Kenyan coral reef lagoon fish: effects of fishing,substrate complexity,and sea urchins

Population density, number of species, diversity, and species-area relationships of fish species in eight common coral reef-associated families were studied in three marine parks receiving total protection from fishing, four sites with unregulated fishing, and one reef which recently received protection from fishing (referred to as a transition reef). Data on coral cover, reef topographic complexity, and sea urchin abundance were collected and correlated with fish abundance and species richness. The most striking result of this survey is a consistent and large reduction in the population density and species richness of 5 families (surgeonfish, triggerfish, butterflyfish, angelfish, and parrotfish). Poor recovery of parrotfish in the transition reef, relative to other fish families, is interpreted as evidence for competitive exclusion of parrotfish by sea urchins. Reef substrate complexity is significantly associated with fish abundance and diversity, but data suggest different responses for protected versus fished reefs, protected reefs having higher species richness and numbers of individuals than unprotected reefs for the same reef complexity. Sea urchin abundance is negatively associated with numbers of fish and fish species but the interrelationship between sea urchins, substrate complexity, coral cover, and management make it difficult to attribute a set percent of variance to each factor-although fishing versus no fishing appears to be the strongest variable in predicting numbers of individuals and species of fish, and their community similarity. Localized species extirpation is evident for many species on fished reefs (for the sampled area of 1.0 ha). Fifty-two of 110 species found on protected reefs were not found on unprotected reefs.     

Community structure and biogeography of shore fishes in the Gulf of Aqaba,Red Sea

Shore fish community structure off the Jordanian Red Sea coast was determined on fringing coral reefs and in a seagrass-dominated bay at 6 m and 12 m depths. A total of 198 fish species belonging to 121 genera and 43 families was recorded. Labridae and Pomacentridae dominated the ichthyofauna in terms of species richness and Pomacentridae were most abundant. Neither diversity nor species richness was correlated to depth. The abundance of fishes was higher at the deep reef slope, due to schooling planktivorous fishes. At 12 m depth abundance of fishes at the seagrass-dominated site was higher than on the coral reefs. Multivariate analysis demonstrated a strong influence on the fish assemblages by depth and benthic habitat. Fish species richness was positively correlated with hard substrate cover and habitat diversity. Abundance of corallivores was positively linked with live hard coral cover. The assemblages of fishes were different on the shallow reef slope, deep reef slope and seagrass meadows. An analysis of the fish fauna showed that the Gulf of Aqaba harbours a higher species richness than previously reported. The comparison with fish communities on other reefs around the Arabian Peninsula and Indian Ocean supported the recognition of an Arabian subprovince within the Indian Ocean. The affinity of the Arabian Gulf ichthyofauna to the Red Sea is not clear. Received in revised form: 2 November 2001 Electronic Publication     

Relationships between structural complexity,coral traits,and reef fish assemblages

With the ongoing loss of coral cover and the associated flattening of reef architecture, understanding the links between coral habitat and reef fishes is of critical importance. Here, we investigate whether considering coral traits and functional diversity provides new insights into the relationship between structural complexity and reef fish communities, and whether coral traits and community composition can predict structural complexity. Across 157 sites in Seychelles, Maldives, the Chagos Archipelago, and Australia’s Great Barrier Reef, we find that structural complexity and reef zone are the strongest and most consistent predictors of reef fish abundance, biomass, species richness, and trophic structure. However, coral traits, diversity, and life histories provided additional predictive power for models of reef fish assemblages, and were key drivers of structural complexity. Our findings highlight that reef complexity relies on living corals—with different traits and life histories—continuing to build carbonate skeletons, and that these nuanced relationships between coral assemblages and habitat complexity can affect the structure of reef fish assemblages. Seascape-level estimates of structural complexity are rapid and cost effective with important implications for the structure and function of fish assemblages, and should be incorporated into monitoring programs.     

Maintenance of fish diversity on disturbed coral reefs

Habitat perturbations play a major role in shaping community structure; however, the elements of disturbance-related habitat change that affect diversity are not always apparent. This study examined the effects of habitat disturbances on species richness of coral reef fish assemblages using annual surveys of habitat and 210 fish species from 10 reefs on the Great Barrier Reef (GBR). Over a period of 11 years, major disturbances, including localised outbreaks of crown-of-thorns sea star (Acanthaster planci), severe storms or coral bleaching, resulted in coral decline of 46–96% in all the 10 reefs. Despite declines in coral cover, structural complexity of the reef framework was retained on five and species richness of coral reef fishes maintained on nine of the disturbed reefs. Extensive loss of coral resulted in localised declines of highly specialised coral-dependent species, but this loss of diversity was more than compensated for by increases in the number of species that feed on the epilithic algal matrix (EAM). A unimodal relationship between areal coral cover and species richness indicated species richness was greatest at approximately 20% coral cover declining by 3–4 species (6–8% of average richness) at higher and lower coral cover. Results revealed that declines in coral cover on reefs may have limited short-term impact on the diversity of coral reef fishes, though there may be fundamental changes in the community structure of fishes.     

Additive partitioning of reef fish diversity variation: a promising marine biodiversity management tool

Additive partitioning was applied to variation in reef fish spatial diversity at Isla Isabel National Park, Nayarit state, Mexico, and to identify the environmental and spatial variables that best explains it. Analyses included expected and observed species curves, rare species analysis, additive partitioning of alpha- and beta-diversity, and canonical redundancy analysis. A total of 10,517 individuals were recorded from 75 species and 33 reef fish families, representing 85% of expected richness. Species richness beta-diversity was dependent on the site scale, while the alpha-diversity of the Shannon diversity was most significant at the transect scale. Canonical partitioning showed species richness and Shannon diversity was explained by spatially-structured environmental components. Variation in species composition and abundance was explained by a purely environmental component. Therefore, elements of habitat structure (especially corals), topographic complexity, and refuge availability determine fish species diversity. Our results suggest that greater emphasis is required to conserve sites that promote β-diversity, increasing fish spatial diversity. In Isla Isabel, these sites would be mostly those located at eastern and southern of protected sides, where coral reef patches are well represented. The results of this multi-scale analysis are valuable and useful as an addition and complement to the holistic management strategies implemented at Isla Isabel.     

The influence of coral reef benthic condition on associated fish assemblages

Accumulative disturbances can erode a coral reef's resilience, often leading to replacement of scleractinian corals by macroalgae or other non-coral organisms. These degraded reef systems have been mostly described based on changes in the composition of the reef benthos, and there is little understanding of how such changes are influenced by, and in turn influence, other components of the reef ecosystem. This study investigated the spatial variation in benthic communities on fringing reefs around the inner Seychelles islands. Specifically, relationships between benthic composition and the underlying substrata, as well as the associated fish assemblages were assessed. High variability in benthic composition was found among reefs, with a gradient from high coral cover (up to 58%) and high structural complexity to high macroalgae cover (up to 95%) and low structural complexity at the extremes. This gradient was associated with declining species richness of fishes, reduced diversity of fish functional groups, and lower abundance of corallivorous fishes. There were no reciprocal increases in herbivorous fish abundances, and relationships with other fish functional groups and total fish abundance were weak. Reefs grouping at the extremes of complex coral habitats or low-complexity macroalgal habitats displayed markedly different fish communities, with only two species of benthic invertebrate feeding fishes in greater abundance in the macroalgal habitat. These results have negative implications for the continuation of many coral reef ecosystem processes and services if more reefs shift to extreme degraded conditions dominated by macroalgae.     

Retention of Habitat Complexity Minimizes Disassembly of Reef Fish Communities following Disturbance: A Large-Scale Natural Experiment

High biodiversity ecosystems are commonly associated with complex habitats. Coral reefs are highly diverse ecosystems, but are under increasing pressure from numerous stressors, many of which reduce live coral cover and habitat complexity with concomitant effects on other organisms such as reef fishes. While previous studies have highlighted the importance of habitat complexity in structuring reef fish communities, they employed gradient or meta-analyses which lacked a controlled experimental design over broad spatial scales to explicitly separate the influence of live coral cover from overall habitat complexity. Here a natural experiment using a long term (20 year), spatially extensive (∼115,000 kms²) dataset from the Great Barrier Reef revealed the fundamental importance of overall habitat complexity for reef fishes. Reductions of both live coral cover and habitat complexity had substantial impacts on fish communities compared to relatively minor impacts after major reductions in coral cover but not habitat complexity. Where habitat complexity was substantially reduced, species abundances broadly declined and a far greater number of fish species were locally extirpated, including economically important fishes. This resulted in decreased species richness and a loss of diversity within functional groups. Our results suggest that the retention of habitat complexity following disturbances can ameliorate the impacts of coral declines on reef fishes, so preserving their capacity to perform important functional roles essential to reef resilience. These results add to a growing body of evidence about the importance of habitat complexity for reef fishes, and represent the first large-scale examination of this question on the Great Barrier Reef.     

The relationship between fish species richness, abundance and habitat complexity in a range of shallow tropical marine habitats

A simple habitat assessment score (HAS) was designed to assess habitat complexity across several different shallow tropical marine habitats including sandy patches, algal beds, seagrass beds and reefs. It measured rugosity, variety of growth forms, height, refuge size categories, percentage live cover and percentage hard substratum. Multiple regression models using HAS variables as predictors accounted for 71 and 22% of the variation in observed species richness and total fish abundance respectively. The two most important predictors of observed species richness were rugosity and variety of growth forms, while height was the most important predictor of total fish abundance. The HAS method worked consistently across a variety of habitat types and the complexity map closely mirrored the map of observed species richness, reflecting the patchy habitat mosaic of shallow tropical marine areas. Stations at the mouth of an enclosed lagoon, however, had a higher number of species than might have been expected judging from the habitat complexity scores. It is possible that this was linked to the preferential settling of pelagic fish larvae in this area as tidal water exchanges between the bay and the reef were funnelled through one small gap. This study highlights the need for fish biodiversity studies to take habitat complexity into account.     

Similar regional effects among local habitats on the structure of tropical reef fish and coral communities

Aim We examined data on corals and reef fishes to determine how particular local habitat types contribute to variation in community structure across regions covering gradients in species richness and how consistent this was over time. Location Great Barrier Reef (GBR), Australia. Methods We compared large‐scale (1300 km), long‐term (11 years) data on fishes and corals that were collected annually at fixed sites in three habitats (inshore, mid‐shelf and outer‐shelf reefs) and six regions (latitudinal sectors) along a gradient of regional species richness in both communities. We used canonical approaches to partition variation in community structure (sites × species abundance data matrices) into components associated with habitat, region and time and Procrustes analyses to assess the degree of concordance between coral and fish community structure. Results Remarkably similar patterns emerged for both fish and coral communities occupying the same sites. Reefs that had similar coral communities also had similar fish communities. The fraction of the community data that could be explained by regional effects, independent of pure habitat effects, was similar in both fish (33%) and coral (36.9%) communities. Pure habitat effects were slightly greater in the fish (31.3%) than in the coral (20.1%) community. Time explained relatively little variation (fish = 7.9%, corals = 9.6%) compared with these two spatial factors. Conclusions Our results indicate either that fish and coral communities were structured in similar ways by processes associated with region, habitat and time, or that the variation in fish community structure tracked variation associated with the coral communities at these sites and thereby reflects an indirect link between the environment and the structure of fish communities mediated by corals. Irrespective of the causes of such commonality, we demonstrate that community structure, not just species richness, can be related to both habitat differences and regional setting simultaneously.     

Effects of coral restoration on fish communities: snapshots of long‐term,multiregional responses and implications for practice

Coral restoration is widely used around the world to address dramatic declines in coral cover; however, very few studies have looked specifically at the temporal response of fish assemblages (i.e. abundance and diversity) to coral restoration. Several critical reef functions and processes are driven by fishes, thereby making their recovery and responses around restoration structures key indicators of success. This study evaluates fish abundance and community composition on restoration plots following 8–12 years of restoration activity, in four locations (two Caribbean and two Indo‐Pacific). Responses were very complex with region‐, site‐, and body size‐specific patterns. Overall, fish abundance only increased in Indo‐Pacific sites where damselfish responded positively to increased coral cover and topographic complexity. Restoration effects on other fish families and particularly on larger bodied reef fish were negative or neutral at all locations. If restoration initiatives are going to substantively improve the condition and recovery of degraded reef fish communities, restoration efforts need to be planned, designed, and monitored based on fish‐specific habitat requirements and locally specific community dynamics.     

Effects of Habitat Connectivity on the Abundance and Species Richness of Coral Reef Fishes: Comparison of an Experimental Habitat Established at a Rocky Reef Flat and at a Sandy Sea Bottom

Coral reef fish assemblages are widely recognized for the coexistence of numerous species, which are likely governed by both coral diversity and substratum complexity. However, since coral reefs provide diverse habitats due to their physical structure and different spatial arrangements of coral, findings obtained from an isolated habitat cannot necessarily be applied to fish assemblages in other habitats (e.g. continuous habitats). The aim of this study, therefore, was to determine by a field experiment whether habitat connectivity (spatial arrangement of coral colonies) affects abundance and species richness of fishes in an Okinawan coral reef. The experiment consisted of transplanted branching coral colonies at a 4m×8m quadrat at both a rocky reef flat and sandy sea bottom. Generally, the abundance of fishes was greater at the sandy sea bottom, especially for three species of pomacentrids, one species of labrids, one species of chaetodontids and two species of apogonids. Species–area curves showed that the species richness of fishes was significantly greater in the quadrat at the sandy sea bottom at 3, 6 and 9 months after the start of the experiment. The rate of increase in abundance of fishes per area was significantly greater in the quadrat at the sandy sea bottom over the study period. The results of rarefaction analyses showed that the rate of increase in species richness per abundance was significantly higher in the quadrat at the sandy sea bottom in the juvenile settlement period, indicating that the magnitude of dominance by particular species was greater at the sandy sea bottom habitat. Our findings suggest that habitat connectivity affects the abundance and species richness of coral reef fishes, i.e. the isolated habitat was significantly more attractive for fishes than was the continuous habitat. Our findings also suggest that the main ecological factors responsible for organization of fish assemblage at a continuous habitat and at an isolated habitat are different.     

Spatial patterns in abundance of a damselfish reflect availability of suitable habitat

For species with metapopulation structures, variation in abundance among patches can arise from variation in the input rate of colonists. For reef fishes, variability in larval supply frequently is invoked as a major determinant of spatial patterns. We examined the extent to which spatial variation in the amount of suitable habitat predicted variation in the abundance of the damselfish Dascyllus aruanus, an abundant planktivore that occupies live, branched coral throughout the Indo-Pacific. Reef surveys established that size, branching structure and location (proximity to sand) of the coral colonies together determined the ”suitability” of microhabitats for different ontogenetic stages of D. aruanus. Once these criteria were known, patterns of habitat use were quantified within lagoons of five Pacific islands. Availability of suitable habitat generally was an excellent predictor of density, and patterns were qualitatively consistent at several spatial scales, including among different lagoons on the same island, among different islands and between the central (French Polynesia and Rarotonga) and western (Great Barrier Reef, Australia) South Pacific. A field experiment that varied the amount of suitable coral among local plots indicated that habitat for settlers accounted for almost all of the spatial variation in the number of D. aruanus that settled at that location, suggesting that spatial patterns of abundance can be established at settlement without spatial variation in larval supply. Surveys of four other species of reef-associated fish revealed that a substantial fraction of their spatial variation in density also was explained by availability of suitable reef habitat, suggesting that habitat may be a prevalent determinant of spatial patterns. The results underscore the critical need to identify accurately the resource requirements of different species and life stages when evaluating causes of spatial variation in abundance of reef fishes. Received: 18 May 1999 / Accepted: 9 January 1999     

Relationships between habitat structure and fish communities on coral

The influence of habitat structure on reef-fish communities at Bar Reef Marine Sanctuary, Sri Lanka, was investigated. The relationship between habitat characteristics and the distribution and abundance of 135 species of fishes was examined on two reef types: coral and sandstone reefs. Results suggested that the reef-fish communities were strongly influenced by various aspects of reef structure. However, relationships between habitat variables and fish communities structure, varied between the two reef types. Fish species diversity was correlated with a number of habitat variables on the sandstone reefs, although structural complexity seemed to play the dominant role. There were no correlations between habitat structure and fish diversity on the coral reefs. Total abundance was not related to any one habitat parameter on either reef type. However, abundances of some species, families and trophic groups were correlated with habitat features. These specific correlations were commonly related to food or shelter availability. For example, coral feeders were correlated with live coral cover, and pomacentrid species, which used branching corals for protection, showed a significant relationship with the density of Acropora colonies. This shows that a summary statistic such as total abundance may hide important information. Effects of habitat structure on the distribution patterns of the fish communities was further investigated using multi-dimensional scaling ordination (MDS) and the RELATE-procedure. With the MDS ordinations for both habitat and fish-community composition it was possible to show that the multivariate pattern between the two ecological components was clearly correlated.     

Community Structure of Fishes and Habitat Complexity on a Tropical Rocky Shore

The relationship between the variables of reef fish community structure (fish richness, fish diversity and total number of fishes) and those of habitat complexity (total surface area, substratum diversity, topographic complexity, number of holes, percent cover of turf algae, zoanthids, millepores, massive corals, bare rock, encrusting calcareous algae, urchins, other sessile organisms and Sargassum) were examined on three different rocky shores (FA, FB and FT) at Arraial do Cabo, a tropical region located on Brazilian southeastern coast (23° S, 42° W). Fish abundance and vertical distribution were assessed by a visual census technique using strip transects. Percentage cover of benthic organisms and other substratum types were calculated by replicated transects using a chain laid down on the substratum. Topographic complexity was determined by the chain link method and number of holes were estimated by direct counts on replicated transects. More than 91 fishes belonging to 37 families were seen in all study sites during one year of visual census effort. FA and FB sites had similar fish community structure and habitat complexity characteristics, while FT showed different habitat characteristics and higher fish diversity and richness, plus total number of fishes. Vertical distribution of fishes along the rocky shores studied seemed to be predictable and was determined by factors such as feeding habits and behavior, availability of refuges and social interactions. The habitat variables that best explained the higher diversity and number of fishes observed in FT site were total surface area of rocky shores and the abundance of benthic sessile invertebrates; these conditions were typical of rocky shores more exposed to wave surge.     

Seasonal trends and fish-habitat associations around Pari Island, Indonesia: setting a baseline for environmental monitoring

Indonesia is the world??s richest country regarding reef fish diversity. Nevertheless, the reef ichthyofauna of the Indonesian Archipelago remains poorly known, primarily due to a lack of sampling. Coral reefs in the Kepulauan Seribu Marine National Park close to the Indonesian capital Jakarta are under threat by many destructive activities that trigger a loss of habitat and species diversity. This communication: (1) describes the reef fish community structure from three distinct reef habitats in the Pari Island group dominated by Acropora branching corals (ACB), foliose corals (CF) and massive corals (CM), using a number of community properties such as numerical abundance, species richness, diversity, and multivariate similarity; (2) examines the temporal variation of the fish community from the three habitats; and (3) discusses possible implications for the monitoring of qualitative changes in coral reef systems on small islands. During this study, a total of 13 536 individual fishes were counted, representing 205 species belonging to 36 families. In terms of species richness, Pomacentridae was the dominant fish family in ACB and CF sites (40?% and 48.6?%, respectively), and Labridae (27.4?%) was the dominant family in the CM plots. The most species-rich habitat was ACB with 125 species (with Amblyglyphidodon curacao as the most characteristic species), followed by CM and CF with 117 (Thalassoma lunare) and 79 species (Pomacentrus alexanderae), respectively. Average Shannon-Wiener diversity (ln basis) ranged from 2.0?C2.9 (ACB), 2.4?C3.1 (CF), and 2.1?C3.0 (CM), with no significant difference between growth forms. Abundance, species richness and diversity showed significant seasonal variability, but the effects differed between habitats. Multivariate analysis of the reef fish community was able to detect significant differences between species composition and diversity of the reef fish community between sites with different coral growth forms at Pari Island, both when based on species abundances and when aggregated according to trophic categories. It thus constitutes a useful tool to detect qualitative differences of the species-rich Indonesian coral reef ecosystems.     

Coral bleaching, reef fish community phase shifts and the resilience of coral reefs

The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5–35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.     

Different Surrounding Landscapes may Result in Different Fish Assemblages in East African Seagrass Beds

Few studies have considered how seagrass fish assemblages are influenced by surrounding habitats. This information is needed for a better understanding of the connectivity between tropical coastal ecosystems. To study the effects of surrounding habitats on the composition, diversity and densities of coral reef fish species on seagrass beds, underwater visual census surveys were carried out in two seagrass habitat types at various locations along the coast of Zanzibar (Tanzania) in the western Indian Ocean. Fish assemblages of seagrass beds in a marine embayment with large areas of mangroves (bay seagrasses) situated 9 km away from coral reefs were compared with those of seagrass beds situated on the continental shelf adjacent to coral reefs (reef seagrasses). No differences in total fish density, total species richness or total juvenile fish density and species richness were observed between the two seagrass habitat types. However, at species level, nine species showed significantly higher densities in bay seagrasses, while eight other species showed significantly higher densities in reef seagrasses. Another four species were exclusively observed in bay seagrasses. Since seagrass complexity could not be related to these differences, it is suggested that the arrangement of seagrass beds in the surrounding landscape (i.e. the arrangement on the continental shelf adjacent to the coral reef, or the arrangement in an embayment with mangroves situated away from reefs) has a possible effect on the occurrence of various reef-associated fish species on seagrass beds. Fish migration from or to the seagrass beds and recruitment and settlement patterns of larvae possibly explain these observations. Juvenile fish densities were similar in the two types of seagrass habitats indicating that seagrass beds adjacent to coral reefs also function as important juvenile habitats, even though they may be subject to higher levels of predation. On the contrary, the density and species richness of adult fish was significantly higher on reef seagrasses than on bay seagrasses, indicating that proximity to the coral reef increases density of adult fish on reef seagrasses, and/or that ontogenetic shifts to the reef may reduce adult density on bay seagrasses.     

Impact of cyclones on hard coral and metapopulation structure,connectivity and genetic diversity of coral reef fish

Cyclones have one of the greatest effects on the biodiversity of coral reefs and the associated species. But it is unknown how stochastic alterations in habitat structure influence metapopulation structure, connectivity and genetic diversity. From 1993 to 2018, the reefs of the Capricorn Bunker Reef group in the southern part of the Great Barrier Reef were impacted by three tropical cyclones including cyclone Hamish (2009, category 5). This resulted in substantial loss of live habitat-forming coral and coral reef fish communities. Within 6–8 years after cyclones had devastated, live hard corals recovered by 50–60%. We show the relationship between hard coral cover and the abundance of the neon damselfish (Pomacentrus coelestis), the first fish colonizing destroyed reefs. We present the first long-term (2008–2015 years corresponding to 16–24 generations of P. coelestis) population genetic study to understand the impact of cyclones on the meta-population structure, connectivity and genetic diversity of the neon damselfish. After the cyclone, we observed the largest change in the genetic structure at reef populations compared to other years. Simultaneously, allelic richness of genetic microsatellite markers dropped indicating a great loss of genetic diversity, which increased again in subsequent years. Over years, metapopulation dynamics were characterized by high connectivity among fish populations associated with the Capricorn Bunker reefs (2200 km²); however, despite high exchange, genetic patchiness was observed with annual strong genetic divergence between populations among reefs. Some broad similarities in the genetic structure in 2015 could be explained by dispersal from a source reef and the related expansion of local populations. This study has shown that alternating cyclone-driven changes and subsequent recovery phases of coral habitat can greatly influence patterns of reef fish connectivity. The frequency of disturbances determines abundance of fish and genetic diversity within species.

     

Fish assemblages on artificial and natural reefs in the Flower Garden Banks National Marine Sanctuary, USA

 Visual censusing was used to characterize fish assemblages on artificial and natural reefs located within the boundaries of the Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico. Emphasis was placed on determining spatial and temporal patterns in habitat utilization by fishes on an offshore artificial reef (Mobil Platform HI-A389A). Overall, 43 species were observed during diurnal surveys in the upper 24 m of the artificial reef. Midwater pelagic fishes (i.e., carangids and scombrids) accounted for over 50% of all taxa enumerated on the artificial reef; however, these taxa were transient members of the assemblage and were observed infrequently. Labrids, pomacentrids, and serranids were the dominant reef-dependent taxa. Distinct trends in vertical, diel, and seasonal abundances were observed for juvenile and adult fishes. Of the three designated depth zones (upper 1.5–9.0, middle 9.0–16.5; lower 16.5–24.0 m), abundance and species diversity were lowest in the upper zone. Nocturnal counts were characterized by a marked reduction or complete absence of most species, due in part to twilight cover-seeking and movement activities. Seasonal variation in community composition and species abundance (May versus September) was primarily due to recruitment of juveniles (0-age fishes) to the artificial reef in late summer. Increases in total fish abundance (all taxa combined) coincided with both increasing habitat rugosity and degree of fouling. Species richness on natural coral reefs in the FGBNMS was higher than on the artificial reef. Unlike the artificial reef, fish assemblages on the natural reefs were dominated by a single family (Pomacentridae) which accounted for over 50% of all individuals observed. Accepted: 1 August 1996