For the PUDs that operate the five mid-Columbia River dams, salmon survival along the 143-mile stretch of river is a balancing act requiring no net impact on ESA-listed salmon and steelhead passing through their projects.
Salmon losses—both at the dams and in reservoirs—are mitigated by producing fish in hatcheries, and by other actions, like managing predators and restoring habitat.
Fisheries scientists from Chelan, Grant and Douglas county PUDs explained their salmon and steelhead passage strategy in a Feb. 10 presentation to the Northwest Power and Conservation Council.
Lance Keller, senior fisheries biologist for Chelan PUD, said that unlike the U.S. Army Corps of Engineers, the PUDs measure survival throughout the entire project area, including the reservoirs, dams and tailraces.
Each PUD has its own long-term agreement for ensuring survival, which considers losses from passage structures and from reservoir or tailrace impacts such as predation from birds and other fish. "We have to measure across the entire project area," Keller said.
He said the five dams, reservoirs and tailraces encompass a total of 143 river miles, starting below Priest Rapids Dam and extending to above Wells Dam.
Chelan and Douglas PUDs operate under habitat conservation plans, and Grant PUD has a salmon and steelhead settlement agreement.
"We do view these survival standards as the most comprehensive in the Columbia Basin," Keller said. Each PUD measures its own survival rates through each reservoir, dam and tailrace, aiming for a smolt survival rate of 93 percent at each project, and a 91 percent survival rate when combining adult and juvenile survival.
Depending on the combined passage rates, the PUDs mitigate for as much as a 9 percent loss of both ESA-listed and nonlisted fish. Through the agreements, the PUDs commit 2 percent toward tributary improvements, while the remainder—up to 7 percent—goes to fund hatchery production. Every 10 years, the number for hatchery fish production is recalculated based on smolt survival and adult returns. The PUDs expect to begin the process of recalculating hatchery production this year, Tom Kahler, Douglas PUD fisheries biologist, told the Council.
Peter Graf, Grant PUD fisheries scientist, said hatchery production is one of the pillars of his utility's no-net-impact standard.
The Mid-C PUDs own or help support a couple dozen hatcheries that produce more than 10 million juveniles, including spring, summer and fall Chinook, sockeye, steelhead and coho. Those that return as adults either contribute to the natural spawning fish or offer harvest opportunities.
"Our hatcheries are very effective at producing returning adults," Graf said, noting that mid-Columbia hatchery fish are much more successful than wild fish when it comes to returning adults, and smolt-to-adult return rates.
He said for every summer Chinook collected for broodstock from the Okanogan River, 22 fish are later harvested as adults in the ocean, or by tribal or nontribal fishers on the river. For each fall Chinook collected for broodstock in the Hanford Reach, 11 fish are later harvested as adults, he added.
"This is a massive contribution, and it helps support the fisheries," he said.
Hatcheries can also help wild fish at the end of their life cycle, before spawning, Graf said. He noted the Independent Scientific Advisory Board's 2018 review of spring Chinook salmon in the upper Columbia River described high adult survival through the Mid-C projects, but significant pre-spawn mortality, when adult fish die in their native rivers before spawning. Graf noted that because spring Chinook are the earliest to return, they hold in the Wenatchee River for two to three months between July and September, when nearly half of those that made it back die. "This is a huge loss, and it's right at the finish line," he said.
He said it's unknown why, but warm water temperatures and high numbers of hatchery fish could be contributing to the mortality rates. To help boost wild Chinooks chances of making it to spawning, the PUD collects some adults in the Wenatchee River and holds them in a hatchery until spawning. Graf said about 98 percent of those collected and held make it to spawning. "To me, it indicates these fish are capable. They have the energy reserves to make it, if they have the habitat to support them," he said.
The PUDs have also contributed more than $58 million to help fund more than 200 habitat projects over the past 16 years, according to the PUD presentation.
One example is a long-term program to reintroduce sockeye to Skaha and Okanagan lakes in British Columbia, in which the PUDs worked with Canadian First Nations and agencies to help develop and fund a new water management tool, a $4.5 million Penticton Hatchery and the reintroduction program that brought sockeye back to this region.
Douglas PUD's Kahler said the McIntyre Dam on the Okanagan River in Canada had completely blocked sockeye from reaching three large lakes where they once spawned. Okanagan sockeye were greatly affected by the loss of this traditional spawning and rearing habitat, he said. Modifications at the dam and other habitat improvements allowed for both adult and juvenile passage, opening access to these lakes.
The reintroduction program now releases millions of sockeye fry from the hatchery into Skaha and Okanagan lakes. The number of sockeye passing Wells Dam each year jumped from an average of about 30,000 from 1977 through 2007, to nearly 200,000 a year since 2008, the presentation shows.
The sockeye reintroduction is an example of the geographic extent that Mid-C PUD programs reach, Kahler noted.