The Oregon Department of Fish and Wildlife has removed an invasive koi fish from the McKenzie River near Eugene.

The fish was fish spotted Dec. 18 near the Armitage Boat Landing. The large koi was most likely intentionally released into the McKenzie River, said Oregon Department of Fish and Wildlife fish biologist Jeff Ziller.

“It was a very obvious, bright orange football-sized fish,” said Ziller, adding that it was “two to three pounds” and was euthanized. The fish will be opened up to determine if it is male or female.

Koi rescue clubs take abandoned koi but Ziller said the fish biologists did not have access to the groups when the fish was found on Thursday night. Euthanizing the fish was the best option, he said.

“We have no idea what diseases it may have carried or where it came from, it was best to take it out of the river and remove any possibility of infection,” he said.

Whether the fish was dumped alone or with other koi is not known, said Ziller.

Koi are not a natural fish. They are an ornamental variety of the common carp. For centuries carp were farmed in rural areas of Japan before ornamental Amur carp breeding began in the 1820s on the northeastern coast of Honshu. Today they are sold as aquatic pets around the world.

Koi can live up to 25 years, reproduce rapidly and can survive very cold winters. Mature koi can produce 5,000 to 10,000 eggs, the largest koi can lay 500,000 eggs.

The danger of koi fish spreading disease is real and there are examples of them damaging ecosystems in a number of countries. Efforts to eradicate them are often expensive and unsuccessful.

Koi are omnivores with a big appetite. They consume other fish, amphibian eggs and aquatic insects, usually outcompeting native fish for food. They also stir up sediments while uprooting and consuming plants, which can reduce forage and cover for waterfowl and other animals.

Abandoned koi have established a presence in Cottage Grove Reservoir and Ziller says there are few things that can be done to remove them.

The Oregon Department of Fish and Wildlife urges the public to avoid dumping unwanted fish or aquarium contents into or near waterways, streams, ponds, lakes or stormwater drains. Doing so can have serious ecological consequences and can ruin recreational opportunities for future Oregonians, the department said.

“There are options out there, koi rescue clubs. That is what we hope to get out to the public, if you have fish you can’t deal with, find someone that can take them because they can cause all kinds of problems in waterways,” said Ziller.

To report invasive species, contact the invasive species hotline at 866-468-2337 (866-INVADER).

For individuals with unwanted koi wanting a safe place to take them, contact the Oregon Koi and Watergarden Society.