Resumo

CHERNOFF, BARRY; WILLINK, PHILIP W  e  MACHADO-ALLISON, ANTONIO. Spatial partitioning of Fishes in the río Paraguay, Paraguay. INCI [online]. 2004, vol.29, n.4, pp.183-192. ISSN 0378-1844.

The 173 species of freshwater fishes collected during the AquaRAP expedition to the Río Paraguay were analyzed to determine if distributional patterns existed within the region. The region was divided into five subregions and into eight macrohabitats. Two null hypotheses were tested and rejected: i) that fishes are randomly distributed with respect to subregion, and ii) that fishes are randomly distributed with respect to macrohabitat. The results show a strong subregional effect, such that two distributional elements were present. One consists of an association between the Río Paraguay and Río Negro subregions. The other consists of Río Apa and Riacho La Paz subregions. The analysis of distributions with respect to macrohabitats also reveals two components. The first relates the beach and main channel faunas to the macrohabitats that are inundated during seasonal flooding, such as flooded forests and lagoons. The assemblage associated with the flooding cycle accounts for more than 75% of the fishes collected. The second component comprises habitats found within Río Apa and Riacho La Paz (e.g. clear water, rapids, etc.). This component has a relatively sharp boundary with respect to Río Paraguay, with more than a 50% turnover in fauna. These results show that core conservation areas must be set up within situations in which the seasonal flooding cycle is unimpeded and the area of inundation is relatively unmodified. Also, Río Apa and Riacho La Paz represent a highly threatened area because of high rates of land conversion, aridity, and the fact that much of the fauna cannot be recolonized from nearby water sources.

Palavras-chave : Conservation; Distribution; Fishes; Freshwater; Paraguay .