Extraordinary returns of naturally spawning Snake River steelhead five years ago followed by steady declines and a dismal run this year triggered an "early warning indicator" that is prompting federal agencies to take formal steps to determine if "rapid response actions" should be taken to avoid further declines.

In an Oct. 23 letter to BPA, the U.S. Army Corps of Engineers and the Bureau of Reclamation, NOAA Fisheries wrote that it intends to implement adaptive management measures first incorporated in its supplemental Federal Columbia River Power System BiOp in 2010, and included in the 2014 and 2019 BiOps.

Early warning indicators ensure prompt analysis and action, if necessary, when ESA-listed fish numbers in the Columbia Basin drop to a certain point, or decline rapidly.

In 2014-2015, about 45,789 naturally spawning steelhead passed Lower Granite Dam on the Snake River—the highest since the mid-1980s, according to the letter. Five years later, only 8,182 wild steelhead passed the dam, the lowest returns since 1994-1995 and 1995-1996. The four-year average abundance is now 17,705 steelhead.

"The high return in [2014-2015], coupled with the poor ocean conditions experienced beginning with the 2015 smolt out-migrations, appear to be the primary cause," the letter states. It says that both upper Columbia and mid-Columbia river steelhead have seen similar declines in numbers and abundance trends, but not enough to trigger the early warning indicator.

NOAA Fisheries spokesman Michael Milstein said the BiOp's early warning system has not been triggered before. He said NOAA scientists liken the warning to a check engine light in a vehicle.

"It's a general warning" that doesn't necessarily signal a serious problem, he said, but, "it does say we need to take notice and look more carefully at what's likely to happen in the next year or so."

NOAA Fisheries and other agencies will try to determine in the next four months if the poor returns will continue, resulting in a "significant decline trigger" over the next two years, which would lead to rapid response actions.

Several actions identified in the adaptive management plan have already been implemented in recent years, the letter says. They include more spill through the 2019 flexible spill operation, an earlier barge transport start date beginning in 2018, and a curtailment of recreational steelhead fishing this year.

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.