The Oregon Department of Fish and Wildlife has been taking lots of calls from the Cottage Grove reservoir lately.
Anglers are seeing hundreds of ornamental koi swimming around.
These colorful, non-native fish can wreak havoc on local water systems.
Koi are colorful variants of carp, originally bred in Central Europe and Asia.
They’re sold as aquatic pets all over the world.
A large, adult koi can lay up to 500,000 eggs.
They are omnivores with voracious appetites, often depriving native fish of food.
ODFW Fish Biologist Jeremy Romer has a pretty good idea of how the koi got into the reservoir.
"People love to have them in their ponds as something to look at," he said.
"And then, they overpopulate those ponds and they’re not sure what to do with them.
And so often, they don’t have the heart to euthanize them.
So, they just take a bunch of them and go release them into our state water bodies which causes a lot of problems.”
Romer said ODFW wants to prevent these types of releases because once they do get into a large water body like Cottage Grove Reservoir, they’re nearly impossible to remove.
"These fish also have potential to spread diseases and they survive really well through the cold winters,” Romer said.
ODFW conducted an extensive boat electro-fishing survey in 2018 and no koi were encountered at that time.
In recent weeks, big schools of koi have been sighted by anglers, but few have managed to pull any out.
Tyler Fredrickson is an exception.
Photo courtesy of Tyler Fredrickson
As Fredrickson and his family were visiting the reservoir to take photos, Fredrickson saw a bright fish in the sparkling water and grabbed his fishing rod.
After a struggle, the angler pulled in a huge, colorful koi.
And out of the lake it stayed.
If a koi is caught at Cottage Grove lake, Romer urged anglers not release it alive.
And he added, never dump unwanted fish, bait or aquarium contents in or near water bodies or drains.