Study Tracks Sockeye 'Conversion' from Lower Granite
High water temperatures and fallback stress may be the biggest enemies, along with harvest, of endangered Snake River sockeye salmon species trying to make their way up roughly 900 miles of the Columbia, Snake and Salmon rivers to central Idaho's Sawtooth Valley, according to preliminary results presented Tuesday at the U.S. Army Corps of Engineers annual Anadromous Fish Evaluation Program research review.
The latest of the summer migrants are most likely negotiating water temperatures that are unhealthy for the cold water creatures.
"None of the late fish make it," NOAA Fisheries' Liz Crozier said of sockeye that arrive when summertime water temperatures in the Snake have risen to their annual peak.
"None of the fish that experience those high temperatures made it" from the lower Snake's Lower Granite Dam up the next 400 river miles to their Sawtooth spawning grounds.
Likewise sockeye that climb fish ladders and then get swept back downstream, such as through spill gates, have a much lower probability of completing their spawning journey, Crozier said.
"Some of these fish are falling back as many as nine times," Crozier said of sockeye equipped with passive integrated transponder tags that allow them to be detected and identified at dams up and down the system.
Forcing repeated ascents likely depletes the fishes' energy stores.
The annual percentage of the tagged fish that fell back at Lower Granite has been as high as 38 percent "and it's even higher in 2013," Crozier said. The fallbacks can also serve to confound dam counts taken by human observers.
The conversion rate appears to be quite low because the fish appear in the count windows numerous times.
Only 270 were trapped and counted in the Sawtooth Valley (most were later released and allowed to proceed to Redfish Lake to spawn). A total of 757 sockeye were counted at Lower Granite.
In the past that conversion rate has often been up to 70 percent. Higher than normal water temperatures in the river and in the dam's fish ladder are believed to have delayed fish passage there this year.
Lower Granite is the eighth and final dam the fish must pass on their way to Idaho high country. The Snake River sockeye returning to Redfish Lake travel farther from the Pacific Ocean, almost 900 miles, to a higher elevation, more than 6,500 feet, and are the southernmost population within its recognized range.
But because of a variety of factors the stock's numbers dwindled, literally to zero in some years. Redfish Lake sockeye salmon were listed as endangered under the Endangered Species Act in November 1991 - the first Idaho salmon species to be listed.
Between 1991 and 1998 only 16 wild sockeye returned to Idaho. They were brought into the Idaho Department of Fish and Game's Eagle Hatchery to serve as broodstock with the original intent of assuring that genetic stock was preserved.
Between 1999 and 2007, 355 adult fish returned to the Sawtooth Valley, all the product of the broodstock program. The broodstock program has helped lift annual returns, largely via the release of hatchery reared smolts.
A new hatchery that went online late this fall is expected to raise production to as many as 1 million smolts per year, which would be nearly five times the current level. The goal is to create a self-sustaining natural population.
The increase in smolt production is called for in NOAA Fisheries' 2008 Federal Columbia River Power System biological opinion, which prescribes measures intended to boost listed salmon stocks' survival. The idea is to send out more sockeye smolts so that higher numbers of the species survive to adulthood and return to the Salmon River basin to spawn in the wild.
The study led by Crozier is intended to identify causes of adult sockeye mortality during their trip upstream and use, potentially, those factors to determine whether conditions might require that the fish be trapped, at Lower Granite, and transported aboard tanker trucks upstream to the Sawtooth Valley.
The research, through analysis of harvest and environmental data such as water temperatures and flow volumes, is trying to identify "what kind of cues would be appropriate" to trigger a transport operation, Crozier said.
Because recent conversion rates from the FCRPS to the spawning grounds have not met recovery goals outlined in the federal salmon recovery plan (the BiOP), recent efforts involve identifying the causes of mortality within and upstream of FCRPS, and examining transportation from Lower Granite Dam to the spawning grounds as a potential management tool, according to an abstract for the research project.
The statistical model that has been developed by the researchers for the project will be used -to estimate this year's conversion rate, which could help validate use of that model for making future transportation decisions in years when conditions might not be conducive to high spawner survival.
The conversion rate is the percentage of fish that survive from one detection point to another.
The objectives of this study were to use available PIT-tagged adult sockeye salmon from 2008 to 2013 to 1) estimate detection efficiency for each available location between Bonneville and Lower Granite dams, 2) estimate conversion rates for each available reach between Bonneville and Lower Granite dams, 3) estimate conversion rates from Lower Granite Dam to the Sawtooth Valley, 4) describe migration characteristics, including travel times, migration timing and fallback at all available locations within and upstream of the FCRPS, 5) correlate migration fate within and upstream of the FCRPS with migration characteristics, origin, genetic history and temporal and environmental factors, and 6) identify trigger mechanisms for initiating transport of adult sockeye salmon from Lower Granite Dam to the Sawtooth Valley, if possible from available data.
"We analyzed covariates of migration fate over various stretches, including from Bonneville-Lower Granite (BO-LG, n=929 fish detected at BO from 2000-2013), and Lower Granite to Sawtooth Valley (LG-SW, n=556 fish detected at LG, 1996-2013). We will test proposed triggers of migration fate based on data prior to 2012 against observed fates in 2013 when the migration is complete," the abstract says.
Also charted were the reaches from McNary to Ice Harbor to Lower Granite.
Climate Change Impacts Suggest Snake River Fish Passage Facilities Need 'Thermal/Hydraulic' Features by Staff, Columbia Basin Bulletin, 1/10/14
Keeping Fish Moving During Hot Times at Lower Granite Fish Ladder by Staff, Columbia Basin Bulletin, 12/20/13
Columbia System Gets Hotter and Deadly for Salmon and Steelhead by Rocky Barker, Idaho Statesman, 7/30/13
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