The Michigan Department of Natural Resources (DNR) recently reported finding fish with “human-like teeth” in southeastern Michigan lakes. Anglers spotted red-bellied pacu in Lake St. Clair and near Port Huron. While the sight of these unusual fish may be good for a giggle or a gasp, their presence in Michigan lakes points to a deeper issue.

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These unusual fish sport teeth eerily reminiscent of humans’ so they can eat seeds and nuts. While they’re not native to Michigan, DNR said they’re not invasive. They’re imported from South America, and their presence in Michigan lakes likely means aquarium owners dumped their pet fish into the lakes.

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The DNR took the opportunity to remind aquarium owners it’s illegal to release their fish without a permit, and that pet release of any kind is rarely the humane option. Aquatic Species and Regulatory Affairs Unit manager Nick Popoff said in a press release, “Pets released from confined, artificial environments are poorly equipped to fend off predators and may be unable to successfully forage for food or find shelter. Those that do succeed in the wild can spread exotic diseases to native animals. In the worst-case scenario, released animals can thrive and reproduce, upsetting natural ecosystems to the degree that these former pets become invasive species.”

In the wild, the pacus probably wouldn’t survive frigid Michigan winters, but DNR said climate change could “increase the possibility” of their survival through the winter.

The pacus may have been dumped because they outgrew their tanks or started to eat other aquarium fish, said Paige Filice, who works with the Reduce Invasive Pet and PLant Escapes (RIPPLE). She suggested that rather than dumping the fish in lakes, pacu owners could donate their fish to a zoo, aquarium, environmental learning center, or another hobbyist. She said some pet stores might take the fish back if an owner can no longer care for the pacu.

+ Michigan Department of Natural Resources

Images via Michigan Department of Natural Resources, Henrik Carl, Natural History Museum of Denmark, and Wikimedia Commons