Pacu: Freshwater Species of the Week

Pacu have teeth that look surprisingly human like. Photo: Julia Dorn/Courtesy National Geographic Channel


A few years ago I went snorkeling in a pair of crystal-clear streams in southwestern Brazil, in the Pantanal region. I got a close look at a toothy caiman (related to an alligator) and many species of fish, some brightly colored.

Plying the cool, clear waters of the Olho d’Agua (“eyes of water”) and Rio da Prata (“silver river”) were lots of pacu, which are prized by local indigenous people and fishermen for their meat. In fact, after my dip I enjoyed a dinner of fried pacu.

My guide told me that pacus are vegetarians, though they are related to piranhas, and do bare some resemblance, though pacus tend to be larger and can reach up to 55 pounds. Pacus also have teeth that bare a striking resemblance to human beings, as the above photo from the National Geographic Channel show Hooked demonstrates.

freshwater species of the weekMy guide mentioned that pacus dine on aquatic plants, snails, and nuts, which is why they have strong teeth…but he did not mention that some say they can inflict painful bites on people. While snorkeling, I marveled at the size of the pacus but didn’t fear them, instead keeping an eye out for caiman and anaconda. (No, they don’t have candiru in that part of Brazil. I asked.)

Pacus and piranahs both belong to the Characiformes order, like tetras. The name pacu is typically applied to a group of nine genera that share similar characteristics in body, diet, and behavior.

Pacu in America

This week, Huffington Post reported that a pacu was caught in Illinois, far north of its South American range.

The site reported, “Responding to a report that a fisherman had reeled in a piranha on June 7, lake superintendent Jim Caldwell brought the fish to the Illinois Department of Natural Resources, where it was identified as a pacu. Some reports say another pacu was seen a couple of weeks later.”

Huffington Post points to a story in the British Metro that claims pacu are known as “ball cutters” in Papua New Guinea. The fish were introduced there in 1994 to restock rivers that had been fished out of local species, but they are now invasive.

Metro claims two men were castrated, and killed, by pacus in New Guinea, although their source heard it second hand. The paper also called the large fish a “predator,” though it isn’t. A search online didn’t turn up any verifiable media reports of such deaths, so this reporter suggests taking that claim with a grain of salt.

In the Pantanal, locals said pacu are harmless.

No one is sure how the pacu ended up in Illinois, though game officials have said it was probably released from captivity.

Check out these photos I took of the fish in its native habitat in Brazil:

Photo: Pacu swimming in Bonito Brazil
Pacu swimming in Brazil in the Pantanal. Photo: Brian Clark Howard


Photo: Pacu fish swimming in Bonito, Brazil
A pacu emerges from the deep. Photo: Brian Clark Howard


Check out Huffington Post’s story on the pacu in Illinois >>

Check out 13 of the scariest freshwater species >>


Brian Clark Howard is an Environment Writer and Editor at National Geographic News. He previously served as an editor for TheDailyGreen.com and E/The Environmental Magazine, and has written for TheAtlantic.com, FastCompany.com, PopularMechanics.com, Yahoo!, MSN, Miller-McCune and elsewhere. He is the co-author of six books, including Geothermal HVACGreen Lighting and Build Your Own Small Wind Power System.

  • Julie

    Look at them chompers!

  • wolf

    I love animals.

  • Jonathan

    The show “River Monsters” has an episode covering this exact fish and discusses it at length as well as telling reasons for why the fish has those teeth(it eats nuts that fall off the trees in South America).

  • […] are flesh-eaters like the famous red-bellied species. Many are vegetarians—they’re known as pacu. And one species, called the wimple piranha, feeds only on fish scales. Silver piranha by David […]

  • James

    I bought a pair of red belly pacu back in the early 1990’s when they were the size of quarters. Years later, they had grown to over twenty inches in length, and approximately 4 inches in girth, and still growing. I, or should I say ‘they’ were fortunate that Steinhart Aquarium in San Francisco accepted them as a new addition to their 10 thousand gallon habitat with caymen, turtles, arrawanas, and other exotic Amazonian fish. My two pacus swam so majestically, and truth be told, I think they recognized my voice when I visited them on numerous occasions,

  • […] This swamp is part of the vast Pantanal wetland in central South America. The rich biodiversity in the Pantanal helps to make it one of the world’s most productive fisheries. (Related: Pacu: Freshwater Species of the Week.) […]

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