Moon and tide effects on fish capture in a tropical tidal flat

The influence of the lunar phases and tidal range on the fish capture was analysed in a tidal flat in Barra do Paraguaçu (Baía de Todos os Santos). The sampling was realized in the flood tide and ebb tide of the spring (full moon) and neap (waning moon) tides, between June 2007 and May 2008. At all sampling occasions, two parallel drags were accomplished to the tidal flat, in the same direction of the current, in a 100 m long area marked on the beach beforehand, using a seine net of 15 m × 2.0 m with a mesh of 12 mm between adjacent knots. A total of 2312 fish specimens were captured (26.5 kg), belonging to 75 species from 45 families. The mean number of captured fish was significantly larger in full moon at ebb tides, while the mean weight in the captures was larger in ebb tides. There was significant difference in number of species, number of fish, richness and diversity between full and waning moons. The number of fish and biomass were significantly different between tides. Significant differences were found in community structure regarding trophic groups in relation to tide and moon, although the classic diversity indices did not capture this effect between tides. Furthermore, it was possible to identify preferences of occurrence related to the change of tide in dominant species.

Population structure of Oncholaimus cobbi (Nematoda: Oncholaimidae) in a tropical tidal flat

Oncholaimus cobbi was described from the Brazilian coast. The area studied, Coroa Grande, is located in Sepetiba Bay, State of Rio de Janeiro, Brazil. Sampling was carried out monthly, from May 1998 through April 1999. Most of the population was represented by adults, of which non-ovigerous females were the most abundant category. The species reached its highest population density during the warmest months, and the highest densities of males and ovigerous females were seen in February 1999.