BURNS -- Say what you will about the invasive common carp in Malheur National Wildlife Refuge. They're ugly. Unappetizing. A bane on the Eastern Oregon ecosystem.
But don't say they're not resilient.
Managers at the migratory bird sanctuary south of Burns have tried dynamite. They've tried poison. They've tried suffocating the fish by draining water from lakes and ponds. They've put screens across waterways to keep the carp from finding new territory.
None offered more than a temporary respite from an invasion that has plagued Malheur Lake and nearby waterways for nearly a century.
"Every time, it would be two, three, maybe four years before they'd repopulate," refuge manager Chad Karges said. "They're the perfect invasive species. There's very little that will kill them."
The carp have created an ecosystem so out of balance it no longer supports the plant and insect life birds rely upon for food and habitat. Populations of migrating ducks, geese and shorebirds that once passed through the refuge in numbers as great as half-a-million each day have dwindled to a tenth that size.
Now, refuge bosses hope to wrest control with fishing nets.
They've partnered with the Oregon Wildlife Heritage Foundation and the owner of Pacific Foods, a Tualatin company best known for boxed soup and soymilk, to stage a massive commercial fishing operation on the refuge.
The five-year contract began this year, but drought kept lake waters too low to start fishing. But by spring 2016, the team hopes to begin removing thousands of fish from the water each day.
If all goes well, as many as 4 million pounds of carp could come out of the lake next year. The meat, which most Americans won't eat, will be used to fertilize Chuck Eggert's crops.
Eggert, who owns Pacific Foods, has formed a side company, Silver Sage Fisheries, to acquire and process the castaway carp. Once taken from the lake, the carcasses will be trucked to Burns for processing before being spread across alfalfa fields that feed Eggert's dairy cows.
"It's been enjoyable to get a broader partnership going to address what has become a longstanding issue, while putting the waste to use," said Tim Greseth, the executive director of Oregon Wildlife Heritage Foundation, who worked with Eggert to develop the fertilizer concept.
Unlike past carp control efforts, the goal this time isn't to eradicate the fish. Instead, workers hope to remove enough carp to trigger an "ecological tipping point," loosening their stranglehold so plants and insects can rebound, once again providing enough food for the millions of birds that historically have rested here during their migrations.
Organizers hope a few years of intensive fishing will do the job. In subsequent years, lighter maintenance fishing should keep the fish at bay.
"We're trying for a more sustainable carp control, instead of the shotgun approach," said Linda Beck, the refuge's fish biologist.
The refuge has always been one of the West's most crucial migratory stopovers. The carp problems notwithstanding, its significance has grown in recent years as development has gobbled up wetlands and drought has squeezed water supplies at other refuges, including those in the Klamath Basin complex.
"Our ability to restore some of Malheur Lake is becoming more important in the grand scheme," Karges said.
The team expects this to be the largest common carp control effort ever attempted, although no official numbers are kept on the topic.
The fish began turning up on the refuge in the 1920s, but how they got here is up for debate. Some say a landowner stocked them as a food source. Others say the carp were used for vegetation control.
By the 1950s, they were a problem. Today, the olive-colored bottomfeeders are spread so thick in the shallow Malheur Lake, their exposed back fins create the illusion of windblown ripples on the water.
During a recent airboat ride across the lake, Beck estimated there were as many as 10 million adult carp living here and in connected waterways.
"This is the biggest pod I've ever seen," she said as she cut the engine. The fish emitted soft thuds as they collided with the boat.
Each female can lay more than a million eggs in a single year. As the fish multiply, the birds disappear.
The carp's constant rooting along the lake bottom has clouded the waters, denying aquatic plants the sunlight they need to photosynthesize. Over time, once clear water filled with cattails and marsh grasses has become an enormous mud puddle, barren of biodiversity.
Without the plants, the birds have nowhere to nest or hunt for food.
The carp, which can survive in extreme conditions and are not picky eaters, have also pushed other finned species out of the equation. Beck and her team have taken thousands of samples and found only a handful of fish that aren't carp.
"There should be an awesome mosaic of life here," she says. "We want to get that back."
Whether commercial fishing can achieve that goal remains to be seen.
Similar efforts have found success in the carp-infested Mississippi River and its tributaries. But Greseth said commercial fishing has never been used to combat invasive species on this scale.
"This first year, we're going to be working a lot of the wrinkles out," he said. "How to fish under the conditions in Malheur Lake, understanding where they're breeding ... there's going to be a lot of back-and-forth information sharing."
While the fishermen work to reduce the lake's carp population, refuge workers are experimenting with tactics to stop the next generation from hatching.
There's promise in a system that aborts carp eggs by shocking them with electrical currents. Beck said recent tests of the system succeeded. After mapping the fishes' preferred spawning grounds, refuge workers could employ the shock treatment on targeted sites in the future.
If the team can remove enough carp to get some plants and birds back, predators such as brown bullhead, terns and pelicans could lend an additional hand to the carp control efforts by eating juvenile fish.
"If you can get the total population under some control, a lot of the natural mechanisms will help take care of the rest," Greseth said.
-- Kelly House
khouse@oregonian.com
503-221-8178
@Kelly_M_House