Distribution Of Coral Reef Fishes Research Articles

A study on the occurrence and distribution of coral reef fishes along Cuddalore fish landing center, Tamilnadu, India

A study on the occurrence and distribution of coral reef fishes along Cuddalore fish landing center, Tamilnadu, India

Fishing and habitat condition differentially affect size spectra slopes of coral reef fishes.

Marine food webs are structured through a combination of top-down and bottom-up processes. In coral reef ecosystems, fish size is related to life-history characteristics and size-based indicators can represent the distribution and flow of energy through the food web. Thus, size spectra can be a useful tool for investigating the impacts of both fishing and habitat condition on the health and productivity of coral reef fisheries. In addition, coral reef fisheries are often data-limited and size spectra analysis can be a relatively cost-effective and simple method for assessing fish populations. Abundance size spectra are widely used and quantify the relationship between organism size and relative abundance. Previous studies that have investigated the impacts of fishing and habitat condition together on the size distribution of coral reef fishes, however, have aggregated all fishes regardless of taxonomic identity. This leads to a poor understanding of how fishes with different feeding strategies, body size-abundance relationships, or catchability might be influenced by top-down and bottom-up drivers. To address this gap, we quantified size spectra slopes of carnivorous and herbivorous coral reef fishes across three regions of Indonesia representing a gradient in fishing pressure and habitat conditions. We show that fishing pressure was the dominant driver of size spectra slopes such that they became steeper as fishing pressure increased, which was due to the removal of large-bodied fishes. When considering fish functional groups separately, however, carnivore size spectra slopes were more heavily impacted by fishing than herbivores. Also, structural complexity, which can mediate predator-prey interactions and provisioning of resources, was a relatively important driver of herbivore size spectra slopes such that slopes were shallower in more complex habitats. Our results show that size spectra slopes can be used as indicators of fishing pressure on coral reef fishes, but aggregating fish regardless of trophic identity or functional role overlooks differential impacts of fishing pressure and habitat condition on carnivore and herbivore size distributions.

Habitat morphology constrains the depth distribution and growth rate of a coral-associated reef fish

The distribution of coral reef fishes is often closely linked to the availability of preferred habitats. However, even in specialized gobies associated with a single coral species, their distribution does not always match that of the coral host. The coral goby Paragobiodon xanthosoma is primarily restricted to shallow water ( 30 m. Here, we use observational and experimental approaches to test whether depth-associated changes in morphology and partial mortality of the coral decrease habitat quality. Quantitative surveys from the surface to 30 m found pronounced changes in colony morphology over depth. S. hystrix colonies most likely to be occupied by P. xanthosoma were those with shallow-water characteristics, especially lower partial mortality and a more complex branching structure. In a binary choice experiment, P. xanthosoma individuals preferentially selected colonies from shallow water (5 m) over deep water (30 m) and with high complexity over low complexity when colonies were collected from a standardized depth (15 m). Finally, a transplant experiment examined the effect of depth-associated changes in the coral habitat on patterns of growth of P. xanthosoma. When the depth of placement was standardized, the growth of P. xantho soma was 8-fold lower on colonies collected from deep water (30 m) compared to colonies from shallower water (5 and 15 m). Together, these patterns suggest that depth-related changes in the morphology of the coral host are responsible for driving patterns of distribution over depth in their associated reef fish.

Environmental factors that influence the distribution of coral reef fishes: modeling occurrence data for broad-scale conservation and management

To manage coral reef species, it is important to identify the factors that determine their distribution inexpensively. We identified the remotely measured environmental factors that are most influential in determining the distributions of coral reef fish species on a regional scale. Logistic regression models for 227 fish species related presence/absence data to 4 remotely determined environmental predictor variables: depth, presence of a land–sea interface, exposure, and the distance to the nearest estuary. We compared modeled Akaike information criterion (AIC) values with AIC values of randomly distributed species with different numbers of occurrences and levels of habitat specificity to evaluate model significance. Efficient species distribution models were identified for 118 predominantly habitat-specific fishes of the 227 species for which we had data. All 4 predictor variables significantly influenced the distributions of at least some fish species. Depth was the most frequently efficient variable for single variable models. For combinations of 2 predictor variables, depth and exposure, as well as depth and distance from the nearest estuary, were the prevalent predictors of fish distributions. Several fish species responded to the combination of variables distance from an estuary and presence of the terrestrial–marine interface, indicating that these species depend on intact coastal reef habitat, which is in decline near the main sediment-laden rivers. Statistically significant models were predominantly developed for habitat-specific species. These habitat-specific species are of greater conservation concern than widespread species because threats affect them more severely if the threats are selectively affecting their habitat. For this reason, species distribution modeling using remotely determined environmental data may be an efficient method to build models for habitat-specific species and inform marine reserve design.

Distribution of coral reef fishes along a coral reef-seagrass gradient: edge effects and habitat segregation

Coral reefs and seagrass beds are often located adjacent to one another, but little is known about the degree to which their fish communities are interlinked. To determine whether coral reef fishes on the coral reef are interlinked with or segregated from fishes on adjacent seagrass beds, a 60 m coral reef-seagrass gradient was studied on the island of Zanzibar in the western Indian Ocean. Using underwater visual census, coral reef fishes were surveyed in 4 habitat zones: (1) a coral patch reef, (2) seagrass beds bordering the coral reef, (3) seagrass beds at a 30 m distance from the coral reef edge and (4) seagrass beds at a 60 m distance from the coral reef edge. Based on the den- sities of juveniles and adults in the 4 zones, the 48 species that were observed were classified into reef-associated species, seagrass-associated species, nursery species, generalists and rare species. Reef-associated species occurred almost exclusively on the coral reef and at the reef-seagrass edge, while seagrass-associated species occurred almost exclusively on the seagrass beds. Generalists and seagrass-associated species occurred in all 3 seagrass zones, but densities of generalists on seagrass beds decreased with increasing distance from the reef, whereas that of seagrass-associated species increased. Reef-associated and generalist species showed an edge effect, where densities on the sea- grass beds near the reef edge were higher than on the seagrass beds further away. Juvenile densities of nursery species on seagrass beds also increased with the distance from the reef, whereas their adults showed the highest densities on the coral reef, suggesting a possible ontogenetic shift from the seagrass beds to the reef. The results of the present study show that this seagrass-coral reef land- scape features habitat segregation between species and life stages and shows an edge effect, possibly driven by competition mechanisms between species or life stages.

The relationship of reef fish densities to the proximity of mangrove and seagrass nurseries

Visual census surveys were used to study the distribution of coral reef fishes that are associated with seagrass beds and mangroves in their juvenile phase, on various coral reef sites along the coast of the Caribbean island of Curaçao (Netherlands Antilles). The hypothesis tested was that various reef fish species occur in higher densities on coral reefs adjacent to nursery habitats than on reefs located at some distance to these habitats. Of 17 coral reef fish species that are known to use bays with seagrass beds and mangroves as nurseries (nursery species), 15 were observed in quadrats on the reef. Four nursery species, Haemulon sciurus, Lutjanus apodus, Ocyurus chrysurus and Scarus coeruleus occurred in significantly higher densities on coral reefs adjacent to bays with seagrass beds and mangroves. Lutjanus analis, Lutjanus mahogoni and Sphyraena barracuda also had their highest densities on reefs adjacent to these bays, although differences between the distinguished reef categories were not always significant. It is suggested that these seven species are highly dependent on the presence of bays with seagrass beds and mangroves as nurseries on an island scale. Eight other species that are known to use seagrass beds and mangroves as nurseries did not have their highest densities on reefs adjacent to bays with seagrass beds and mangroves. For six of these species, juveniles were also observed on the reef. It is suggested that these species are able to use the reef as an alternative nursery and do not depend strictly on the presence of bays with seagrass beds and mangroves as nurseries.

Population Dynamics and Spatial Distribution of Coral Reef Fishes: Comparison Between Continuous and Isolated Habitats

Recent studies have shown that there are high degrees of spatial and temporal stability in coral reef fish assemblage structures in a continuous habitat, in contrast to results of observations in isolated habitats. In order to determine the reason for the difference in temporal stability of fish assemblage structures in a continuous habitat site and an isolated habitat site, population dynamics and spatial distributions of coral reef fishes (six species of pomacentrids and two species of apogonids) in the two habitat site were investigated over a 2-year period in an Okinawan coral reef. The population densities of pomacentrid and apogonid species increased in juvenile settlement periods at both sites, but the magnitude of seasonal fluctuation in population density was significantly greater at the isolated habitat site, indicating that the rate of juvenile settlement and mortality rate in the isolated habitat were greater than those in the continuous habitat. The magnitude of aggregation of fishes, which affects density-dependent biological interactions that modify population density such as competition and predation, was also significantly greater at the isolated habitat site, especially in the juvenile settlement season. Most of the fishes at the isolated habitat site exhibited more generalized patterns of microhabitat selection because of less coral coverage and diversity. The seasonal stability in the species composition of fishes was greater at the continuous habitat site than that at the isolated habitat. Our findings suggest that the relative importance of various ecological factors responsible for regulation of the population density of coral reef fishes (e.g., competition, predation, microhabitat selection and post-settlement movement) in a continuous habitat site and the isolated habitat site are different.

Effect of a marine reserve on the distribution of coral reef fishes in Barbados

Effect of a marine reserve on the distribution of coral reef fishes in Barbados