Snake River Night

Snake River.

Forty-two percent of Snake River basin spring-summer Chinook populations have reached quasi-extinction thresholds, according to a study by Nez Perce Tribe scientists, who say if adult returns continue to decline at 19 percent per year, 77 percent of the populations will reach the threshold by 2025.

The situation isn't quite as bad for Snake River steelhead, but is still concerning, with 19 percent of the populations already at quasi-extinction, and 44 percent projected to get there by 2025 if adult returns continue to decline at 18 percent each year.

Tribal officials presented their findings to the Northwest Power and Conservation Council on May 5, and issued a "call to action" that includes their support for breaching the four lower Snake River dams, such as Rep. Mike Simpson (R-Idaho) is proposing.

"Something needs to be done in a big way, and it needs to be done now," Dave Johnson, manager of the Nez Perce Tribe Department of Fisheries Resources Management told the Council. "The tribe thinks that a big initiative like something that Congressman Simpson is proposing kind of hits the mark," he said.

Johnson said the region should also be considering a captive broodstock program to preserve the genetics of Snake River populations, perhaps raising them at a hatchery below Bonneville Dam until the problems can be resolved. "We have to have these fish. They cannot go away. These are what the tribes depend on. We will do everything that's possible to keep them around, at least to maintain the genetics," he said.

The analysis of 31 ESA-listed runs of Snake River spring-summer Chinook and 25 ESA-listed steelhead runs was initiated when biologists noticed the Tucannon River Chinook returns had plummeted despite extensive habitat work and a native hatchery program, Johnson said. He noted that biologists wondered whether the Tucannon is different from other tributaries in the Snake River basin.

Tribal biologists are also reviewing NOAA Fisheries' draft viability assessment and helping with the technical review, he said.

The tribe used numbers from NOAA's assessment, added another year's worth of data and concluded that multiple populations had reached the quasi-extinction threshold, which is 50 or fewer natural-origin spawners for four consecutive years. It's just one step above becoming functionally extinct and reminiscent of their numbers when Snake River Chinook and steelhead were listed in the 1990s, Johnson said.

"We think this is terrible news. It is a call for alarm," he said, adding, "We need to do something big. We need to do something more than we have been doing."

NOAA Fisheries spokesman Michael Milstein said that the agency is in the middle of a five-year status review for ESA-listed stocks, and those results will help determine what else can be done now and in the long-term for the Snake River stocks.

Milstein also noted that a lot of new efforts are in place with the 2020 BiOp, including more spill to improve juvenile salmon survival.

"The status quo has been left behind," he told Clearing Up. "We're doing things that have not been done at this scale before. Which is not to say there's some magic answer, or we've figured it out, but a lot of people are working really hard to try to improve the picture."

Milstein said any additional measures need to be informed by the status review, which is expected to be completed by the end of the year.

The Council memo on the presentation noted that the viability assessment is based on the prior five-year period of available data, and does not forecast future viability.

The tribe looked at natural-origin spawner abundance for the past 10 years—from 2011 through 2020—for each of the Snake River's spring-summer Chinook populations and found all of them have been declining at about 19 percent per year. They did the same for Snake River steelhead and found declines of 18 percent per year. The analysis also found that the larger "B-run" populations are declining at a faster rate than the smaller "A-run" steelhead.

Johnson was joined by the Nez Perce Tribe Fisheries' Director of Biological Services Jay Hesse, and Research Scientist Ryan Kinzer, who presented their analysis to the Council.

Kinzer noted that the low numbers in the 1990s led to listing under the Endangered Species Act, which in turn led to a number of actions, including construction of hatcheries and cryopreservation.

"Then we really got lucky, and the ocean turned around," he said. Abundance in the early 2000s can be largely attributed to the ocean becoming better for survival, he said. But their numbers have been declining for the past 10 years.

Hesse said that the realization that ocean conditions have a huge impact on returns is one that scientists are beginning to better understand. But freshwater survival can play a critical role in the percentages of smolt-to-adult return rates, which help determine the survivability of a run.

According to the presentation, the desired level for healthy and harvestable returns for all of the Snake River spring-summer Chinook stocks added together is to have 179,000 adults returning to Lower Granite Dam, while 29,250 fish are needed above the dam for delisting. A critical or quasi-extinction level for all of the runs is 1,850 Chinook crossing Lower Granite.

This year, 8,150 natural-origin spring-summer Chinook are projected to cross Lower Granite. That's about half of 10-year average of 14,259 Chinook.

Snake River steelhead are at healthy and harvestable levels when about 100,000 cross Lower Granite Dam, and delisting would require passage of 20,000 fish at the dam. The quasi-extinction level is 1,200 fish at the dam.

The 2021-2022 forecast for natural-origin steelhead returns is 14,450 adults, and the 10-year average is 22,713 fish.

Johnson said the Nez Perce Tribe has done a lot of restoration work over the last 30 years, and raises a lot of fish in hatcheries to try to sustain the runs.

"They do keep some numbers on the board, which is very important," he said. "What we are very much concerned with is working to where we can float all boats. We have to be able to help all of the various populations," he said.

Johnson suggested that in addition to breaching the four lower Snake River dams, a larger focus should be spent on issues in the main stem Snake and Columbia rivers, including predator abatement, hydro system improvements and addressing the presence of nonnative fish. "Smallmouth bass, walleye—they're not supposed to be here. This is salmon habitat," he said.

Council member Jeff Allen noted that overall numbers of Chinook and steelhead passing Lower Granite Dam are higher than in the 1990s, and asked how so many of the major populations can still be in trouble.

Johnson said that while the numbers include the Clearwater River and other populations that were rebuilt, other runs have not responded and for the past 10 years all of the stocks are declining at similar rates.

Hesse said that when Snake River spring-summer Chinook were listed, the rate of decline was lower than now, at about 9 percent for the period from 1983 to 1992.

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K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.