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NW Power/Conservation Council Hears ‘Lessons Learned’ Report On High Mortality For 2015 Sockeye Run
Posted on Friday, April 15, 2016 (PST)

Quicker decisions by river managers could have changed the outcome of the adult sockeye salmon runs in the Snake River and in the upper Columbia River, according to a 2015 sockeye salmon passage report released as a draft this week.

 

In 2015, low flow conditions, coupled with extremely high air temperatures and warm water in the major tributaries in the lower Snake and Columbia rivers from mid-June to mid-July, resulted in the highest mainstem temperatures recorded in the Columbia River.

 

“There was a lot of in-season discussion about survival and getting fish past the Snake River projects,” said Ritchie Graves, chief of the Columbia Hydropower Branch at NOAA Fisheries. “But, we probably talked too long. We needed to act more decisively.”

 

Graves and Idaho Department of Fish & Game’s Russ Keifer presented a draft of the report to the Northwest Power and Conservation Council at the Council’s meeting Wednesday.  The U.S. Army Corps of Engineers also participated in compiling the “lessons learned” report. The report has yet to be published.

 

As it was, few Snake River sockeye made it to Lower Granite Dam and even fewer found their way to spawning grounds.

 

In fact, 99 percent of Snake River sockeye that were counted crossing Bonneville Dam died before they reached the upper Salmon River’s Sawtooth Valley where the salmon, listed as endangered under the federal Endangered Species Act, spawn. Just 56 adult sockeye salmon made it on their own to the Sawtooth Valley and another 51 were transported from a trap at Lower Granite Dam to the Eagle Hatchery in Idaho.

 

And only 3 percent to 4.5 percent of the fish heading up the Columbia River and into the Okanagan River ever made it to the spawning grounds. Some 10 percent to 15 percent made it to the Wenatchee River to spawn, the passage report said.

 

“The glass is half full,” Graves said when asked what the long-term impact on sockeye salmon in the basin would be. “It was a really big sockeye run, so it likely will not have a long-term effect on the population. Sockeye are pretty well equipped for a one-time event like last year. But if it happens three times out of five, that could be a different story.”

 

He added that the draft lessons learned study sums it up as “this could happen more often in the future.”

 

“If rare, events are unlikely to have a large or lasting impact to the viability of sockeye salmon populations because their complex life histories provide resiliency against catastrophic events,” according to the Council’s memorandum for the presentation (http://www.nwcouncil.org/media/7150172/5.pdf).

 

“However, should similar events occur frequently, sockeye salmon populations in the Columbia River basin would be substantially impacted.”

 

“The fish that did make it went through some very brutal selection,” Keifer said, summing up the summer sockeye return in both the Columbia River and Snake River.

 

Yet, the answer to better survival wasn’t so simple as to just make faster decisions.

 

Salmon managers, such as those who make up the Technical Management Team and who make weekly decisions about the operation of the Columbia/Snake federal hydroelectric system as they relate to listed fish, also received information later than was needed and some of the information – temperature and adult fish ladder counts – could have been improved, the report said.

 

In addition, the salmon faced river conditions that were almost unprecedented with low flows and high temperatures in the Snake and Columbia rivers occurring far earlier than normally encountered.

 

The poor performance by the fish was not due to a lack of numbers: 2015 had record-breaking runs of sockeye, with 510,706 sockeye heading past Bonneville Dam. Some 476,000 of those fish migrated into the upper Columbia spawning grounds (the 10-year average is 241,351), all unlisted.

 

Over 4,000 sockeye, a recent high, were on their way to the Sawtooth Valley, according to Graves.

 

Much of  the problem was the timing, Graves said, citing a Fraser River study showing that sockeye salmon like to migrate somewhere in time between higher spring flows and higher summer temperatures. High flows burn fish energy as do high temperatures, Graves said.

 

At 68 degrees Fahrenheit sockeye salmon begin to die and most of the fish passed Bonneville after the water temperature had hit 23 degrees C (73 degrees F).

 

“That window closed pretty fast this last year,” Graves said. The sockeye salmon missed their migration timing window as record warm water temperatures met them earlier than expected.

 

“When it’s really hot you really need to know where you’re going when you’re a sockeye salmon,” Graves said.

 

The low runoff volume of 58,407,000 acre feet and 67 percent of average at The Dalles Dam, April through August, ranked 54 lowest out of 56 years. A similarly dismal runoff volume at Lower Granite Dam on the Snake River ranked 53 out of the past 56 years, with a runoff of 11,466 kaf, 54 percent of average.

 

In June, air temperatures were consistently 6.4 to 7.4 degrees F higher than average at all of the mainstem Columbia River dams. The river temperature on the Salmon River hit 78 degrees in late June and early July, and the Okanogan River, the most northerly point in the system, according to Graves, peaked at 82 degrees July 1.

 

Survival rates from Bonneville Dam to McNary Dam were estimated to be in the 60 percent range for the upper Columbia River sockeye, but only 26 percent for Snake River adult sockeye that had migrated in-river as juveniles and just 5 percent for adult sockeye that had been transported when migrating downstream.

 

Surprisingly, Graves said, water from Grand Coulee Dam, June through July, actually kept the Columbia River cooler 1 degree C (1.8 degrees F) compared to the temperature of the water flowing into the dam. That dynamic changed later in the summer, Graves said, but the sockeye run had pretty much run their course by then.

 

“There is some indication that summer chinook were impacted, but for steelhead and fall chinook we’re not sure,” he said.

 

The Hells Canyon Dam on the Snake River also helped to keep the Snake River cooler.

 

The Snake River is a desert river, Graves said, and before the dams were in place on the river and before Dworshak Dam was used to modify temperatures downstream, the temperature at the mouth of the river, below a point where Ice Harbor Dam is now, peaked in mid-July to early-August at 23 to 24 degrees C (73.4 to 75.2 degrees F).

 

Lessons learned from the 2015 sockeye migration, according to the draft report, are:

 

--Air and river temperatures in June and July were much higher than historical data.

 

--The river system’s large reservoirs – Grand Coulee, Hells Canyon Complex and Dworshak Dam helped to keep the rivers cooler, but temperatures were still high.

 

--Adult ladder counts may be biased during high temperature periods. There was increased fallback and some adult fish fell back through as many as two dams.

 

--Fish ladder temperature and reporting could be improved. The Corps is good at collecting data, Graves said, but it would be useful to have the data more readily available for faster decision-making.

 

--Faster decision-making could have benefitted adult sockeye in 2015.

 

--Snake River sockeye that migrate later than upper Columbia River sockeye are exposed to higher temperatures between Bonneville and McNary dams and will die at higher rates because of that.

 

--Adult sockeye transported as juveniles survived at a lower rate than juveniles migrating in-river.

 

--The highest losses were in the upper Columbia River reaches and from Lower Monumental to Little Goose dams on the Snake River.

 

--Adult losses in the Salmon and Okanogan rivers were also high.

 

--Adult sockeye transportation from Lower Granite Dam to the Eagle Hatchery appeared to be an effective “hedge” strategy.

 

Some of what could be done is already in process, such as getting a better handle on data, improving future decision-making, reducing as much as possible the negative impacts of high temperature on sockeye salmon and thinking more about the successful trap and haul operations at Lower Granite Dam.

 

In addition, the Corps has just completed a pumping facility at Lower Granite Dam that mixes cool water from the reservoir’s bottom. That will help cool the dam’s fish ladders that last year saw temperature differentials (top to bottom) of greater than 1 degree C (1.8 degrees F), a temperature differential that discourages salmon from migrating up through the ladder.

 

Items that need work are a contingency plan with “triggers” that offer managers a next step, improving PIT-tag detection systems and improving transport vs in-river assessments, developing and implementing alternative solutions and, finally, adaptively managing the system to maintain cool temperatures when the river again sees the high temperatures of 2015.

 

Also see:

 

--CBB, April 1, 2016, “Corps Report On 2015 Columbia/Snake Warm Water, Fish Die-Off Will Discuss Actions To Avoid Repeat,” http://www.cbbulletin.com/436358.aspx

 

-- CBB, December 4, 2015, “Post-Mortem 2015 Snake River Sockeye Run; 90 Percent Of Fish Dead Before Reaching Ice Harbor Dam,” http://www.cbbulletin.com/435642.aspx

 

-- CBB, November 6, 2015, “Report Analyzes Impacts, Causes Of This Year’s Warm Fish-Killing Water In Columbia/Snake,” http://www.cbbulletin.com/435505.aspx

 

-- CBB, September 11, 2015, “Snake River Sockeye: Lowest Return Since 2007, Captive Broodstock Program Increases Spawners,” http://www.cbbulletin.com/434944.aspx

 

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