Movement and activity patterns of the black piranha

Adult black piranhas, Serrasalmus rhombeus, were radio-tracked using purpos e built equipment in the 2.6 km long oxbow lake Coco Cocha, south east Peru during a five month period in the dry season of 1995. Fish were tagged ext ernally in front of the dorsal fin. S. rhombeus showed generally localised movements in different sections of the lake with only one making use of its whole length during the tracking period. S. rhombeus in the shallower extr eme sections of the lake were seen to make frequent trips into flooded fore st. Speed plots and perceived activity plots revealed cyclic patterns of mo vement and activity synchronised with dawn. Those fish tracked at night wer e active until after dark and sometimes throughout the night into the early hours of the morning.