ABSTRACT
The advance of the agricultural frontier is one of the biggest threats to the communities' structure of the fish assemblages in headwaters streams. The influence of land use and occupation on the fish assemblages structure in headwater streams was evaluated in three stream reaches in the Upper Paraguay River Basin, state of Mato Grosso, Brazil. Samples were collected from July to December 2013 using dragging net and sieve in Ararão, Queima Pé e Russo streams, municipality of Tangará da Serra. Totals of 35 species encompassing 4,192 individuals were collected, and the dominant species within were Moenkhausia lopesi (Britski & de Silimon, 2001) e Knodus moenkhausii (Eigenmann & Kennedy, 1903), accounting for 68.5% of the individuals. There were no significant differences in richness or abundance among the three streams, but Shannon diversity index was higher in the Russo stream (H´ = 2,33). The high percentage of native vegetation converted into agriculture crops (49.20%) and cattle raising (30.69%), disclosed a strong negative relationship between agriculture and richness, showing that as the agriculture fields become smaller the species richness becomes larger.
KEYWORDS
Fish; richness; abundance; deforestation
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