Effects of cattle intrusion on environmental conditions and fish assemblages of temperate neotropical prairie streams

Livestock grazing is a major economic activity worldwide. Cattle frequently graze and congregate in watercourses and riparian areas because of the availability of water, shade and the quality and variety of forage, thereby altering the ecological condition of stream ecosystems. We have explored the effects of cattle intrusion on the environmental conditions and fish assemblages of four neotropical prairie streams from Argentina’s Pampas region. At each stream, both ungrazed and grazed conditions were surveyed. Water quality, habitat structure, riparian vegetation and fish assemblages were sampled. Significant detrimental changes were observed in environmental conditions of grazed sites in contrast to ungrazed sites. Fish assemblage structure and function were also significantly influenced by the environmental conditions imposed by cattle intrusion. Our results reveal the magnitude and direction of environmental changes imposed by cattle intrusion in prairie streams and highlight several key aspects of fish assemblages and populations that change accordingly. Relevant aspects for conservation and management purposes of these fragile ecosystems, such as protection of riparian vegetation condition and the control of cattle access and social engagement, are discussed.