Invasive Pend Oreille River pike originated in Cd'A chain lakes

A population of northern pike that is making its way down the Pend Oreille River to Lake Roosevelt has ties to a couple small lakes in Idaho, research shows.

Kellie Carim, an aquatic research biologist, has tracked the origins of a pike population spreading from Box Canyon Reservoir near Newport, Wash., to the northern end of Lake Roosevelt as having originated in the chain lakes of the Coeur d’Alene River.

The non-native northern pike has been designated as a prohibited species in Washington because of its potential to disrupt the Columbia River’s trout and salmon fishery and to impact efforts to restore native Columbia River salmon and steelhead stocks.

Northern pike were first reported in the Washington section of the Pend Oreille River around 2004, and for the next few years the fish became a popular target for anglers, but the voracious feeders were also seen as dangerous to native trout, salmon and preferred non-natives such as bass.

Despite an effort by the Washington Department of Fish and Wildlife and the Kalispel Tribe to reduce pike numbers in the Pend Oreille River system by about 90 percent — by using gillnetting, increased angler harvest and through pike derbies — the population continued to grow and migrate downstream.

Designating pike a prohibited species requires that anglers kill pike as soon as they are caught, and it makes transporting live pike illegal.

Dr. Carim, of the National Genomics Center for Wildlife and Fish Conservation in Missoula, was hired to find out where the pike came from in the first place.

“If they continue to come in through other sources, any efforts we place on suppression might be in vain,” Carim said.

Biologists had for years assumed the pike were washed into Pend Oreille Lake from Montana via the Clark Fork River. From there, it was assumed, the fish migrated down the Pend Oreille River into Washington, but Carim’s genetic research shows Idaho’s pike population mostly remains in Idaho’s portion of the Pend Oreille River downstream from Sandpoint.

“Lake Pend Oreille was not a primary source for fish in the river and in Lake Roosevelt,” Carim said.

In another scenario Carim investigated whether the Medicine and Cave lakes fish swam downstream from Lake Coeur d’Alene to the Spokane River, before migrating 200 miles upstream to Box Canyon. They would have had to navigate several dams in Washington and Canada. A prospect that seemed implausible, Carim said.

But the genetics didn’t add up.

“The pike in the Spokane River were not closely related to the Coeur d’Alene River drainage,” she said.

Additional evidence shows that although pike exist in the Spokane River’s Long Lake and near its confluence with Lake Roosevelt, northern pike aren’t spread throughout the Roosevelt system. Instead the fish appear again in the northern part of the lake, which supports the theory that the pike moved downstream from Box Canyon.

The likely conclusion is Washington anglers who caught pike in Medicine and Cave lakes near Medimont, carried them in buckets or live wells to Box Canyon where they were released.

“The data indicated the fish were moved, most likely by a person,” Carim said. “That’s the most likely explanation.”

More than 20,000 northern pike have been removed from Washington’s Pend Oreille river system using gillnets and last year the Colville Tribe placed a $10 bounty on the fish.

Northern pike aren’t indigenous west of the Rockies and North Idaho’s chain lakes population was introduced in the 1970s. Carim’s research uses fin clippings from pike in several lakes in Idaho that comprises a data set. Because the data set does not include fin clips from many lakes in which fish are present, including Hayden Lake, the question remains.

“What other population contributed to the invasion?” Carim said.