Distribuição espaço-temporal das larvas de peixe e sua relação à hidrodinâmica e à qualidade da água no entorno das ilhas do Combu e Murucutu, Belém - PA

Abstract

In order to compensate for the lack of information on fish larvae communities in the Amazonians region, this study aims to investigate the spatial and temporal variation of larval density, diversity in relation to taxa and development stages. Data collected were related to water quality and hydrodynamic features at sample stations. Samples were taken in October/2008, January, April and July/2009 according to the pluviometric index. Samplings occurred in the Guama and Benedito Rivers bordering the Combu and Murucutu Islands as well as in the Paciência Canal which separates the two islands. The larvae were captured towing a conical plankton net with 330 μm mesh size, 0.5 m of diameter and 2.5 m in length. In parallel surface water were taken, for water quality analysis, and data hydrodynamic. Data were registered included univariate (ANOVA) and multivariate (PCA; RDA) approaches. Larval community included 4.983individuals distributed among the Clupeidae, Engraulidae, Sciaenidae, Carangidae, Tetraodontidae and Hemiramphidae families. The families Clupeidae and Engraulidae dominated, followed by the Sciaenidae family. The peak of larvae as well as the highest density of preflexion stage was registered in October/2008, during dry season pointing at a major spawning event. The Paciência Canal presented a higher larval abundance on its northern side, probably in relation to the strong water flow from the Guamá River. Moreover, the Paciência Canal presented differentiated larval densities for presenting more favorable environmental characteristics. In the area east of the Guamá River larvae were also abundant probably represent a less agitated than the area west. In the East side of the Guamá River larvae were also abundant, probably due to its quieter water when compared to the West side that received the ebbing waters of the Paciência Canal. Among all the parameters taken into considerations, the hydrodynamic were the only ones who showed the best associations to the larval communities. Distribution of larvae at different development stages remained constant over time. Taxa distribution only presented different in October/2008. Diversity and larval density was considered low, which may be related to huge input of freshwater. Water quality was not considered as a limiting factor for fish larvae growth and survival. Water dynamic in the Paciência Canal indicated that there is a restriction in the transport of fish larvae between Guamá and Benedito Rivers.