Food Habits of Piranhas in the Low Llanos of Venezuela

Eight piranha species (Characidae: Serrasalminae) coexist in streams and pools of the western Orinoco River Basin Ilanos. The species differ in adult size, body form, and relative abundance. Examination of some 1300 specimens collected over a seven-year period (1979-1985) showed that food habits and diet diversity usually change with age. Small juveniles of the abundant and widespread Pygocentrus notatus eat microcrustaceans and aquatic insects. Above 40 mm standard length (SL), they take small fish and chunks of fish flesh. Small juveniles (20-80 mm SL) of six species (Serrasaimus altuvei, S. irritans, S. cf elongatus, S. rhombeus, S. caribe, and Pristobrycon cf striolatus) specialize in fins of other small fishes, but by 80 mm SL their diets shift to small fish, pieces of fish flesh, and fins. However, all sizes of Catoprion mento eat scales. Considerable diet overlap among different piranha species in the same size dasses suggests that plentiful food resources are not limiting. These savanna piranhas do not depend on fruits and seeds as has been reported for piranhas in flooded tropical rain forests.