Fishes--Tropics

Small clear and blackwater streams of the neotropics are economically important because they may be nursery grounds for important food and aquarium fishes. At present, these ecosystems are being negatively impacted by current logging, and gold and diamond mining practices. Thus, the role of biotic and abiotic factors in fish community structure was examined in three unimpacted streams in Guyana, South America. These streams had relatively low fish species diversity, but complex feeding guild structure. No significant correlations between abiotic factors and fish species diversity and feeding guild diversity were determined due to small sample size. However, principal component analysis suggested an association between pH and species diversity, and conductivity and guild diversity. Biotic factors, such as competition and predation may be the primary determinant of fish community structure and organization in neotropical blackwater streams.