Reef fish community structure on coastal islands of the southeastern Brazil: the influence of exposure and benthic cover

Abstract

Patterns of community structure in the marine environment are strongly influenced by population relationships to biotic and physical gradients. The aim of this work is to explore the relationships of tropical rocky reef fish assemblages to wave exposure and benthic coverage in a gradient of distance from the coast. The study was conducted on the Guarapari Islands, southeastern Brazilian coast. Fish were sampled by underwater visual census (166 transects) and benthic cover was estimated with quadrats (223 replicates). Two main kinds of habitats were found to be derived from the close interrelation between exposure and benthic coverage: (1) exposed areas subjected to major hydrodynamic forcing, and (2) sheltered or moderately exposed areas. The first group is associated with mid-water schooling species like planktivorous labrids and Chromis, piscivorous Caranx, as well as gregarious omnivores like Abudefduf and Diplodus. In terms of benthic composition, macroalgae and encrusting calcareous algae prevail in this highenergy habitat. The second group is characterized by site-attached and reef associated species like territorial pomacentrids, invertebrate feeders such as Halichoeres poeyi and Chaetodon striatus, and small cryptobenthic fishes (e.g. blenniids and labrisomids). Turf algae, zoanthids and massive corals dominate this environment. Environmental plasticity is also common with some genera showing high abundances in all habitats (e.g. Holocentrus, Haemulon, Acanthurus). Examples of the coupling of food availability and fish abundance were found. Planktivores, territorial herbivores, macroalgae browsers and spongivores were positively related with the abundance of their preferred food items along the exposure gradient. Within-family analyses of Pomacentridae and Labridae showed that niche partitioning is likely occurring and seems to be mediated by swimming 'ability' and associated feeding performance.

Reef fish community in presence of the lionfish (Pterois volitans) in Santa Marta, Colombian Caribbean

“…La estructura de la comunidad de peces responde a variables bióticas, tales como la abundancia de competidores potenciales (22) y de presas (15). Para el caso actual con la presencia del invasor, luego que Maljkovic et al (23) encontraran en las Bahamas a especies como M. tigris y E. striatus conteniendo como presa al pez león, Mumby et al (24), en la misma región, estudiaron un grupo de meros y chernas tales como E. striatus, M. tigris, M. bonaci, M. venenosa y M. interstitialis, encontrando una reducción lineal de siete veces en la biomasa del pez león en relación con los meros y chernas; por consiguiente, la evidencia sugiere que la depredación por estas especies sí puede cumplir la función de control natural.…”

“…The structure of the fish community is due to biotic variables such as the abundance of potential competitors (22) and prey (15). In this case, with the presence of the invader, Maljkovic et al (23) found that in the Bahamas M. tigris and E. striatus preyed on the lionfish.…”

“…For example, strong correlations have been found between substrate composition and reef fish with specialized diets densities (e.g. butterflyfish and angelfish) and with habitat requirements (gobies and some cardinalfish) (15). When analyzing density of fish biomass, Krajewski and Floeter (17) found a positive correlation with coral coverage, depth and areas protected from waves, where mobile carnivores and invertivores were more influenced by unconsolidated bottoms and substrates, planktivores and omnivores by wave exposure, and herbivores by algae coverage, with the existence of general habits that suggest that the community is dominated by versatile species.…”

“…Relative quantity analysis was considered as the relationship between the number of individuals of a species and the total of all species; in the same way, the relative number of families was determined by comparing its dominance in each locality. For each species, a trophic group was established through bibliographic revisions (carnivore, invertivore, planktivore, and herbivore), (15)(16)(17).…”

“…Para el análisis de la abundancia relativa se consideró la relación entre el número de individuos de una especie y el total de todas las especies; igualmente se determinó la abundancia relativa de las familias para comparar la dominancia en cada una de las localidades. Para cada especie se estableció su grupo trófico a través de revisiones bibliográficas (carnívoro, invertívoro, planctívoro y herbívoro), (15)(16)(17).…”