Vertical segregation of serrapinnus piaba and serrapinnus heterodon (characiformes: characidae) in a river stretch in northeastern Brazil

Abstract

The objective of this study was to evaluate the occupation in the water column by the fish species Serrapinnus piaba and S. heterodon and test for correlations between abundance and environmental characteristics. The study was conducted in a tributary of the Curu river, in semi-arid Northeastern Brazil. Snorkelers made day-time observations of behaviors: water column occupation, foraging, social organization, syntopy and agonism. The environmental characteristics included river depth, width and current speed in sampling areas dominated by Ceratophyllum demersum beds. The two species differed significantly with regard to the frequency of all behaviors, and presented inverse, though not statistically significant, correlations with environmental characteristics. The absence of statistical significance may be explained by the presence of abundant C. demersum beds favoring the heterogeneity of current speed and microhabitats. In conclusion, vertical segregation was observed between S. piaba (n=45) and S. heterodon (n=93) in an environment attenuated by the presence of macrophytes; however, further studies are required to determine the original cause of this segregation.