Field Notes: Don't Let Them Go
Don't Let Them Go
Minnesota will never be confused with the tropics. But that hasn't kept creatures from South America, Africa, and other warm climates from appearing in the state and raising concerns among biologists.
This past fall, for example, a pair of Brooklyn Park anglers captured a 2-foot-long caiman in the Mississippi River under the Interstate 694 bridge. Caimans, crocodilelike creatures, range from southern Mexico to Brazil's Amazon River basin.
The caiman, which was eventually turned over to a reptile expert, was likely an aquarium pet that had been illegally dumped by its owner, said DNR invasive species biologist Nick Proulx.
Although many nonnative animals and plants won't survive Minnesota's climate, releasing them into lakes and rivers is risky for several reasons, Proulx said. They could introduce diseases or parasites or have invasive species hitchhiking on them. Some released species and hitch-hikers that survive and become invasive can increase in abundance and displace native species. Ornamental purple loosestrife, for instance, invaded Minnesota waters.
In recent years the DNR has confirmed angler catches of red pacu in the Mississippi River and Tanners Lake east of the Twin Cities. Native to the Amazon basin, these popular aquarium fish resemble piranha but eat fruits and vegetation.
Nonnative water-garden plants have turned up in Minnesota waters. Water hyacinth (Eichhornia crassipes), a free-floating flowering plant from Brazil, has been confirmed in lakes and ponds in Chisago and Ramsey counties. Water lettuce (Pistia stratiotes), a perennial of Africa, was found in Lake Winona.
Such discoveries-as well as news reports of aggressive snakehead fish, native to China, turning up in Wisconsin, Maryland, and Florida-have heightened awareness of illegal releases of nonnative fish and aquatic plants into the wild.
Preventing releases of nonnative species that could be as invasive as purple loosestrife (Lythrum salicaria) or Eurasian watermilfoil (Myriophyllum spicatum)-once used in aquariums-is a high priority for the DNR. Other concerned agencies and businesses are working to give aquarium hobbyists and water gardeners an important message: Do not release aquarium fish and water plants in any lakes, rivers, or other waters. The U.S. Fish and Wildlife Service, the Pet Industry Joint Advisory Council, and the Great Lakes Sea Grant Network have developed a nationwide campaign known as HabitatTitude to raise public awareness.
The DNR and the Habitattitude campaign recommend alternatives to releasing unwanted fish and plants in any waters:
- Seal aquatic plants in plastic bags and dispose in the trash.
- Contact a retailer for advice on proper handling or returns.
- Give or trade with another pet owner or water gardener.
- Donate to a local aquarium, school, or aquatic business.
- Contact a veterinarian or pet retailer for guidance on humane disposal of animals.
DNR Invasive Species Program coordinator