Spatial distribution of the estuarine ichthyofauna of the Rio Formoso (Pernambuco, Brazil), with emphasis on reef fish

The objectives of the present study were to identify species of reef fish that use the Rio Formoso estuary (northeastern Brazil) as a refuge and natural nursery and to describe the spatial distribution of the estuary fish fauna in rainy and dry seasons. A total of 5475 specimens, across 78 species and 39 families, were analyzed; 51.3% of the species were of reef origin. Among these, Eucinostomus melanopterus (Bleeker, 1863), E. gula (Cuvier, 1830), and Sphoeroides testudineus (Linnaeus, 1758), in this order, were the most abundant in the upper estuary; S. greeleyi Gilbert, 1900, E. melanopterus, and Lutjanus synagris (Linnaeus, 1758) were the most abundant in the mid estuary; and E. gula and Albula vulpes (Linnaeus, 1758) in the lower estuary. The percentages of reef species were 39.2%, 54.2% and 66.7% for the upper, mid and lower regions, respectively. The greatest diversity was found in the upper estuary and greatest abundance occurred in the mid region. The type of sediment was a strong determinant of the spatial distribution of fish fauna. The most abundant species were found in a mesohaline (5-18) to euhaline (30-40) salinity regimen, suggesting some capacity for osmotic regulation. The fish fauna of the Rio Formoso estuary receives a direct influence from the reefs and coastal region between Sirinhaém and Tamandaré, thereby providing a greater richness of reef fish