This is a story from one lifetime ago in the highest salmon grounds on earth, Idaho’s upper Salmon River.
It bears on a judgment many Northwest residents and elected leaders are now making: whether restoring free-flowing conditions in the lower Snake River by removing its dams can restore a new version of salmon abundance in Idaho and northeast Oregon.
Salmon and steelhead had one opportunity to re-populate the upper Salmon River after being blocked from it for years by a dam in the 1930s and 1940s.
In 1910, Sunbeam Dam was built on the Salmon River. The dam generated electricity for a mine up the Yankee Fork for only one year because the mine company bankrupted and closed. For 23 more years, the useless dam blocked passage of Chinook salmon, sockeye salmon and steelhead trout to the entire upper Salmon above the Yankee Fork. For a quarter-century, the people, fish, wildlife, forests and streams of what is now the Sawtooth National Recreation Area were without the food and fount of life that is salmon.
In 1934 the Idaho Fish and Game Department blasted a hole where canyon wall and dam joined. It took a few more years, with more blasting and the river’s high water muscle each spring, to form a channel salmon could reliably navigate.
Bill Platts does not remember seeing the dam intact. But as a boy in the late 1930s, and through the ‘40s, he came up each summer from Magic Valley into the upper Salmon to fish. He remembers few Chinook there in 1939. He might camp near Redfish Lake, but to catch salmon he had to go down to the Yankee Fork, or over into the Middle Fork Salmon’s headwaters. Around 1941, he began seeing salmon more regularly in the Sawtooth Valley and Stanley Basin. By 1946-48, he remembers streams being full of Chinook — in Basin Creek, Valley Creek, lower Pettit Lake Creek, Alturas Lake Creek, Smiley Creek, Frenchman Creek and sections of the main river.
From no or, at best, a handful of Chinook in 1934 to good runs in 1946-48: how did salmon come back so fast? Platts’ educated surmise (he’s an aquatic scientist) has two main factors.
First, a good source of Chinook was present each summer in the 200 yards below the dam: salmon destined for the Yankee Fork. Salmon were plentiful then in the Yankee Fork, especially in its West Fork, and were much fished. In addition to normal straying by fish from this population, polluted water from decades of mining likely led many Yankee Fork-bound salmon to stay in the main river’s cleaner current for the short distance to where the dam barred their way.
In River Runts, Ted Merrill recounts holding his mother’s hand in 1931 while looking upstream, from across the road, at the still intact dam. They watched salmon after salmon launch into the torrent shooting from the dam’s exit tunnel, then be thrown back into the foaming plunge pool just below it. That pool was a prime, if challenging, fishing spot. Salmon could not get through the dam, but each year it seems many tried. If some hundreds of salmon congregated right below the dam each summer when the dam was whole, many would have quickly followed the restored current up past the dam once it was opened.
Second, smolt-to-adult return, or SARs, ratios for Snake River salmon were high in those years. While direct SAR measurement only began in the 1960s, in 2020 Petrosky and co-authors used indirect evidence to find that “historical levels of life cycle productivity [for Snake River Chinook salmon] are associated with SARs approaching 6%.” That is, of every 100 young fish going seaward, six adults returned two-to-four years later. Today, upper Salmon Chinook SARs average below 1%, an extinction rate. But in the late 1930s and ’40s only one dam interrupted their downstream migration, not today’s eight.
From a starting point of 100 Chinook adults, a sustained 6% SAR can generate up to 900 adults in two generations (roughly 10 years) and 2,700 in three, if the spawning and rearing habitat allows. The Upper Salmon’s Chinook habitat was extensive, excellent, and empty, ready for salmon to burst back in. Platts also remembers that sockeye salmon came back even faster to Sawtooth lakes than Chinook did to the streams.
Sunbeam Dam and the lower Snake dams differ in many ways. Sunbeam blocked salmon; the lower Snake dams choke them. Sunbeam blocked only the upper Salmon; the lower Snake dams choke down on every Snake River salmon and steelhead, twice. Sunbeam’s dam made a lake 2 to 4 miles long; the lower Snake’s four dams make a continuous reservoir 140 miles long. Sunbeam had no purpose at all after one year; the lower Snake dams have hydropower and navigation purposes. $750 of dynamite began the Salmon River’s re-opening through Sunbeam Dam; opening the lower Snake dams will be a restoration project of world scale. Many relevant Idaho and Northwest conditions are different now than a lifetime ago.
But there are basic constants: the genius in salmon to self-restore, if given the chance, and a few hundred miles of great upper Salmon spawning and rearing habitat, nearly empty of salmon but ready to support a comeback. A third needed constant — good enough health in the big downstream rivers to the sea — is the open question. Will the durable productivity that salmon sustained in the 1940s, when migratory conditions to and from the ocean were healthier, be significantly restored if the lower Snake dams go?
A 25-year federal/state/tribal salmon science collaboration, the comparative survival studies, say yes. Their 2019 report estimates that re-opening the lower Snake, coupled with effective salmon spill at the four Columbia dams that will remain, will increase Chinook SARs in the Salmon River to a mean of 5.1 percent. A 5 percent SAR will take a bit longer than 6 percent to re-build salmon, but if sustained, it will do the job fine. The conclusion of the comparative survival studies is based on deep probes into vast stores of data. A large majority of individual salmon scientists have reached the same conclusion from both data and their experience.
The Sunbeam story also carries a less positive lesson or two. For example, how little value salmon have often had for some Idaho people and leaders. But from a fish and river view, the main lesson is that when the door to restore is opened, salmon will be ready and restoration can be quick. We can have faith that large and generous action on the salmon’s behalf – the return of 320 miles of free flowing migratory habitat between Idaho and ocean – will produce recovery to some level of abundance.
Writer’s note: I thank Bill Platts, Tom Stuart, Ed Cannady, Rocky Barker and Julia Page for particular help with this piece.
Additional notes and references:
 Fish ladders for returning adult salmon were attempted twice. Both were ineffectual, though a few fish likely made it through. There are also reports of individual people hand-carrying a few fish above the dam.
 Rocky Barker, in Saving All the Parts, records an earlier attempt to blow the dam in 1931, by unidentified fishermen angry at the blockage. Since restoring passage took a series of events, not one alone, I credit both Idaho fishers and their fish agency.
 Salmon have high fidelity to their stream place of birth, but a small, regular percentage of 5 to 10 percent stray elsewhere. It’s a kind of scout, and hedge against local catastrophe for the population the strays are part of.
 River Runts, Ted and Bill Merrill, 2002, p. 144. This is a short book about fishing for salmon in the Upper Salmon and upper Middle Fork in the 1930s and early ‘40s. Written when they were old, to remember their mother, father and the fishing of their unforgettable boyhood summers, it is full of incident, history and quiet tenderness.
 Achieving Productivity to Recover and Restore Columbia River Stream-type Chinook Salmon Relies on Increasing Smolt-to-Adult Survival, Petrosky et al, North American Journal of Fisheries Management, 2020. Among the authors are scientists who have pioneered the use, and analytic power, of the smolt-to-adult return ratio.
 Comparative Survival Study of PIT-tagged Spring/Summer/Fall Chinook, Summer Steelhead, and Sockeye. 2019 Annual Report, Chapter Two, Table 2-10. Fish Passage Center. December 2019.