Abstract
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.
Highlights
Fish constitute around 99% of the nektonic species in estuarine environments, where they transform the energetic potential of detritus, carrying energy from the lowest to the highest trophic levels, allowing exchanges between neighboring ecosystems and storing energy by entering estuaries, where they remain throughout part of their lives (ARAÚJO et al 2004)
The spatial distribution of fish communities in each estuary can vary according to the characteristics of the sediment and the heterogeneity in the substrate, as well as the presence of vegetation, which affects prey availability (BLABER & BLABER 1980, GARCIA & VIEIRA 1997, MARSHALL & ELLIOTT 1998, VIEIRA et al 1998)
Thirteen species were captured only in the upper estuary region, nine in the mid estuary, and six in the lower estuary; 23 species were found both in the upper and mid regions, 12 in the mid and lower regions, and 15 species occurred in all regions
Summary
Fish constitute around 99% of the nektonic species in estuarine environments, where they transform the energetic potential of detritus, carrying energy from the lowest to the highest trophic levels, allowing exchanges between neighboring ecosystems and storing energy by entering estuaries, where they remain throughout part of their lives (ARAÚJO et al 2004). Estuarine systems present high abundance of young fish of reef origin (MUMBY et al 2004, DORENBOSCH et al 2004, MUMBY 2006), which use shallow habitats in the estuaries, such as marine phanerogam meadows and mangroves, as nurseries (DORENBOSCH et al 2004) and shelter (SHULMAN 1985). In these environments, these fish find a broad variety of feeding resources during their growth (WERNER & GILLIAM 1984), due to the elevated primary production and consequent increased secondary production (ROBERTSON & BLABER 1992). The spatial distribution of fish communities in each estuary can vary according to the characteristics of the sediment and the heterogeneity in the substrate, as well as the presence of vegetation, which affects prey availability (BLABER & BLABER 1980, GARCIA & VIEIRA 1997, MARSHALL & ELLIOTT 1998, VIEIRA et al 1998)
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