Composition and structure of fish assemblage from Passa Cinco stream, Corumbataí river sub-basin, SP, Brazil

Al Carmassi,G Rondineli,Fc Ferreira,Fms Braga

doi:10.1590/s1519-69842012000100011

Abstract

The aim of this work was to determine the composition of the fish assemblage of Passa Cinco stream and verify changes in their structure on the altitudinal gradient. Six samples were performed at five different sites in Passa Cinco stream (from the headwater, at order two, to its mouth, at order six), using an electric fishery equipment and gill nets in May, July, September and November of 2005 and January and March of 2006. The indices of Shannon's diversity, Pielou's evenness and Margalef's richness were quantified separately considering the different fishery equipment (nets versus electric fishery equipment). An ANOVA was used to compare samples collected in relation to values of abundance, diversity, evenness and richness. The representativeness of the species was summarised by their average values of abundance and weight. We captured 5082 individuals distributed into 61 species. We observed a trend of increasing diversity, richness and evenness of species from site 1 to 3, with further decrease in sites 4 and 5. The values found for habitat diversity also followed this pattern. Significant differences were found for all three indices considering the electric fishery samples. For individuals caught with nets, only the richness index showed a significant difference. Characidium aff. zebra was an important species in the headwater and transition sites and Hypostomus strigaticeps in middle-lower course sites. Despite the small extension of the Passa Cinco stream, environments structurally well defined were evidenced by the species distribution and assemblage composition along the gradient.

Highlights

Fish distribution in an environment is rarely caused by a single factor
Geomorphology is an important factor affecting the structure of fish communities in lotic environments (Allan, 1997), because from the headwaters to the mouth, the river goes through different terrain features, leading to changes in limnological characteristics and structural environment
According to the river continuum concept (Vannote et al, 1980), we expect a gradual increase in species richness along the gradient, and the area of the middle section as the most diverse

Summary

Introduction

Changes in the fish species composition from the headwaters to the lower parts is a common phenomenon and conceptual models based on temperate rivers seek to explain the mechanisms responsible for these processes (Matthews, 1998). According to the river continuum concept (Vannote et al, 1980), we expect a gradual increase in species richness along the gradient, and the area of the middle section as the most diverse. These changes usually are associated with habitat changes along the gradient (Gorman and Karr, 1978). These changes usually are associated with habitat changes along the gradient (Gorman and Karr, 1978). Matthews and Styron (1981) suggested that the physical and chemical conditions in the headwaters are more stressful than in the lower portions, so that few fish species can colonize these areas

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