Community structure and temporal variability of ichthyoplankton in North Brazilian mangrove creeks

The species composition and dynamics of fish larvae in three mangrove creeks located in the Caeté Estuary (north Brazil) were studied monthly using a trap net during diurnal ebb tides. A total of 109 954 larvae, representing 25 families and 54 species, were collected from October 1996 to October 1997. The community was dominated numerically by a few species, a feature common for other estuarine fish populations. The most abundant taxa were estuarine species, namely the eleotrid Guavina guavina (46·7%) and the engraulid Anchovia clupeoides (14·9%). The sciaenid Cynoscion acoupa was the only marine species that used the mangroves extensively as a nursery site, occurring mainly at the postflexion stage. The size distribution of G. guavina did not produce shifting modes, indicating continuous transport out of the mangroves by tidal currents. Significantly lower species richness was observed in the late rainy season, primarily due to the emigration of marine species. Intermediate seasons were characterized by more complex larval fish assemblages. The temporal trends of the dominant species was influenced to a great degree by their life history strategy.     

Spatial and temporal distribution of Myrophis punctatus (Ophichthidae) and associated fish fauna in a northern Brazilian intertidal mangrove forest

The mangrove forest along the northern Brazilian coast is not inundated during low tide. However, many fish species stay in the mangrove forest during this time. Tidal behaviour strategies are described for fish species that linger in the mangrove forest during low tide. The samples were taken at the end of the dry season (December 1996) and at the end of the rainy season (July 1997). Fish were captured using an ichthyotoxic plant extract (Ichthyotere cunabi). Spatial and temporal fish density and biomass were analyzed statistically. Thirty-six samples were taken with a total density of 2.8 ind m^-2 and a total biomass of 17.4 g m^-2 distributed among seven families and 14 species. Myrophis punctatus was the most important species in number (1.66 ind m^-2) and weight (12.68 g m^-2) of all catches. The total fish densities were not significantly different among areas and between months, although, total biomass differed significantly in time and space. The densities and biomass for the three most dominant species (M. punctatus, Poecilia spp. and Gobionellus smaragdus) differed significantly among species. Only the biomass of these species showed significant monthly differences. The only significant main effect on variance in the densities and biomass of M. punctatus were encountered between months. In addition, the factor area was significantly different for the variable number of species.