Tides, Salinity, and Biogeography Affect Fish Assemblage Structure and Function in Macrotidal Mangroves of the Neotropics

Identifying the drivers that explain the distribution of tropical coastal fishes remains a central goal in biogeography. However, a lack of comparisons with standardized data still prevents more robust generalizations. Here, we assess if general assembly rules apply in two intertidal mangrove fish assemblages from different biogeographical regions (Tropical Eastern Pacific and Western Atlantic). Using multivariate analyses on field data collected for about 1 year at each location, we examined if different community attributes (species richness, taxonomic, and trophic composition, density, and catch mass) varied temporally (according to tidal-diel rhythms) and spatially (salinity gradients and between biogeographical regions). Similar total fish species richness (ca. 50 species) mirrored the regional species richness of coastal fishes in these regions. Pufferfishes (Tetraodontidae) and catfishes (Ariidae) dominated (in catch mass) fish assemblages in both regions. Closely related species within these families responded in similar ways to tidal-diel changes suggesting the existence of a phylogenetic signal in temporal niche use. The strength of the influence of tidal-diel forces determining fish habitat use were likely related to differences in mangrove topography. The biogeography of the adjacent freshwater fish fauna could explain differences in taxonomic and trophic composition between regions. Our results highlight the role that tidal-diel dynamics play in influencing the structure of fish assemblages in macrotidal areas, and suggest that considering the regional biogeographical history and the local seascape configurations could help to explain differences in mangrove fish assemblage structure across regions.