Fig 1.
Map of the study area showing the sampling sites.
The arrow indicates the studied gradient, with sites allocated less than 5 km (circles), from 8 to 10 km (triangles) and more than 11 km (squares) of distance from the river confluence area. Wave exposure (sheltered, empty symbols; exposed, dark symbols).
Table 1.
Results of PERMANOVA testing for differences in fish assemblage structure, in response to distance from the river confluence area, boulder size, number of refuges, benthic cover (covariates), exposure (fixed factor) and year (random factor) and interaction effects.
Fig 2.
Distance-based redundancy analysis (dbRDA) demonstrating the relationships between fish assemblage structure and the covariates.
DI, distance from the river confluence area; BS, boulder size; BC, benthic cover (PCO1 axis); RE, number of refuges. Highest BC values represent reefs dominated by EAM, while lower values represent soft coral dominated-reefs. Sampling sites were indicated according to the proximity of the river confluence area (circle, close; triangle, intermediate; square, far) and degree of wave exposure (sheltered, empty symbols; exposed, dark symbols).
Fig 3.
Relationships between EAM, fleshy algae and soft coral cover with the first PCO axis.
Squares–EAM, circles–fleshy algae, triangles–soft coral. Colors represent the three groups based on the distribution of the sites along the first 2 axes of the dbRDA: Blue, Close reefs, located from 1.4 to 4.5 km; green–Intermediate reefs, located from 8 to 9 km and white–Far reefs, located from 11.2 to 13.1 km.
Fig 4.
Mean abundance (individuals per 40 m2±SE) of selected species.
Three site-groups were defined according to the distribution of the sites along the dbRDA axis. Black and white columns represent sheltered and exposed areas to wave exposure, respectively. Capital letters show pairwise results from PERMANOVA for the three groups. Significant results of pairwise comparisons for wave exposure (p < 0.001): Abudefduf saxatilis = sheltered > exposed; Holocentrus adscensionis = exposed > sheltered; Malacoctenus delalandii = exposed > sheltered; Sparisoma frondosum = exposed > sheltered; Chromis multilineata = exposed > sheltered; Stegastes fuscus = sheltered > exposed.
Table 2.
Key environmental predictors (mean ± SE) by site-groups.
Fig 5.
Relationships between physical, topographic and benthic predictors and fish assemblage parameters.
Scatter plots of the covariates that had a significant effect on fish richness, abundance, biomass and fish trophic group diversity according to PERMANOVA.
Table 3.
PERMANOVA results based on Euclidian distance measures for a. fish richness, b. abundance, c. Biomass and d. Fish trophic group diversity.