Non-native white piranhas graze preferentially on caudal fins from large netted fishes.

In this study we assessed, for the first time, grazing by Serrasalmus brandtii outside its natural range. We observed higher grazing proportions in samples from sites where S. brandtii is the dominant species in relation to sites where it is recorded as present and sites where it is absent. S. brandtii grazed preferentially on caudal fins in relation to all other fins alone or combined. It also preferred to mutilate fins instead of flesh. Larger fish had a higher probability of being mutilated and had a higher number of mutilated fins than smaller fish, which is expected as large fish represent a larger resource to their consumers. S. brandtii avoided mutilating conspecifics and, as its abundance increased, so did the number of species being preferentially grazed. White piranhas were introduced in the Jequitinhonha River basin and increased the incidence of mutilation on netted fishes. This species preferentially grazed on caudal fins from large fishes, without, in most cases, killing its prey. Interestingly, white piranhas avoided cannibalism, and, as its abundance increased, so did the number of species being preferentially grazed. [ABSTRACT FROM AUTHOR]