A ictiofauna do estuário do rio Itanhaém, SP, Brasil: dinâmica espaço-temporal e aspectos biológicos das espécies principais / Itanhaém River Estuary, SP, Brazil: Spatial and seasonal changes in fish assemblages and biological aspects of the principal species

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The changes of the composition and the distribution of the fishes along the Itanhaém River Estuary were investigated, between May 2002 and April 2003. Biologic aspects of principal species were also included. The month sampling of the fishes was performed using otter trawls in three different areas in the estuary (A1, A2 and A3). Samples were also collected from another location in adjacent marine area (EXT area). The duration of the fishing trawls was of 10 minutes. Temperature data, salinity, pH, water transparency, dissolved oxygen were obtained. Simultaneously, surface sediment sample was taken for evaluation of organic matter, and the grain size. All fish collected were identified to species, counted and measured for total length and wet mass (g). The analyses of the structure of the fauna involved the occurrence of species, the abundance in number and capture weight. The following indexes of community structure were also obtained: the species richness, the species richness of Margalef, diversity of Shannon-Wiener, and the evenness of Pielou. The TWINSPAN analysis (Two Way Indicator Species Analysis) and nonmetric multidimensional scaling (MDS) were used to identify species groups and/or sampling groups. The BIO-ENV routine was used to relate the biological patterns to the environmental pattern. Values of salinity were higher in winter and spring, and were lower in summer and autumn, because the estuary receives relatively high inputs of freshwater of the rain. A total of 13802 specimens of teleostean fishes were collected, weighing 210.662,2g, belonging to 53 species. The ichthyofauna was composed of marine and estuarine-related species. Eight species constituted 86% of the capture in number and 87,4% in weight. The results showed that only the species richness and species richness of margalef differed significantly among seasonal samples. The TWINSPAN analysis separated two samples groups and two species groups those were formed because the distinct pattern of EXT area. The MDS ordination plot three spatial groups of samples: G1- was formed by samples from the internal area (A3) with the summer/autumn samples from A2 area; G2 ? was formed by the samples from A1 area with the winter/spring samples from A2 area. The third group (G3) was formed by samples with the dominance of Achirus lineatus. The factors, environmental pH, temperature and sand, seem to have an influence in the structure of the fauna patterns. The most important species were Genidens genidens, G. barbus, Bairdiella ronchus, Achirus lineatus e Trinectes paulistanus. Among them, only Bairdiella ronchus and Achirus lineatus were represented by adult specimens. Genidens Genidens, G. barbus and Trinectes paulistanus were represented by high proportions of juvenile individuals in the estuary. Diets of those five species were investigated based on the stomach contents. Achirus lineatus and Trinectes paulistanus fed mainly on Polychaeta; Genidens barbus and Bairdiella ronchus ingested Dendrobranchiata and Teleostei, and a great number of benthic invertebrates composed the diet of Genidens genidens. They presented partial diet overlap, and to avoid this, they occupied different areas.

ASSUNTO(S)

ictiofauna estuário fish assemblages rio itanhaém itanhaé river estuary genidens genidens

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