The year was 1911. The so-called Progressive Era in the United States was coming to an end, as President William Howard Taft pushed the Republican Party to the political right in opposition to former president Theodore Roosevelt. Two years earlier, President Roosevelt, who led the Progressive wing of the party, created Mount Olympus National Monument — later to become Olympic National Park.

In September of 1911, Clallam County Sheriff James R. Gallagher visited the construction site of a new dam being built on the Elwha River, which flows swiftly out of the Olympic Mountains near Port Angeles. The sheriff was shocked to see, at the base of the future dam, a multitude of salmon “packed in together like a school of herring or sardines in a box,” according to his report to the Port Angeles Olympic Leader, the local newspaper.

What the sheriff observed was a mighty river being diverted for dam construction and shooting like a firehose through a man-made flume. Hundreds, if not thousands, of large migrating salmon were trapped in the pool below. The dam would bring an end to the massive migration of salmon up into a mountainous watershed capable of producing the legendary Tyee, a breed of Chinook salmon that occasionally grew to 100 pounds or more.

“Every few moments a big fellow makes a jump clear of the water that shoots out of the flume as though from a hydraulic nozzle and strikes square in the flume above, only to be thrown back to the pool below,” states the newspaper article. “Mr. Gallagher says he does not believe a single fish can get through… He has seen big Spring or Tyee salmon thrown fifty feet the moment their noses touched the water.”

For years, the Elwha Dam was heralded for its power production. But with no provision for fish passage, eight species of migrating salmon and trout were blocked from more than 70 miles of productive habitat upstream, causing the salmon runs to decline. A further blockage was added in 1927, when the Glines Canyon Dam was built eight miles farther upstream. Both barriers would remain in place until the dams were removed, starting in 2011.

When the Elwha salmon were first cut off from the upper watershed, the study of modern genetics was in its infancy, as leading researchers studied fruit flies to understand how unusual traits were passed from one generation to the next. Although Sheriff Gallagher and many others worried about the salmon runs, nobody contemplated how the new dam might isolate aquatic populations, alter their genetic makeup, and potentially extinguish ancient salmon stocks.

Now, thanks to cutting-edge genetic techniques, researchers have been piecing together the intricate genetic makeup of salmon before and after dam removal. They have identified, for example, some slight differences in the genome of certain populations confined above the upper dam versus those below the lower dam, with another identifiable group found between the dams.

The genetic makeup of fish, along with environmental factors, sets the stage for a lifetime. Genes influence the growth rate of fish and their ultimate size; they affect the rate of metabolism and demand for food; and they regulate immune function and the ability to fight off disease. Genes also play a role in many behavioral traits, including predator avoidance and decisions about staying home or swimming out to sea.

Understanding genetics can help fish and wildlife managers protect individual populations, preserve genetic diversity, and ensure the existence of a variety of species — right up to top predators such as humans and killer whales. Advanced genetic analysis can be used to trace the origins of recolonizing fish, understand their movements, and identify the parentage of survivors as the population recovers.

Among many recent findings in the Elwha, it appears that a number of the rainbow trout trapped above the dams somehow retained the genes for early migration. As such, these rainbow trout are taking on the anadromous characteristics of migratory steelhead, and experts say these early-migration genes — obscured for a century — may be a key factor in the rapid recovery of steelhead now seen in the upper Elwha watershed. (Rainbow trout and steelhead are two life-history forms of the same species, Oncorhynchus mykiss.)

“What we have seen is a reawakening of life histories for species in the Elwha,” said George Pess, supervisory fish biologist at NOAA’s Northwest Fisheries Science Center who helps oversee federal research on the Elwha. “It is a dance between genetics, ecology and evolution.”

As the studies continue, researchers are recording the rebirth of migratory populations, including Chinook, coho, sockeye, pink and chum salmon, as well as steelhead. Other intriguing changes are being seen among bull trout, cutthroat trout and lamprey.

“All nine migratory fish runs passed the former Elwha Dam within 31 months, and eight of the nine ascended through Glines Canyon within 60 months,” according to a study led by Jeffrey Duda of the U.S. Geological Survey in Seattle. “Native anadromous salmonids were documented up to 40 kilometers (25 miles) upstream of the upper dam and in approximately 8 kilometers (5 miles) of novel river reaches contained in the footprint of the former reservoirs.”

As fish populations grow and recolonize every recess of the watershed, scientists are uncovering the genetic mysteries of evolution. Much remains to be discovered, including the answer to this provocative question: Do any of today’s Elwha Chinook have the wherewithal to become one of the legendary 100-pound Tyee?

Up next: Wild steelhead still a force in the Elwha.