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.

A dinâmica populacional e a produção secundária do poliqueta Euzonus furciferus foi estudada em uma praia arenosa exposta do sul do Brasil. O estudo foi realizado na praia de Atami, de fevereiro de 1992 a março de 1993. Euzonus furciferus Ehlers, 1897 é a única espécie comedora de depósito da região superior do intermareal. Os organismos foram encontrados na praia ao longo de todo o ano, concentrados em uma estreita faixa, e alcançando densidades máximas de 3.029 indivíduos.m-2. Picos de abundância ocorreram em setembro de 1992, com uma média de 681,8 indivíduos.m-2. O recrutamento ocorreu no inverno, com um pico em julho. A biomassa média anual foi estimada em 0,218 gPSLC m-2, com uma produção anual total de 0,466 gPSLC m-2ano-1, e com uma razão P/B de 2,13 ano-1. Valores similares foram encontrados para um poliqueta filtrador existentes na mesma praia, sugerindo que a disponibilidade geral de alimento para cada ambiente particular é mais importante para a produção do que a estratégia trófica empregada pelos organismos que exploram este ambiente.

The distribution, population dynamics and secondary production of the polychaete Euzonus furciferus was studied in Atami Beach (Southern Brazil), from February 1992 to March 1993. Euzonus furciferus Ehlers, 1897 is the only deposit feeder species of the upper intertidal region. The organisms were present in the sandy beach all over the year, concentrated in a narrow band, and reaching maximal densities of 3,029 individuals m-2. Peaks of abundance occurred in September 1992, with a mean of 681.8 individuals m-2. Recruitment occurred in winter, with a peak in July. Mean annual biomass was estimated in 0.218 gAFDW m-2, with a total annual production of 0.466 gAFDW m-2 y-1, giving a P/B ratio of 2.13 y-1. Similar values were found for a filter-feeder polychaete inhabiting the same beach, suggesting that general food disposability of each particular environment is more important for production than the trophic strategic employed by those organisms exploring this environment.

O molusco Mytilopsis leucophaeta (Conrad, 1831), natural da América do Norte, foi localizado no litoral de Pernambuco, Brasil, em 2004, trazido provavelmente por água de lastro de navios. Na região, sua distribuição atualmente abrange zonas estuarinas adjacentes ao Porto do Recife. Os organismos foram encontrados restritos à região entre-marés, formando agregados densos com até 176.800 ind./m².

The mussel Mytilopsis leucophaeta (Conrad, 1831) is native to North America. It was found at Pernambuco Coast, northeastern Brazil, in 2004, probably brought by ships' ballast water. The distribution of this species has been now spread to estuarial area near Recife Harbour. They showed a clumped distribution with a maximum of 176,800 ind./m² only in the intertidal zone.