ENVIRONMENTAL DRIVERS OF FISH ASSEMBLAGES FROM THE SHALLOW INFRALITTORAL AREAS OF THE PARANAGUÁ BAY, SOUTHERN BRAZIL

Estuaries are environments with exceptional productivity, characterized by large fluctuations of abiotic factors. In these environments, the composition of the fish fauna is dynamic and complex. Despite the variation in the fish fauna in the estuaries, it is possible to observe some populations associated with microhabitats. The individuality of these communities is apparently derived from habitat selection. Aiming to examine the composition of the demersal fish fauna of the Paranagua Bay, monthly collections were conducted using an otter trawl, from October 1999 to September 2000, at five sites in the shallow infralittoral. In each collection, water samples were also taken for determination of pH, dissolved oxygen, seston, nutrients. Temperature and salinity were also measured. The discriminant analysis showed a gradient in the phosphate concentration, with higher values in the innermost areas of the bay in relation to the external areas. The phosphate found in the region may be of allochthonous (pollution and leaching) and autochthonous (decomposition) origin. The salinity and the dissolved oxygen showed higher values in the outermost areas under the stronger marine influence. A total of 6,633 fish specimens belonging to 55 species and 27 families were collected. Cathorops spixii catfish foi a especie mais abundante com 21% do total capturado em numero. A diversidade foi significativamente diferente apenas em Pontal do Sul, mas houve diferencas evidentes na composicao e abundância da ictiofauna entre as areas de estudo. Tais diferencas parecem estar relacionadas com a complexidade dos habitats, o que ocorre devido ao diferente fundo encontrado em cada local de amostragem.