The pacu fish, a South American relative of the carnivorous piranha characterized by its distinct human-like teeth, has been showing up unexpectedly in Michigan lakes.
On Aug. 9, the Michigan Department of Natural Resources revealed that it has received reports of three pacu fishes found in two separate bodies of water in the state.
The red-bellied pacus (Piaractus brachypomus) are popularly kept as pets in home aquariums because of their unusual square teeth that look remarkably similar to those of humans.
Authorities said that the pacus found were likely introduced into the lakes by their former owners, who released them into the wild when they got too big for their aquariums at home, a practice that DNR's Aquatic Species and Regulatory Affairs Unit manager Nick Popoff described as "almost never humane."
Popoff said that pets from confined, artificial environments lack the ability to fight off and protect themselves from predators and may not be able to find food or shelter to survive.
While some of these former pets may make it in the wild, there is also the possibility that they will spread exotic diseases to the native animals or even reproduce in a manner that could eventually upset the natural ecosystem.
The pacu is a non-native fish but it is not considered invasive in Michigan because it is a tropical warm-water fish considered to have small chances of surviving the severe cold of Michigan winters. Invasive species are non-native species that can cause harm to the environment, economy or human health.
Pacus are vegetarians that use their human-like chompers to chew nuts, fruits and plants. This species of fish can grow up to 3 feet and weigh 55 pounds. Although the fish does not currently breed in the U.S. the DNR said that climate change may change this.
Paige Filice, who is connected with Reduce Invasive Pet and PLant Escapes, or RIPPLE, offers solutions for pet owners whose fishes have grown too big. He advised donating or trading the fish to another hobbyist, an aquarium, zoo or environmental learning center.
Pet owners may also check if the pet store where they purchased the fish would take it back. Another option is to discuss with pet retailers and veterinarians about humane ways to dispose of the pet.
Another reason not to dispose of these fishes in the wild is the legal repercussion.
"Invasive or not, planting fish of any kind in the waters of the state without a permit is illegal," said Popoff. "This includes the release of aquarium fish like pacus and goldfish, as well as farm-raised fish from private ponds."