Selection of netted prey by piranhas, <em>Serrasalmus spilopleura</em> and <em>S. marginatus</em> (Pisces, Serrasalmidae)

Abstract

The frequency of attacks by piranhas on specimens of netted fish was analyzed from monthly catches in gill nets set out for 24 hours and checked every 8 hours, from June 1987 through May 1988, in lakes, channels, and rivers of the upper Paraná river floodplain, Brazil. Captured fish were identified and marks of attack by piranhas on their fins and flesh were recorded. The probability of detection of netted fishes, their body structure, and behavioral aspects were the factors determining the selective piranhas attacks. There was no significant relationship between the frequency of predator attacks and the relative abundance of the prey. Community composition was the main factor determining the attack frequency, which differed according to environment