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Today on Animal Fact Files we’re discussing pacus. There are many species commonly referred to as a pacu, like the giant pacu and the red-bellied pacu, but their classification has changed a lot with genetic research, so there isn't one specific group of fish known as "the" pacus. That being said, you may have noticed these fish look quite similar to another, more well-known fish: piranhas. In fact, pacus and piranhas are related.

Like piranhas, pacus live in freshwater rivers and flooded forests of South America. Most pacus can't tolerate temperatures below 60 degrees (15*c) so they're considered truly tropical fish. In size, pacus can vastly outgrown piranhas. Some species, like the large black pacu, can reach as long as three feet (91cm) though on average they're a bit smaller. Others max out at just under half this length, but that still makes them bigger than the foot-long (30.5cm) piranhas. Pacus can also weigh over forty pounds (18kg) which is ten times the weight of the average piranha, but smaller species exist that are approximately the same size as piranhas.

Some pacu species actually look like their relatives. For example, the red-bellied pacu turns bright red along its belly during the spawning season, mimicking the red-bellied piranha. This makes them difficult to distinguish from the more aggressive piranha. Pacus also have teeth, but not scissor-sharp slicers like piranhas. In fact, pacu teeth are described as human-like. They're large and used to crush their favorite meals: nuts and fruit.

Yes, the pacu largely prefers a planet-based diet. While they will take invertebrates and small fish, especially when they're young, pacus generally dine on seeds, fruits, and nuts that fall into the water. The splash alerts them to a potential meal and they make their way over to investigate. Pacus are able to break open hard food items, like palm nuts and rubber tree seeds that other fish don't have access to, so this gives the pacu an edge over the other fish in the area. Many pacu adults eat lots of food during the wet season to build up fat and then basically starve during the dry season. During this time, flooded forests all but dry up to fragmented pools in which the adults live until the rains return. Thankfully for them they can survive in low oxygen water by skimming oxygen off the water's surface.

Pacus generally have an overbite or just a slight underbite when compared to the piranha's distinct underbite. The layout of their jaws helps them more easily access the water's surface for oxygen and provides for easy chomping on meals. It takes anywhere from two to five years for pacus to reach reproductive maturity depending on the species, and they can live to be more than a decade old.

Like the piranha, who is shrouded in myths about their ferocity, the pacu comes with its own widespread non-truth. In what started as a joke, pacus are believed to bite human testicles if they live where people are swimming. The idea was that the fish would confuse the nuts they eat with the… well you get the idea. This was all a misunderstanding, however, and there are no records of this actually occurring.  

For more facts on pacus, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!