I went piranha fishing in the Amazon once and you can attract the piranha to the area by sticking your fishing pole into the water and violently swishing it around. The noises are heard by fish closeby and they think it is a feeding frenzy, so they come to join in on the feast. You might want to try taking a feeder and cutting him with a knife, then swish him around in the water (using a pair of tongs or something, not your hands, lest you get bit). The fish would likely come to the table hungry this way. It may sound a bit greusome, but YOU are the one with the carniverous fish, not me. (yet!)