Federal researchers report a total 60 percent survival rate in 2006 for juvenile Snake River spring chinook salmon as they migrated past eight dams to the sea. Officials said that is the highest survival rate for the threatened species since federal research began in 1993.
“This record high survival is good news for this species,” Northwest Power and Conservation Council Chairman Tom Karier said. “High survival of juvenile salmon is an important objective of regional recovery efforts.”
NOAA Fisheries conducted the research, which also found the survival rate for juvenile Snake River steelhead in 2006 — 37 percent — was lower than the chinook rate, but still good when compared to recent years. The researchers reported their findings to a July council meeting in Missoula, Mont.
The research focuses on in-river migrants — rather than fish transported in barges — as they travel from hatcheries where they are incubated, past dams, and to the Columbia River estuary, where they remain for up to a year before entering the ocean. The research involved only fish implanted with passive integrated transponder (PIT) tags, whose movements are recorded by PIT tag detectors.
Mortality causes include dam passage, predation, natural selection, and, importantly, water temperature. The scientists said prolonged exposure to warm water is lethal to salmon and steelhead.
The research found that survival of juvenile salmon and steelhead from Idaho hatcheries to 810-MW Lower Granite Dam, the first dam they encounter on their journey to the ocean, varies with the distance traveled, with fish traveling the farthest experiencing the highest mortality. Lower Granite is the first of eight dams the fish pass on their way to the ocean.
More dams, but higher survival than the 1960s
Research also found that fish are surviving the journey better today than in the 1960s when there were only four dams in place.
The research also indicated:
o There appears to be a weak but positive correlation between higher flows and higher survival;
o Water temperature seem to have greater effect on survival than flow; survival appears to decrease as temperatures increase;
o Guiding fish over spillways, particularly via removable spill-way weirs like those now at Lower Granite and 603-MW Ice Harbor dams, and planned for other dams, could boost survival further;
o Ocean conditions appear to override the benefits of improved fish passage, as poor ocean feeding conditions in the mid-1990s correlated to poor smolt-to-adult return rates for Snake River spring chinook and steelhead;
o More information is needed to improve survival estimates for juvenile Snake River fall chinook, particularly for those fish that spend their first year in Snake River reservoirs as opposed to migrating to the ocean immediately after birth.
Returning salmon, steelhead survival averages 98 percent
Researchers also found the survival of adult salmon and steelhead at, and between, dams on the Columbia and Snake rivers is averaging 98 percent and better in recent years. A NOAA Fisheries scientist made that observation to another meeting of the Northwest Power and Conservation Council.
“That’s real high survival; most people would agree those are good numbers to have,” Ritchie Graves, acting branch chief of NOAA Fisheries’ Hydropower Division in Portland, said.
Karier, the council chairman, called results encouraging.
“At least the adult salmon do not appear to have difficulty with the dams,” Karier said. “This is good news if we are only losing 1 or 2 percent of the fish migrating upstream.”
Council Member Judi Danielson said the results bode well for salmon and steelhead returning to Idaho.
“We hear so much about the impact of the dams, but here is data that shows we have done so much to improve passage survival through the hydro system,” Danielson said. “Now it is time to sharpen our focus on improving fish survival in other areas, particularly har-vest, which has been 9 percent or more on these fish between dams.”
Graves presented results for chinook and steelhead survival:
o Between 1,092.9-MW Bonneville (past 1,807-MW The Dalles and 2,160-MW John Day) and 980-MW McNary dams;
o Between McNary (past 907-MW Priest Rapids, 1,038-MW Wanapum, 623.2-MW Rock Island, and 1,287-MW Rocky Reach) and Douglas County Public Utility District’s 840-MW Wells Dam on the Columbia; and
o Between McNary (past 603-MW Ice Harbor and 810-MW Little Goose) and Lower Granite Dam on the Snake.
Wild and hatchery-reared spring chinook that had been released as juveniles above Lower Granite Dam experienced about 99 percent survival between Bonneville and McNary dams when they returned as adults, and 99-100 percent survival between McNary and Lower Granite dams, he said. Survival of Snake River summer and fall chinook between McNary and Lower Granite dams, and for upper Columbia steelhead between McNary and Wells dams, averaged 97-98 percent.
Nearly 124,000 spring chinook salmon passed Bonneville Dam on their way up river by the official close of the season June 14, after one of the latest starts on record, NOAA Fisheries and other federal agencies reported. That is better than last year’s chinook count of 95,000 fish and is higher than projections.
NOAA Fisheries Regional Director Bob Lohn said the spring run made a respectable showing, but salmon runs are variable. He said improved in-river conditions do not always translate into larger runs because the ocean plays an even greater role in survival.
Increased spills on Columbia, Snake cost $60 million
Bonneville Power Administration reports this year’s court-ordered spills at Columbia and Snake dams are reducing generation amounting to a revenue loss of $60 million.
The spring and summer spills, ordered by U.S. District Judge James Redden to help juvenile salmon and steelhead migrate, are to continue through Aug. 31 at all four lower Snake River dams and the four mainstem Columbia River dams.
BPA also reported it spent a total of $2.7 billion from 1978 through 2005 to buy electricity to meet its load requirements in response to required river operations that reduced hydropower generation at Columbia and Snake river dams.