Abstract
The aim of this study was to investigate the influence of spatial variation in river channels and habitats on the distribution of fish communities in the headwater streams of the Jaú River System, a blackwater tributary of the Negro River. Collections and measurements were made in 34 headwater streams during the period of November- December, 1998. Fish were captured with fish traps and hand nets along standard reaches of two meanders. Data on benthic habitat structure, stream depth and width were collected along lateral transects in each sample reach. A total of 66 fish species from 24 families were collected and classified into seven trophic guilds: allocthonous insectivore, autochthonous insectivore, general insectivore, piscivore, detritivorous planktivore, detritivorous insectivore and insectivorous piscivore. Variations in the distribution and diversity of bottom substrates were important factors influencing fish community structures in these systems. Also, variation in stream size explained the observed variability in fish communities.
Highlights
The variation in channel width is a key factor that influences the distribution of submerged branches, trunks and fine litter as well as the availability of light and the distribution of aquatic vegetation and fauna along the fluvial system (Cummins, 1974; Conners and Naiman, 1984; Walker, 1987)
Fish were collected in 34 streams and the most numerically abundant family was Characidae with 568 individuals in one stream
The physical characteristics vary systematically along the stream size, and this gradient results in a continuum biotic adjustment which was predicted by the River Continuum Concept (Vannote et al, 1980)
Summary
The variation in channel width is a key factor that influences the distribution of submerged branches, trunks and fine litter as well as the availability of light and the distribution of aquatic vegetation and fauna along the fluvial system (Cummins, 1974; Conners and Naiman, 1984; Walker, 1987). Studies of fish communities in temperate and tropical streams have shown that most species tend to occur in a restricted number of habitats (Zaret and Rand, 1971; Saul, 1975; Soares, 1979; Vianna, 1989; Rinne, 1992; Silva, 1993). Choosing a place to live depends on food availability, tolerance to physical or chemical factors, and predation intensity (Rinne, 1992). Choosing a place to live depends on food availability, tolerance to physical or chemical factors, and predation intensity (Rinne, 1992). Caramaschi (1986) found that fish distribution in the small streams of the
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