Environment

Remove 4 dams, leave these fish alone, and they may be able to replenish themselves

More from the series


20 years later, Idaho's salmon are still in danger of disappearing forever

The salmon of the Northwest are the stuff of legends. Pioneers talked of rivers so thick that they were tempted to cross on the backs of the fish. But times have changed, the fish's numbers have plunged, and 13 species were placed on the endangered species list by 1995. Climate change and our network of hydropower dams have helped thwart attempts so far to find a sustainable solution. And it's possible some of our strategies - including our reliance on hatcheries - have backfired.

Expand All

It’s in places like Marsh Creek where the hope rests for spring chinook and other Northwest salmon.

No hatchery-born fish have ever sullied the genetic stock of the chinook that run in the clean, clear waters of the 15-foot-wide tributary of the Middle Fork of the Salmon River, 10 miles west of Stanley and 870 miles from the ocean.

The DNA of these salmon carries the imprint of 10,000 years of adapting to this watershed. Their range of traits and diversity allows them to survive incredible odds and obstacles as they migrate downstream, then return from the ocean to spawn in their native waters. Natural selection has equipped these fish to face the longest, highest migration of any salmon in the world.

These native fish in Central Idaho’s pristine habitat are in the worst shape since 1995, when no chinook returned amid some of the worst recorded Pacific Ocean conditions for salmon, and 2015, when low river flows devastated their numbers.

But the habitat of Marsh Creek is, if anything, better than it was in the 1960s, when nearly 2,000 wild fish returned to spawn annually.

That’s why the wide majority of fisheries biologists believe these salmon can rebound quickly if four dams on the Snake River — half of the eight that stand between Idaho and the Pacific — are removed.

Their evidence: When Marsh Creek’s chinook had ideal ocean conditions and high river flows that helped them cross the dams safely, they returned at levels like before the dams were built. When those conditions changed, the chinook returned to their current track to extinction.

Diverse life cycle

The Marsh Creek salmon quit eating when they begin running up the Columbia in March; only the strongest make the trip back to the very riffle where they emerged as fry two, three, four and even five years before. The female salmon spawn by beating their tails into the gravel to make a redd, or nest, for their eggs.

Most newborn fish stay in the creek for a year before they quit swimming against the flow and allow it to carry them downstream during the spring runoff.

Some do migrate early down into the Middle Fork and even the main Salmon River, giving them a head start and another survival advantage. Some stay in Marsh Creek for two years.

By comparison, hatchery salmon are all released at once and have little of the diversity that natural selection provides.

The Middle Fork of the Salmon River has long been identified as a center of salmon production in the Columbia watershed. In the 1940s, when only one dam stood between the Pacific and Idaho, biologists counted 23,000 redds there.

This year Idaho Department of Fish and Game biologists and volunteers counted only 52 redds — better than 1995, but far below historic and sustainable levels. Since 1995, about half of salmon leaving the Snake River Basin died as they migrated as smolts through the eight dams, according to the National Oceanic and Atmospheric Administration Fisheries Service. That has improved in recent years to about 40 percent due to improvements made at the dams.

Variations in how long the chinook stay in Marsh Creek and roam the ocean give the population a buffer to survive back-to-back bad years. Some fish may leave Marsh Creek after one year, then return from the Pacific after two. They share the river with fish with the same life history, but that emerged from the gravel a year later, or chinook that spend two years in Marsh Creek and three in the ocean.

Since a Marsh Creek spring chinook can lay 5,000 eggs, they can quickly rebound if conditions are right.

These salmon have a high risk of going extinct if conditions downstream from the Middle Fork — the dams, predators like sea lions, the poor ocean conditions and climate change — don’t improve, said Russ Thurow, a U.S. Forest Service Rocky Mountain Research Station scientist.

But, he said, when river flows are high and ocean conditions are ideal — cool, nutrient-rich waters that provide salmon with abundant food and fewer predators — the salmon in Marsh Creek and throughout the Middle Fork demonstrate what their wild heritage can produce.

From 1996 to 2000, the Middle Fork chinook had these ideal conditions, and they responded. From 2001 to 2003, the Middle Fork redd count exceeded 1,600 annually and reached more than 2,200 at its peak. Extreme low river flows from 2001 on and less favorable conditions in the Pacific sent the trend downward, to where it is today.

The dam argument

That response shows what could happen if the four dams on the Snake River are removed, said Rick Williams, an independent fisheries biologist from Meridian. The American Fisheries Society’s Western Division, the Nez Perce and biologists elsewhere make the same argument about the entire Snake Basin.

Even if dam managers simply allow as much water as possible to spill over the dams rather than pass through hydroelectric turbines, these biologists believe Snake River Basin salmon returns will grow by 100 to 300 percent.

The U.S. Army Corps of Engineers operates the eight Snake and Columbia dams. It has developed spillway devices that make salmon migration downstream easier, without spilling as much water away from hydroelectric turbines that produce power. Its experts believe these have made a major improvement in fish survival, and doubt that dramatic improvements are possible, especially with ocean conditions turning poor.

“Personally, I don’t see how the numbers add up,” said Dan Feil, a fisheries biologist with the Army Corps. “I’m a skeptic.”

Marsh Creek is not Williams’ only example. When the devices were added and other changes were made in the Columbia dams over the last 15 years, sockeye salmon upstream in the Okanogon River in north-central Washington and British Columbia rebounded to runs of more than 600,000 fish at Bonneville Dam. More than 200,000 were counted in the river and on Osoyoos Lake in 2014.

He also points to the high annual returns of wild fall chinook that spawn in the last free-flowing stretch of the Columbia River known as the Hanford Reach. Those wild salmon are responsible for the river’s best fishery.

Other examples: Alaska’s Bristol Bay, a huge natural fishery; and Russia’s Kamchatka Peninsula, a California-sized region that was kept wild by the Cold War until the early 1990s.

“We have so few examples of fish demonstrating their potential and fecundity and diversity in any kind of pristine habitats that people don’t know what they can do,” Williams said. “We’ve lost our faith in the fish and in nature to take care of themselves.

“If we could start thinking about the concept of salmon and steelhead conservation areas, you don’t have to do anything else but make sure you don’t screw it up.”

Rocky Barker: 208-377-6484, @RockyBarker

Editor’s note

The Northwest is still struggling to figure out a sustainable plan to save imperiled salmon. This is part of a continuing series exploring whether salmon can ultimately survive.

Related stories from Idaho Statesman

  Comments