The Idaho Department of Fish and Game’s assistant Fisheries Bureau chief last week gave the Northwest Power and Conservation Council a “gravel to gravel” update regarding his agency’s Snake River Sockeye Salmon Captive Broodstock program.
First of all, the number of adult fish returning this year to the spawning gravels in Redfish Lake in central Idaho’s Sawtooth basin is the highest it’s been since the early 1950s. Through Sept. 29 a total of 1,316 sockeye had returned to the basin and all but 100 -- which were captured and scheduled to be spawned at Eagle Hatchery to fuel the broodstock program -- made it to the lake to spawn in the wild.
Of the 2,201 adult sockeye counted at Lower Granite Dam this year, 1,316 or 60 percent have been accounted for in central Idaho. That “conversion rate” matches the annual average over the course of the broodstock program -- about 60 percent of the fish passing Lower Granite have made it to the Sawtooth Valley, a distance of more than 400 river miles.
This year’s return is by far the highest in the history of the program, which was launched in 1991. The total return last year, 833, is next highest and the 2008 return of 650 now ranks third on a list dating back to 1999. And the 2000 return totaled 257, but no other return has numbered more than 26.
The captive broodstock program was started to conserve and rebuild the Redfish Lake sockeye salmon stock in the Sawtooth Valley of central Idaho. The stock had shrunk to the point of near-extinction and was listed in 1991 as endangered under the Endangered Species Act. The first returns from the program were in 1999.
Eyed (fertilized) eggs are planted in egg boxes in lakes and pre-smolts and, primarily, smolts, produced in the program are the source of most of this year’s return. But a growing number of the prespawn adults returning to the basin are the product of adults that either matured in the Pacific Ocean, or were raised to adulthood in hatcheries and released into Redfish to spawn. Of the fish that returned this year, 176 were hatched in the wild.
Kline said that nearly 1,500 adult spawners filled the lake this year, which include about 300 reared to adulthood in hatcheries.
Historically, five Sawtooth Valley lakes – Alturas, Pettit, Redfish, Stanley and Yellowbelly – supported sockeye salmon. Restoration efforts today are focused on Alturas, Pettit, and Redfish lakes.
The young fish that emerge from the gravelly egg nests (redds) next year will spend a little more than a year in the lake before launching on their journey to the Pacific.
Long-term goals include increasing the number of individuals in the population to address NOAA Fisheries Service’s interim abundance guidelines and to provide sport and treaty harvest opportunity, according to a program fact sheet. Draft ESA delisting criteria for Snake River sockeye salmon includes the return of 1,000 adults to Redfish Lake, 500 adults to Pettit Lake, and 500 adults to Alturas Lake for two generations. Interim abundance targets must be met without relying on hatchery production, but on natural origin adults.
“We’re not interested in a one-lake recovery program,” Kline told the Council.
So, there is much work to do. The IDFG earlier this summer completed the purchase of a former southeast Idaho fish hatchery site with the goal of constructing a new hatchery to further boost rebounding numbers of sockeye salmon. The goal is to boost the production of smolts from about 150,000-200,000 per year to as many as 1 million per year. The release of migration-ready smolts has proven to bring the best results, in terms of adult returns, of the program’s release strategies.
The $4.75 million purchase was funded by the Bonneville Power Administration, which pays for fish and wildlife restoration work as mitigation for impacts on fish and wildlife caused by the Federal Columbia River Power System. BPA markets power generated at FCRPS hydro projects in the Columbia-Snake river basin.
The IDFG has launched into the Council’s “three-step” process, which is required of new artificial production proposals. Kline said he expects the state to take the first step – completion of a master plan outlining the proposed hatchery’s preliminary design, goals and funding needs – by October.
“They’re making great progress,” Kline said.
The production of 1 million smolts for release into Redfish Lake Creek and the Salmon River could bring annual returns of 5,000 and more in the future, Kline said.
One of the questions planners have asked is whether Redfish Lake habitat could support an expanded program with more and more adults spawning and more and more juvenile fish rearing in the wild.
Sockeye nursery lake ecology is well researched -- even that of Snake River sockeye salmon, Kline said. Some of that literature focuses on historical sockeye runs to the Stanley basin and the value of marine-derived nutrients to nursery lakes and lake productivity.
Before occupation of the region by settlers of European origins, it is believed that more than 20,000 sockeye salmon returned to the Stanley Basin annually on average.
During that time, sockeye contributed up to 17 percent of the annual nutrient load in Redfish Lake. Then and now, the vast majority of nutrients comes from stream run off, non-channelized run off, and the atmosphere
During the 1990s, researchers estimated that less than 2 percent of the lakes nutrient input was coming from salmon carcasses. A more recent study said that zooplankton species composition had shifted to a less nutritious assemblage of species.
But, Kline said, those assemblages can flip-flop from year to year based in some respects on fish abundance.
“It’s not static,” Kline said. The most recent monitoring – earlier this year – shows “a renewed presence of the most desireable zooplankon that sockeye prefer,” Kline said.
“We’re encouraged” that the lake, with some ups and downs, can still handle a much larger sockeye population, Kline said.
The IDFG is taking a “step-wise approach” to rebuilding the sockeye population, Kline said.
First comes the expanded smolt production. Then, with increased returns there will be increased use of anadromous adults in hatchery spawning designs (replacing captive adults).
There will also be increased use of anadromous adults in the habitat, Redfish Lake initially and then expansion to a multiple lake reintroduction program after a period of demonstrated success in Redfish.
The strategy is aimed at taking advantage of local adaption and associated fitness improvements of fish that begin and end their life in the wild.