Oregon Department of Fish and Wildlife

In the cool waters of Diamond Lake in Douglas County, anglers can fish for rainbow trout surrounded by the beauty of Diamond Peak and the encompassing forest.

At a location near Ontario accessible by car, entry-level anglers can find easy fishing success thanks to a schooling bluegill population.

And in the mountainous areas of Central Oregon, fisheries for kokanee, brown trout and rainbow trout are alive and well in Paulina and East lakes, part of the Newberry Crater.

Yet these fisheries and many others like them throughout Oregon are always at risk from what’s sometimes called “bucket biology,” state biologists say.

Invasive species introduced to the lakes and reservoirs can change fish populations.

Whether left behind by individuals who dump leftover live bait into the water, not realizing the harm, or by others who want to change the fishing grounds themselves, bucket biology is harmful to fisheries. It’s disappointing for anglers who count on getting a good catch at their favorite lakes. It’s also illegal with a hefty fine for those who are caught.

“Most introductions do not take, from what we understand, but when they do take, they can be pretty catastrophic,” said Mike Harrington, interim deputy director for Fish and Wildlife programs at the Oregon Department of Fish and Wildlife (ODFW).

Taking over

Fish that aren’t meant to be in a lake can compete with those that are either native to the area or native-compatible fish stocked by ODFW.

Stocked fish are chosen because they thrive in that particular climate, provide a good catching experience and are what the majority of people want, regional fish biologists said.

Invasive fish may eat the same food source eaten by the stocked fish, causing stocked fish to suffer from low growth and poor quality.

“We were able to show that … relative weight was very low in those lakes where we had those illegal introductions,” Harrington said, including in Walton Lake and Antelope Flat Reservoir in the Ochoco National Forest.

Illegal introductions also can wreak havoc on the habitat, stirring up sediment at the bottom of the lake and muddying the water.

That’s what happened in Ontario at Beck-Kiwanis Pond, which is stocked with largemouth bass and bluegill, and then rainbow trout in the winter.

Carp and goldfish that were illegally introduced look for their food in the sediment, stirring up the pond in the process, said Dave Banks, district fish biologist in the Malheur Watershed District.

“It’s a game of attrition. Once you get those species in there, it’s only a matter of time before they take over a pond,” Banks said.

For the complete story, see the June 30 edition of The Observer.