Fish with Human-Like Teeth are Found in Michigan
This is quite disturbing.
The Michigan DNR has confirmed that they have received three different reports of pacu fish. Two were found in St. Clair and another in the Port Huron area.
Pacu fish are found in South America and are known to have teeth that oddly resemble human teeth. Although they are non-native to the U.S. they don't pose a threat to the Michigan environment because being that they come from a warm climate, they cannot survive the state's cold weather.
However, the pacu is a popular aquarium fish and the DNR wants people to know to not throw your pet fish into Michigan waters. This includes pacu or even a goldfish. Instead:
...consider donating or trading it with another hobbyist, an environmental learning center, an aquarium or a zoo..."
You can even return it to the pet store where you purchased it and see if they'll take the fish back.
An aquarium fish has a small chance of survival if thrown into a body of water, such as a lake or river. And some of those that do survive, can spread diseases to the native animals in the water.
If you happen to catch a fish that's out of the norm - take a picture, put it on ice and contact Seth Herbst who is an aquatic invasive species biologist. Whatever you do... don't throw it back into the water.
More information can be found on the Michigan DNR website here.