Why Are Vegetarian Piranhas Turning Up in Michigan?


Imagine enjoying a nice swim in Lake Erie on a summer afternoon. The water is cool. You are with friends and family. All is right with the world. Until you see a horrible sight swimming toward you…a piranha. You panic and try to swim away as fast as you can. There is no real danger, though. This piranha is a vegetarian. Which begs the question: why are vegetarian piranhas turning up in Michigan?

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Are They Really Piranhas?

Most everyone has seen a picture of a piranha before. People have shared awful stories of what happens if you encounter the fish in the wild. They strike fear into the hearts of all who see them. They make their homes in South America, occupying the many lakes, rivers, reservoirs, and floodplains. However, there are many species closely related to the piranha. They differ greatly but some are not even carnivores.

“Piranhas” found in Michigan today are not actually piranhas at all. They are close cousins known as pacus. The pacu lives in the same environments as other piranhas, inhabiting freshwaters in South America. Yet, they are omnivores. They subsist mainly on vegetables and tree nuts that fall into the water. Their diet requires that they have teeth. Unlike their more dangerous relatives, pacus have square teeth. In fact, the teeth closely resemble those a human being.

The differences don’t stop there. Younger specimens are often mistaken for piranhas because of their similar size. Once fully developed, though, pacus dwarf the other species. Adult pacus can reach lengths of over three feet and weigh up to 90 pounds.

Why Are They in Michigan?

Pacus are commonly purchased by aquarists seeking exotic species. Owners enjoy the novelty of a species with as strange a features as humanoid teeth. Most make responsive pets with the right commitment and training. Fish are typically purchased when they are young, though. When at their smallest, the fish is easily managed. These fish lovers underestimate how aggressively the species grows. Most modest aquariums don’t cater to the sheer size of a developed pacu. Instead of donating them, these pet owners decide to release the fish into the wild.

While not suited for surviving the cold, harsh winters of the Great Lakes, there are fears that the pacu could find its way to warmer waters in the United States. Twenty six other states and Puerto Rico have reported catching the fish in the wild. People have also caught specimens have across Europe, Asia, and in New Guineau.

Releasing non-native species into ecosystems can wreak havoc on indigenous wildlife. The Michigan Department of Natural Resources explained that, while the pacu may not have huge environmental effects, other species do. Even something as innocuous as the common goldfish can change the way that populations evolve. These simple fish have started reproducing at an alarming rate across the Great Lakes.

How do you feel about having piranha-like creatures swimming in the Great Lakes? Do you think that releasing fish into the wild is a safe practice? Do you think that it could harm local wildlife populations? Let us know your thoughts.

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