The vegetarian piranha relative that is turning up in rivers across the globe
In short: Often sold as small, docile aquarium pets, pacu are actually powerful, large-growing fish with crushing jaws. When owners realize they cannot maintain these giants, they often illegally release them into local waterways. From Europe to North America, these invasive fish are now appearing in unexpected and distant environments.
Pacu are a group of omnivorous freshwater fish native to South American basins like the Amazon and Orinoco. While they are closely related to piranhas, they differ significantly in anatomy and behavior. Unlike the razor-sharp, underbitten piranha, pacu possess straighter, squarer teeth designed for crushing seeds and nuts. They can reach impressive sizes, growing up to 1.08 meters in length and weighing as much as 40 kilograms.
The popularity of pacu in the global aquarium trade has led to their widespread introduction outside their native range. Because they are often sold as small juveniles without adequate warnings about their growth potential, overwhelmed hobbyists frequently release them into wild ponds and rivers. While most are unlikely to survive long-term in colder climates, they have become established in tropical regions of Asia and parts of Puerto Rico. In places like the Sepik River in Papua New Guinea, their introduction has caused ecological damage by outcompeting native species and consuming vital vegetation.
Beyond their ecological impact, pacu are prized as food fish in South America and are increasingly farmed globally due to their ability to thrive in low-oxygen water. However, their powerful jaws remain a hazard to humans. While media reports once jokingly suggested they targeted human anatomy, the reality is more practical: their crushing bite is strong enough to cause traumatic injuries to fingers. As a result, experts advise that even aquarium-raised specimens should be handled with caution, and authorities strictly prohibit releasing them into the wild.
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Sources
- Summary by Intellect · source: Pacu
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