One for all and all for one: two mixed-species shoaling of stream fish

Abstract

Abstract Shoaling can provide a number of advantages for individual fish, enhancing foraging efficiency and reducing predation risk. We investigated the role of multiple characid species shoaling (Compsura heterura and Serrapinnus piaba) in order to recognize social behavior, foraging strategy, and diet composition in one semiarid stream from northeast Brazil. The study was done by field observations (ad libitum). The most frequent social behavioral (Arranged Mixed-species school - 38.46%) was represented by mixed-species schools structured with large-sized individuals of C. heterura using the school periphery and small individuals of both species using the center of the school. Shoals with lower individuals inhabiting shallow locals and pools presented higher frequency of this behavior. Although foraging behavior did not vary significantly between the two species, each characin species explored distinct food resources, indicating that diet segregation can act as a strategy to both species foraging in the same shoal. These results suggest that C. heterura and S. piaba have mechanisms to facilitate their coexistence in structured mixed-species schools, minimizing the costs of living in groups.