Mini Spotlight: Pacu

The handsome and misunderstood Pacu

Discriminating visitors to the South America Loop of The Reid Park Zoo will discover a small underground, underwater viewing area with a few happy turtles and some very large fish. These 2-foot creatures  seem ordinary enough, UNTIL one opens her mouth –  wait, those look like YOUR teeth! But don’t worry,  it’s natural for the peaceable Pacu.

Where do they come from?

Pacu are native to South America, living in permanent freshwater areas, like rivers or lakes (for example the Orinoco River) and also in temporary fresh water, like in floodplains or a flooded forests. Their favorite food is fruit, and especially the seeds inside – which is why those teeth of theirs come in so handy. They’re primarily herbivores, but may also eat small aquatic crustaceans and insects if necessary.

They spend most of their waking hours feeding, and if they live in a river, migrate upstream in order to spawn at the beginning of the wet season. They are amazingly adaptable to unfavorable conditions in their environment. For example, if oxygen levels in the water are depleted, they spend more time near the surface, they move more, and they protrude their lower lips. All these things allow them to use surface water in respiration.  

They don’t deserve the bad rap

It’s true that Pacu are pretty closely related to Piranha, which also live in freshwater sources in South America. But the Pacu are very different. First of all, they prefer to be solitary, and they don’t attack in huge, pointy-toothed groups like their infamous cousins.   And they only eat crustaceans when no delectable fruit is readily available – they don’t prefer them. So you shouldn’t be seeing them in any horrifying action movies.

But….I heard fishermen in TUCSON are finding them!

That’s true! One was recently caught in Silverbell Lake – but how did it get there?   Unfortunately, tiny Pacu are pretty cute, and often popular with people who like to keep aquatic pets – after all, they can say, “It’s kind of like a Piranha!” But those who sell the small Pacu either don’t know what they are, or are unaware that you need a permit to own one. The seller may also neglect to mention that very soon, the Pacu will reach 2 feet in length.  

So those jumbo adults are often released into local streams and lakes across the country. And they’re adaptable – so can quickly become an invasive species. In addition to shocking humans who encounter their toothy grins, they can also upset an ecosystem by competing with native species for the same food sources. Tucson Game and Fish spokesman Mark Hart hopes that if you do have a Pacu and can no longer take care of it, you will return it to the pet store! How about just going to see them at The Reid Park Zoo? 


Leave a Comment

  1. What an interesting article. I had no idea these fish were being found in local lakes and ponds–how irresponsible! I hope people will think twice about choosing wildlife for pets; not a good idea. Thank you for that information about their swimming/breathing near the surface for better exchange of oxygen.


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