Oregon Wildlife Officials Say Someone Dumped Possibly Invasive Koi into Eugene River

Published 12/20/24 at 8:25 a.m.
By Oregon Coast Beach Connection Staff

(Eugene, Oregon) – Oregon Department of Fish and Wildlife (ODFW) is concerned about a find of possible invasive species in a river near Eugene, after someone apparently intentionally dropped koi into the water. (Photo ODFW)

ODFW said staff responded to the Armitage Boat Landing on the McKenzie River on Wednesday, December 18, after getting a call on their Oregon Invasive Species Hotline about the fish.

District fish biologists successfully removed the large koi from the waters on the northern edges of Eugene (about 60 miles from the Oregon coast). However, they are worried about the potential impact of koi, which can be considered an invasive species in the wild – even if perfectly acceptable as pets. ODFW said koi fish can live up to 25 years, reproduce rapidly, and endure very cold winters. They can produce between 5,000 to 10,000 eggs, with the largest koi capable of laying up to 500,000 eggs.

Jeff Ziller, ODFW District Fish Biologist, highlighted the risks associated with non-native fish. "Introduced, non-native fish can spread deadly diseases to wild fish populations," Ziller said. "In many states and countries, koi have altered aquatic ecosystems extensively, leading to significant public resource allocation for their eradication, often with little success."

Koi are omnivores with a voracious appetite, consuming fish and amphibian eggs, aquatic insects, and competing with native fish for food. They also disturb sediments while uprooting and consuming aquatic plants, which can reduce forage and cover for waterfowl and other animals.

ODFW urges the public to avoid dumping unwanted fish or aquarium contents into waterways, as non-native species are nearly impossible to remove once introduced. This practice can have serious ecological consequences and ruin recreational opportunities for future generations.

Once non-native species are introduced to a waterbody, they are nearly impossible to remove.

“Help spread the word to never dump unwanted fish or aquarium contents in or near waterways, streams, ponds, lakes, or stormwater drains,” ODFW said. “It can have serious ecological consequences and can ruin recreational opportunities for future generations of Oregonians.”

ODFW staff appreciate the report to the Invasive Species Hotline. Non-native, invasive species, such as koi, can be reported to the hotline at 1-866-INVADER.

In 2011 and 2012, Oregon coast officials had run-ins with a possible inundation of invasive species, after the tsunami in Japan in March of 2011 brought a large array of life-covered debris. At last count, over 200 species of sea creatures had been discovered – still alive – on the objects shuffled across the Pacific.

However, in 2016, researchers from OSU in Corvallis and the Hatfield Marine Science Center in Newport said it was likely the region has “dodged the bullet,” as one scientist put it.

Tsunami dock in Newport, 2011 (Oregon Coast Beach Connection)

John Chapman, an Oregon State University expert on tsunami debris said they had not found populations of non-native species firmly established just beyond the breakers.

More threatening was the concrete dock that arrived in Newport in 2012, coming from Misawa, Japan. That arrived with nearly 200 different species on it, including varying kinds of mollusks, sea stars, oysters, amphipods, barnacles and worms. Some were open water creatures that had hitched a ride along the way and presented no threat. Others were definitely not from around here and could wreak havoc with the ecosystems of the Oregon coast near-shore environment - perhaps even the tide pools much beloved by visitors.

Tsunami dock in Newport, 2011 (Oregon Coast Beach Connection)

Chapman said his team was “blown away” by the find.

“We had always thought these organisms would not be able to survive the long trip across the Pacific Ocean, the middle of which is a biological desert,” Chapman said. “Yet here they were.”

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Andre' GW Hagestedt is editor, owner and primary photographer / videographer of Oregon Coast Beach Connection, an online publication that sees over 1 million pageviews per month. He is also author of several books about the coast.

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