Rockpool ichthyofauna of Amazon coastal zone: spatial and environmental effects on species distribution

The present study analysed the effects of environmental and spatial variables on the structure of fish communities inhabiting rockpools in the Amazon coastal zone to test the hypothesis that environmental characteristics and spatial distribution are the principal factors responsible for community structure. In all, 80 pools were sampled, 40 in the rainy season and 40 in the dry season. The pools were located on five sandy beaches of the Amazon coast. In all, 1303 fish were collected, representing 20 taxa distributed in nine orders and 14 families. The abundance and occurrence of different taxa varied considerably, as did beta diversity, ranging from identical to completely different communities. Differences were found in taxa abundance between seasons (rainy and dry) and beach locality. However, for species richness, only differences between seasons were found, showing the effects of spatial and environmental variation in the structure of fish assemblages. This corroborates both spatial and environmental hypotheses of community structure, and reinforces the role of the extreme dynamic conditions, such as tidal range and influence of the rivers that flow into this estuary, in the intertidal zone fish on the Amazon coast.