What is a pacu fish's predators/dangers

he Piranha is one of the most efficient predators on the face of the earth. Granted it is not a large animal, with most only reaching about 5 1/2 to 10 inches (14 – 26 cm), but it is known world wide for its ferocious nature. They have razor sharp teeth and are opportunistic carnivores.

A frenzied attack by a group of Piranha will set the water churning. They will attack and eat all sorts of aquatic animals, insects, lizards and amphibians. They will also devour rodents, carrion (dead meat), and sickly or weakened land animals that venture into the water.

The teeth of the Piranha are triangular in shape with an exact fit in their jaw, comparable to a bear-trap. They are designed to puncture and slice the flesh from their prey. They can strip their prey to the bone in a matter of minutes.

These fish are a great source of fascination. Their natural behaviors have become fodder for the scripts of moviemakers looking for a sensational twist to excite and entice an audience. What could be more intriguing than creating a 'fear factor' from the behaviors of these provocative fish found in the "wild". Yet just like the Great White Shark and the Anaconda constrictor, also popular subjects of thriller movies, the Piranha’s behaviors are over-fantasized.

The Piranha does engage in a feeding frenzy that will "make the water boil" if only because a hungry school of fish are trying to reach the same limited food source. All that activity is bound to create water turbulence. A Piranha school generally only consists of about 20 or so fish, but in a feeding frenzy it can reach up to several hundred..

Piranhas are not always that deadly. Many species live solitary lives once they reach maturity and only four or five species pose any significant danger. Piranhas rarely attack people. Many experts believe they are actually timid fish, and shoal for protection. Even the most aggressive are thought to be not really dangerous until they are trapped and confined, and then attack in self defense. As a pet they are fascinating and beautiful fish, yet you can't hold or pet them. They are not affectionate and owners must be extremely careful, especially when handling them. They do have sharp teeth and an aggressive/defensive nature. Most Piranha bites are sustained when the fish are being handled, though that's not to say a hungry fish is never dangerous.

it would lead to upper respiratory infections and pneumonia.

digestion

it excretes wastes