Piranhas: How Dangerous Are They?

The Piranha: Interesting Fish But Not a Good Choice for a Community Aquarium

Red Bellied Piranha
Red Bellied Piranha. Gonzalo Rivero

Adventure movies are filled with scenes of people being stripped the bone in seconds by ravenous piranhas in jungle streams. But piranhas are also kept by some people as specimens in home aquariums. So what is the reality? Are piranhas dangerous, and if so, just how dangerous?

Of more than 20 piranha species, it is the red-bellied piranha that is the subject of most of these legends. And it is true that attacks on humans have occurred, mostly in the Amazon basin. There are several hundred documented cases of attack, some ending in death.

According to one study, piranha attacks tend to peak in the dry season when food is scarce and water levels are low, which leads to heavier-than-usual concentrations of fish. But fatal attacks are quite rare; attacks are normally limited to small but painful nips to the hands and feet. The fish does have powerful jaws and sharp teeth and is a formidable predator--but to other fish, not humans. 

The fact is that hungry piranha will bite almost anything, even other piranhas. However, piranha normally feasts on other species of fish or wounded animals--not humans. In fact, more piranhas are eaten by people then people are eaten by piranhas.

How Dangerous Are They?

Fish expert Dr. Axelrod once stated on network television that piranhas are not dangerous to people. Later he was dared to prove it, and prove it he did--by wading into piranha-infested waters wearing only swim trunks. Placing a large piece of meat on a fishhook, he dangled it in the water and waited to see what happened. The piranha tore into the meat but not Dr. Axelrod.

Are Piranhas Legal?

Even though piranhas are not really endangering humans, they do present a danger to native fish. For that reason, many states restrict importing, breeding or even keeping them in aquariums. Why? Because unfortunately, people have, and will, dump fish they don't want into rivers or lakes. A piranha tossed into river or lake can easily disrupt fish species that are supposed to live there, thus damaging the ecology. The potential for a breeding population becoming established in our waters is a possibility, and for this reason, some states choose to ban the fish even for use in indoor aquariums. 

Should You Keep Them?

Even if they are legal, piranhas are not an ideal aquarium fish. They can't be kept with other fish because they are natural predators and will eat other species and sometimes even others of their own kind. Piranhas are also reclusive, and unless your tank is empty of all cover you won't see them out and about often. They are rather skittish and hide a good deal of the time. Feeding time is when you will see the most action, and even then they may wait for you to leave the room before they feed.

If you are serious about wanting to keep piranha, study what they need to stay healthy. Piranhas are carnivores that prefer their food live. They need a quiet habitat with places to hide, and should not be kept with other fish, even their own species. Because of the danger they present to local habitats, piranhas are not legal in many states, so check your local laws before trying to bring one home.