Here, we report a pioneer study on the reef fish community composition of the Cagarras Archipelago. This rocky reef system consists of a small group of coastal islands 5 km south off Ipanema Beach, Rio de Janeiro city, Brazil. A relatively diverse and disturbed fish community (99 species from 39 families) was found in this archipelago. Two different visual census techniques were utilized and a large difference was observed in the number of species compared to other Brazilian reef sites. Trophic structure and biogeographical affinities are discussed. The absence of some reef fish species, mainly top predators, suggests severe environmental impact in this area and exhorts the Brazilian authorities to create a marine protected area. Results obtained in this study will serve to future environmental studies in Cagarras.

Extreme genetic diversity and temporal rather than spatial partitioning in a widely distributed coral reef fish

Mitochondrial control region (HVR-1) sequences were used to identify patterns of genetic structure and diversity in Naso vlamingii, a widespread coral reef fish with a long evolutionary history. We examined 113 individuals from eight locations across the Indo-Pacific Ocean. Our aims were to determine the spatial scale at which population partitioning occurred and then to evaluate the extent to which either vicariance and/or dispersal events have shaped the population structure of N. vlamingii. The analysis produced several unexpected findings. Firstly, the genetic structure of this species was temporal rather than spatial. Secondly, there was no evidence of a barrier to dispersal throughout the vast distribution range. Apparently larvae of this species traverse vicariance barriers that inhibit inter-oceanic migration of other widespread reef fish taxa. Thirdly, an unusual life history and long evolutionary history was associated with a population structure that was unique amongst coral reef fishes in terms of the magnitude and pattern of genetic diversity (haplotype diversity, h = 1.0 and nucleotide diversity π = 13.6%). In addition to these unique characteristics, there was no evidence of isolation by distance (r = 0.458, R2 = 0.210, P = 0.078) as has also been shown for some other widespread reef species. However, some reductions in gene flow were observed among and within Ocean basins [Indian–Pacific analysis of molecular variance (AMOVA), Φst = 0.0766, P < 0.05; West Indian–East Indian–Pacific AMOVA Φst = 0.079, P < 0.05]. These findings are contrasted with recent studies of coral reef fishes that imply a greater degree of spatial structuring in coral reef fish populations than would be expected from the dispersive nature of their life cycles. We conclude that increased taxon sampling of coral reef fishes for phylogeographic analysis will provide an extended view of the ecological and evolutionary processes shaping coral reef fish diversity at both ends of the life history spectrum.

Assessing Genetic Diversity of Brazilian Reef Fishes by Chromosomal and DNA Markers

Little is known on genetics of Brazilian coral reef fish and most of this information is limited to chromosome characterization of major representative species. The diploid chromosome number in marine fish varies from 2n= 22-26 to 2n = 240-260. Despite of this apparent diversity, most studied marine species have a diploid complement with 48 acrocentric chromosomes. This latter trend is mostly observed among Perciformes, an important major taxon of coral reef fishes. Studies in the families Pomacentridae, Pomacanthidae and Chaetodontidae, for example, have shown a common karyotype pattern entirely formed by 48 uniarmed chromosomes. However, rare numerical and structural chromosome polymorphisms and cryptic chromosome rearrangements involving heterochromatin segments and/or nucleolar organizing sites have been reported among such fishes. Although new chromosome forms can contribute to the establishment of genetically isolated populations, their role in reef fish speciation at marine realm still is an open question. More recently, genomic DNA analyses using RAPD and microsatellites, and sequencing and RFLP of mitochondrial DNA have increasingly been used in Atlantic reef fish species. Genetic homogeneity over wide geographical ranges has been reported for different fish groups, in contrast to several cases of population substructuring related to environmental constraints or evolutionary history. Amazonas outflow and upwelling on the Southeastern coast of Brazil are believed to be strong barriers to dispersal of some reef species. Moreover, it is suggested that the pattern of speciation and population structure at South Atlantic is quite distinctive from Pacific Ocean, even when comparing closely related taxa. Further genetic studies are strongly encouraged in Brazilian reef fishes in order to provide a reliable scenario of the genetic structure in this important and diverse fish group.

Effects of fishing and protection on Brazilian reef fishes

The vast Brazilian coast harbors unique and diverse reef fish communities. Unfortunately, relatively little is known about the impact of fishing on these fish species, and few management or conservation efforts are being made to protect them. Here, we examine the effect of different levels of protection on the composition, abundance, and size structure of reef fish species along a 2500 km portion of the Brazilian coastline, noting in particular the relative abundance of endemics and the effect of protection on these species. Pairwise comparisons of sites with different protection status (more versus less protected) were used to determine the potential responses of reef fishes to the establishment of marine protected areas. Highly targeted species (top predators and large herbivores) were significantly more abundant and larger in size within sites with a higher degree of protection, indicating that they benefit from protection, while lightly fished and unfished species were not. These results are consistent with past work documenting the responses of species to protection. Here, we use our results in particular to suggest strategies and provide expectations for managing and protecting Brazilian reef fisheries. Because this biogeographic province lies entirely within the jurisdiction of a single nation, there may be unique and significant opportunities to effectively manage and conserve these fish species.

Reef fish diversity at Aldabra Atoll, Seychelles, during the five years following the 1998 coral bleaching event

Quantitative surveys of fish-species diversity were undertaken at 10 m and 20 m water depth on the outer reef at Aldabra Atoll, southern Seychelles, between November 1999 and May 2003. No significant changes in total fish-species diversity, numbers of families represented by these species, or numbers of pomacentrid or chaetodontid species were seen, contrary to fish-diversity changes seen on coral bleaching-impacted reefs elsewhere. The lack of additional anthropogenic pressures at remote Aldabara may make this system, and others like it, more tolerant of bleaching-related population changes.

Composition, abundance and diversity of coral reef fishes at two sites in Mochima National Park, Venezuela

The composition, abundance and diversity of fishes in two reef patches located in Mochima National Park (Venezuela) were analyzed from January 2001 to January 2002. Monthly captures were made in deep zones. A total of 829 individuals were found and 67 species were recorded, of which 25 were common to both localities. In Cautaro, 547 specimens, belonging to 51 species and 24 families, were caught. The most abundant families were Scaridae (39.31%), Chaetodontidae (17.18%), Pomacentridae (13.89%), and Haemulidae (11.71%). Diversity ranged from 0.68 to 3.21 bits/ind, evenness from 0.29 to 0.98, and species richness from 0.68 to 2.24. Five of the species were permanent residents, seven were recurrent visitors and thirty-nine were occasional visitors. The most abundant species were Sparisoma aurofrenatum (39.31%), Chaetodon capistratus (16.27%) and Abudefduf saxatilis (13.89%). In Manzanillo, 282 specimens, belonging to 41 species and 21 families, were caught. The most numerous families were Sparidae (23.76%), Haemulidae (16.31%), and Chaetodontidae (11.70%). Diversity ranged from 1.00 to 3.22 bits/ind, evenness from 0.5 to 1, and species richness from 0.95 to 2.50. Three of the species were permanent residents, eight were recurrent visitors and thirty were occasional visitors. The most abundant species were Diplodus argenteus (23.76%), C. capistratus (11.70%), and Haemulon flavolineatum (11.34%). The higher species diversity found in Cautaro than in Manzanillo could be due to the higher structural complexity of the former.

Patterns and processes in reef fish diversity

A central aim of ecology is to explain the heterogeneous distribution of biodiversity on earth. As expectations of diversity loss grow, this understanding is also critical for effective management and conservation. Although explanations for biodiversity patterns are still a matter for intense debate, they have often been considered to be scale-dependent. At large geographical scales, biogeographers have suggested that variation in species richness results from factors such as area, temperature, environmental stability, and geological processes, among many others. From the species pools generated by these large-scale processes, community ecologists have suggested that local-scale assembly of communities is achieved through processes such as competition, predation, recruitment, disturbances and immigration. Here we analyse hypotheses on speciation and dispersal for reef fish from the Indian and Pacific oceans and show how dispersal from a major centre of origination can simultaneously account for both large-scale gradients in species richness and the structure of local communities.

The cleaner wrasse, Labroides dimidiatus, is a key organism for reef fish diversity at Ras Mohammed National Park, Egypt

Summary In marine cleaning symbioses, small fish or shrimps remove ectoparasites and other material from cooperating ‘client’ fish. Until now, there has been conflicting evidence with respect to the importance of cleaning for client health and in particular with respect to the impact of cleaning organisms on local fish diversity. Data are provided on the impact of the cleaner wrasse Labroides dimidiatus on reef fish distribution at Ras Mohammed National Park, Egypt. During four field seasons, I regularly sampled fish species composition in 46 reef patches. Natural fluctuations in cleaner fish presence or absence at these reef patches allowed me to assess how this variable correlates with reef fish diversity. In addition, cleaner fish were removed experimentally from some reef patches and added at others to test whether the presence or absence of cleaner fish causes changes in fish diversity. Both cleaner fish disappearance and cleaner fish removal had no immediate effects on fish abundance, i.e. within the first few weeks. A significant decline in fish diversity was only detectable after 4–20 months. In contrast, cleaner immigration or experimental addition led to a significant increase in fish diversity within the first few weeks. Generally, effects were most pronounced for client species that visit reef patches and soon move off again, and less pronounced (but still significant) for resident clients that do not move between reef patches. Surprisingly, the presence or absence of cleaner fish also affected the distribution of resident fish that hardly ever interact with them. This study demonstrates that cleaner fish are a key organism for local reef fish diversity.

Erosion vs. Recovery of Coral Reefs after 1998 El Niño: Chagos Reefs, Indian Ocean

Three years after most corals died on the central Indian Ocean reefs of Chagos, erosion and recovery were studied to 30 m depth. Mortality was near-total to 15 m deep in northern atolls, and to > 35 m in central and southern atolls. Some reef surfaces have 'dropped' 1.5 m due to the loss of dense coral thickets. Coral bioerosion is substantial, reducing 3-D reef 'structure' and forming unconsolidated rubble. Juvenile corals are abundant, though mostly on eroding or unstable substrates, and are of less robust species. Reef fish abundance and diversity at 15 m depth remains high; species dependent on corals have diminished, while some herbivores and detritivores have increased. A new sea surface temperature (SST) data set shows that mean SST has risen 0.65 degree C since 1950. The critical SST causing the mortality in Chagos was 29.9 degrees C.

Community Structure of Reef Fish in Several Habitats of a Rocky Reef in the Gulf of California

Abstract. To explore the relationships between habitat structure, distribution, and diversity of conspicuous reef fish, surveys were made in 1994, 1995 and 1998 at Los Islotes, a rocky islet located north of Bahía de La Paz, B.C.S., México. The site was divided into six zones, which presented different habitats: rhodoliths, walls, big boulders, small boulders and black coral. Some physical descriptors for the substrate were determined: depth, rugosity, number and size of rocks, and the percent coverage of several types of sessile invertebrates. Number of species and abundances were determined by visual transects. Two main seasons were distinguished, and the number of species was different between seasons and among zones. Four fish groups were identified based on the frequency and abundance of species. These fish groups presented similar proportions in each zone. Although most species recorded at Los Islotes were found in all the studied habitats, their densities varied significantly between habitats, suggesting groups of ‘representative’ species. Correlation analysis showed relationships between physical characteristics and the ‘representative’ species, that can be explained by the natural history of each species, including feeding behavior and shelter requirements.

Visual census methods underestimate density and diversity of cryptic reef fishes

The diversity and density of small, benthic reef fishes were estimated using visual census and enclosed rotenone stations. Visual census underestimated the number of species present and the density of common species by up to 91%.

Visual census methods underestimate density and diversity of cryptic reef fishes

Visual census methods underestimate density and diversity of cryptic reef fishes

Habitat interdependence in coral reef ecosystems: a case study in a Mexican Caribbean reef

The structural patterns and trophodynamics of the different fish species in the reef complex of Palancar-Chunchakaab, located in the South of Cozumel Island, Mexican Caribbean, were studied. A total of 166 species were identified for the whole reef complex. The analysis of 19,636 recorded and 2291 fish collected allowed the populations to be characterized in terms of diversity, distribution, abundance, dominant species and habitat-fish interactions. Using these parameters, three well defined reef-fish communities were described in relation to three zones: (1) Thalassia zone (THZ), (2) Lagoon (LA) and (3) Shelf-Edge Reef (SER). These communities included 64 species (39% of the total number) that were restricted to a single zone, . The remaining 61% consisted of migratory species that interacted between the defined zones (interdependence of habitat): (1) THZ–LA, (2) THZ–LA–SER, and (3) LA–SER. Diversity was highest in the rainy season in SER (H′ n=3.3). Analysis of distribution and frequency of 42 of the recorded species revealed that for 25%, life cycle and THZ–SER were closely related. The remaining 75% were more associated with SER or THZ and they used these habitats for feeding, breeding and/or protection. In THZ, >70% of the total number of species were juveniles; in LA, 40% were preadults–adults; and in SER 80% were adults. The obvious interdependence between habitats suggested a distinct use of the resources by means of migration patterns. By decreasing the order of importance, the major diet types can be ranked as follows: (1) type I carnivores, mainly active by day, preying on small organisms such as crustaceans, polychaetes, mollusks, echinoderms; (2) type II carnivores, nocturnal species consuming larger crustaceans and fish; (3) strict piscivores species; (4) herbivores species; (5) planktivores species; (6) omnivores species; and (7) sessile invertebrate browsers. With the exception of SER, 14%–44% of the type II invertebrate feeders were restricted to the three defined habitats. Of the migratory species, the large invertebrate feeders were the dominant group (21%–41%). The present study suggests that the variation of species diversity patterns and trophic structure are associated with sequential habitat use according to the life cycle. This type of study allowed us to compare the diversity and trophic community of reef fish of the same system and to recognize the energetic interdependence that exists between the habitats.

Habitat interdependence in coral reef ecosystems: a case study in a Mexican Caribbean reef

Abstract The structural patterns and trophodynamics of the different fish species in the reef complex of Palancar-Chunchakaab, located in the South of Cozumel Island, Mexican Caribbean, were studied. A total of 166 species were identified for the whole reef complex. The analysis of 19,636 recorded and 2291 fish collected allowed the populations to be characterized in terms of diversity, distribution, abundance, dominant species and habitat-fish interactions. Using these parameters, three well defined reef-fish communities were described in relation to three zones: (1) Thalassia zone (THZ), (2) Lagoon (LA) and (3) Shelf-Edge Reef (SER). These communities included 64 species (39% of the total number) that were restricted to a single zone,. The remaining 61% consisted of migratory species that interacted between the defined zones (interdependence of habitat): (1) THZ–LA, (2) THZ–LA–SER, and (3) LA–SER. Diversity was highest in the rainy season in SER (H′ n = 3.3). Analysis of distribution and frequency of 42 of the recorded species revealed that for 25%, life cycle and THZ–SER were closely related. The remaining 75% were more associated with SER or THZ and they used these habitats for feeding, breeding and/or protection. In THZ, &amp;gt; 70% of the total number of species were juveniles; in LA, 40% were preadults–adults; and in SER 80% were adults. The obvious interdependence between habitats suggested a distinct use of the resources by means of migration patterns. By decreasing the order of importance, the major diet types can be ranked as follows: (1) type I carnivores, mainly active by day, preying on small organisms such as crustaceans, polychaetes, mollusks, echinoderms; (2) type II carnivores, nocturnal species consuming larger crustaceans and fish; (3) strict piscivores species; (4) herbivores species; (5) planktivores species; (6) omnivores species; and (7) sessile invertebrate browsers. With the exception of SER, 14%–44% of the type II invertebrate feeders were restricted to the three defined habitats. Of the migratory species, the large invertebrate feeders were the dominant group (21%–41%). The present study suggests that the variation of species diversity patterns and trophic structure are associated with sequential habitat use according to the life cycle. This type of study allowed us to compare the diversity and trophic community of reef fish of the same system and to recognize the energetic interdependence that exists between the habitats.

Patterns of species diversity in the gastrointestinal helminths of a coral reef fish, Epinephelus merra (Serranidae), from French Polynesia and the South Pacific Ocean

Large-scale patterns of species diversity in the gastrointestinal helminth faunas of the coral reef fish Epinephelus merra (Serranidae) were investigated in French Polynesia and the South Pacific Ocean. The richer barrier reef community in French Polynesia supported richer parasite communities in E. merra than that on the fringing reef. While parasite communities among fish from the same archipelago were similar, differences in potential host species and the distance between archipelagos may have contributed to a qualitative difference in parasite communities between archipelagos. Digenean community diversity in coral reef fishes was greater in the western South Pacific, following similar patterns in free-living species. However, overall species diversity of camallanid nematodes of coral reef fishes does not appear to have been similarly affected.

Impacts of predator depletion by fishing on the biomass and diversity of non-target reef fish communities

An understanding of the indirect effects of fishing on predator-prey relationships is required for the development of valid multispecies yield models for reef fisheries and for determining the factors governing fish community structure at larger scales. We used an underwater visual census technique to examine the indirect effects of fishing on the biomass and diversity (species richness) of reef fishes in a series of ten traditional Fijian fishing grounds (qoliqoli) subject to a range of fishing intensities. All members of the families Chaetodontidae (butterflyfishes), Labridae (wrasses), Lutjanidae (snappers), Mullidae (goatfishes), Scaridae (parrotfishes) and the sub-family Epinephelinae (groupers and coral trout) which could be reliably identified were censused. Each species censused was assigned to one of three trophic groups: herbivore, invertebrate feeder or piscivore. The biomass of all piscivorous fishes and of large (>30 cm) piscivorous fishes differed significantly between qoliqoli and was significantly correlated with fishing intensity. However, the biomass of piscivorous fishes was not correlated with the biomass or diversity of their potential prey (which were not targeted by the fishery). This suggested that the indirect effects of fishing did not have an important bearing on fish diversity or biomass and that predation by the target species did not play an important role in structuring these Fijian reef fish communities. The results contrast with those from a number of studies at smaller scales and provided further indications that the structure of reef fish communities is not governed by a single dominant process, but by a range of processes which operate on different scales in different circumstances.