With more and more adult fish landing in central Idaho’s Redfish Lake to spawn, researchers involved in the long-running Snake River sockeye salmon revival program are beginning to see, as expected, a stronger contribution to the annual juvenile outmigration from naturally produced smolts.
The Snake River Sockeye Salmon Captive Broodstock Program was started in 1991 as a means of saving a population that had dwindled to none. It was launched in May, before the National Marine Fisheries Service listed Snake River sockeye salmon as endangered under the Endangered Species Act of 1973, on Nov. 20, 1991.
Program coordinators include the Idaho Department of Fish and Game, NOAA Fisheries, the Oregon Department of Fish and Wildlife, the University of Idaho, the Shoshone-Bannock Tribes and the Bonneville Power Administration.
In 1990 there were no wild sockeye counted at the lower Snake River’s Lower Granite Dam. The dam is the eighth and final hydro project the sockeye spawners pass on their 900-mile trip up the Columbia, Snake and Salmon rivers to Idaho’s Sawtooth Valley.
Other annual counts between 1984 and 1998 ranged from two fish in 1998 to 47 fish in 1984. Between 1991 and 1998 a total of only 16 wild sockeye returned to Idaho.
But by 1999 the captive broodstock program had begun to see the returns of adult fish that had been released from the hatchery. The returns were low early on with the exception being 2000 when 299 passed Lower Granite and 2004 when 113 headed up that 400-mile home stretch to the Sawtooth Valley.
But numbers have improved in recent years with a count of 909 in 2008, 1,219 in 2009 and 2,201 in 2010.
A total of 650 anadromous adults actually made it back to the Stanley basin in 2008. The total was 833 anadromous adults in 2009 and 1,355 in 2010. Returning adults are trapped at two locations -- Redfish Lake Creek and the Sawtooth Hatchery
This year a total of 1,413 sockeye had been counted at Lower Granite through Thursday, which is already the second highest number of sockeye to pass that way since the early 1950s. Counts there have begun to dwindle, falling from a peak daily count of 110 on July 14 to 18 on Thursday.
So far (through Wednesday), only one of those fish have made it those final 400 miles up to the Stanley basin. Most of the fish that do finish their round trip will be released into Redfish Lake in September and will spawn in October. Most of their progeny will migrate to the ocean in May 2013, and survivors would mostly likely return as adults in August 2015.
The program releases eggs and fish back to the habitat in a variety of ways. Eyed-eggs are planted in egg boxes and placed in lakes in the fall, presmolts are released directly to lakes in the fall, smolts are released to outlet streams in the spring, and prespawn adults are released to lakes in the fall. A monitoring and evaluation effort is in place to document the success of the different reintroduction strategies. The three lakes targeted in the recovery effort are Redfish, Pettit and Alturas.
The program has through time learned that the best artificial production strategy for rekindling natural production is the rearing and release of smolts, age 1-plus-year-old fish that are ready to begin their journey to the Pacific Ocean. The program has thus built to a capacity that has allowed as many as 200,000 smolts to be produced in recent years.
A planned new hatchery could boost that production to as many as 1 million smolts.
This year's adult returns will result primarily from smolts that migrated to the ocean in 2009. In that year, about 210,336 natural origin and hatchery-produced smolts left the Sawtooth Valley in route to the ocean, according to the IDFG.
Meanwhile, returning sockeye and fish raised to adulthood at Eagle Hatchery near Boise and at a NOAA Fisheries facility in Washington are being released into Redfish Lake in greater and greater numbers. In 2008 398 hatchery-reared and 571 anadromous adults were turned loose to spawn in Redfish. Fish that return to either Sawtooth Hatchery near Stanley and Redfish Lake Creek are, for the most part trapped and held at Eagle Hatchery until spawning time in September. There they are sampled for genetics, disease and other reasons.
Researchers estimate that about 14,000 naturally born smolts from Redfish Lake – most of which were the product of the 2008 adult releases -- joined the 2010 outmigration.
In 2009, 682 hatchery reared and 667 anadromous adult fish, 1,349 in all, where loosed in Redfish. This year, very preliminary estimates are that about 6,800 smolts produced by those 2009 spawners joined the outmigration.
“This year we definitely expected more fish,” IDFG researcher Mike Peterson said. All is not necessarily lost however. Sockeye are considered to be particularly savvy, choosing when conditions are right to swim toward the ocean, if at all.
“Zooplankton levels in Redfish Lake are very high,” which means the young fish have an ample food supply, Peterson said. “These fish may have chosen to stay for another year in the lake and grow some more.” Sockeye salmon feed extensively on zooplankton during both freshwater and saltwater life stages.
“I wouldn’t be surprised to see a lot more 2-year-olds leaving the lake next year,” Peterson said. Typically about 2 percent of the outmigration from Redfish have been 2-plus-year-olds but that percentage has been as high as 15 percent.
Last year’s record anadromous sockeye return to the Stanley basin allowed the release of 1,582 adults into Redfish Lake. That total included 372 captive adults (76 females) while 1,210 were anadromous returns (489 were female).
The hatchery and naturally produced smolts heading toward the ocean this year appear to have fared well, coasting downstream in flows that have been higher and cooler than normal.
“We’re seeing really good survival,” Peterson said. Data retrieved from young fish equipped with PIT tags indicates that survival down to Lower Granite has been 72 to 75 percent. Typically it takes the young fish about 9-12 days to reach that first dam in the system.