the film
Commentaries and editorials

Sound Science and Experience
Refute Dugger's Fish Story

by Steve Pettit and Richard Scully
Lewiston Tribune, August 14, 2021

In order to rebuild Snake River salmon and steelhead resources, the fish must
migrate in the river and the four lower Snake River dams need to be breached.

In retrospect, the number of returning adult salmon was relatively level from 1938 through 1990.  The precipitous loss of returning chinook entering the Snake River (Figure 20) accounts for a major share of the decline that has occurred in total return to the Columbia -- Artificial Production Review, NW Power & Conservation Council The Aug. 1 Commentary by Marvin Dugger was indeed an opinion, and that is all. Dugger contends that if the Snake River dams are breached, then smolt collection and transportation will be impossible and smolt numbers will crash. Fisheries data, analyses and well-documented histories do not support this conclusion.

Additionally, if the Snake River dams were removed, Dugger opines that Idaho's fish hatcheries and management programs would "go away" for lack of funding. This is not supported by reality. The hydropower from the rest of the basin's 27 federal dams, which the Bonneville Power Administration markets, produces all the funding that these programs might require. We use the word "might" because dam removal may improve survival to the point where hatchery production could be cut back significantly.

The crash Dugger worries about has already happened.

In the 1990s, all populations of Snake River salmon and steelhead were listed under the Endangered Species Act. Why did this happen?

Because the construction and operation of the four lower Snake River dams simply kills too many fish. The development of the smolt transportation program was an expensive attempt to mitigate the lethal effects of these dams on Snake River fish. This recognition that the dams are a disaster for Idaho salmon and steelhead was the reason the smolt transportation program was developed through the 1970s and changed from research to a management program.

From 1981 to 1992, approximately 90 percent of all Snake River salmon and steelhead were transported. After 10 years of maximizing smolt transportation, these populations were in such dire straits that ESA listing became necessary. Clearly, the smolt transportation program did not work.

At present, most of the smolts that enter a dam's powerhouse are screened away from turbines and shunted through a bypass system to an awaiting barge for transport. Fisheries managers attempt to maximize the number of smolts that avoid the powerhouse and pass over the dam's spillway since each powerhouse passage reduces smolt to adult return rate by 9 percent to 13 percent. It can happen eight times.

Dugger cites an 11-times greater return of barged fish than nonbarged fish from a 1983 study. This study, which was done on the Tucannon River, found that 11 times more adults from transported smolts returned to Bonneville Dam than from nontransported smolts. But none of the study fish -- transported or not -- returned as adults to the Tucannon River. Smolt transportation impairs homing of returning adults and is of little value if fish do not return to their place of origin.

Considerable research has been done since the 1983 study. Scientists agree that the smolt transportation program does not mitigate for the adverse impacts of the four lower Snake River dams. Adult salmon that were transported as juveniles have a slower upstream migration rate, have lower survival, have a higher stray rate and less resiliency in high water temperatures than nontransported smolts.

None of Dugger's fish transportation opinions are supported by facts.

After spending billions of dollars trying to recover salmon and steelhead by transporting smolts around the lower Snake River dams, the fish remain ESA-listed and declining in numbers. This strategy has been tested and failed.

In order to rebuild Snake River salmon and steelhead resources, the fish must migrate in the river and the four lower Snake River dams need to be breached.

Dugger reported that from 2000 to 2009, there were 313 percent more steelhead and 273 percent more spring chinook counted at Bonneville Dam than in the decade of 1938 to 1947 when Bonneville was the only dam between Lewiston and the Pacific Ocean. In the early decade, all fish were wild, while in 2000 to 2009, only 27 percent were wild.

Also, during the earlier decade, fisheries harvested a minimum of 64 percent of chinook and 54 percent of the steelhead below Bonneville Dam. Recent harvests below Bonneville Dam have been 5 percent to 10 percent of the runs. If the percent of harvest had been the same in 1938-47 as it is now, the early dam counts would have been more than twice as large.

There have been a few large runs in recent years even with eight dams between Lewiston and the ocean. These occur only when both ocean and in-river conditions are highly favorable. Such events are rare and likely to become rarer in the climate-impacted future, especially so as fish populations decline to dangerous levels.

Snake River salmon and steelhead need two to six adults to return to the Snake River for every 100 smolts that migrate to the sea to sustain their populations. This is the smolt-to-adult (SAR) return ratio.

Snake River spring chinook and steelhead, which must negotiate eight dams, now average SARs of between 0.8 percent and 1.6 percent.

Fish from the John Day and Yakima rivers, which enter the Columbia River upriver from three and four dams respectively, have SARs greater than 2 percent now. Note that those fish experience the same ocean conditions, harvest and predators as do Snake River fish. The difference in survival is due only to Snake River fish suffering the additional negative impacts of passing four lower Snake River dams.

Except for Lower Granite Reservoir, which receives summer cool water inflow from Dworshak Reservoir, the three lowest Snake River reservoirs become very warm from top to bottom. Midsummer surface temperatures are in the mid-70s. Ice Harbor and Lower Monumental reservoirs are 70 degrees at the bottom.

The river from Lewiston to Pasco is 140 miles long and drops in elevation 387 feet, an average 0.05 percent gradient. Dugger says that it is easier for fish to swim through reservoirs and climb ladders than swim in the river. He is wrong. The same amount of energy might be expended. But in slackwater reservoirs, there is much more stress for returning adults from hot water in fish ladders. Adults delay below the dams, sometimes for days, before ascending the ladders. Additionally, the slow flow in the reservoirs greatly increases travel time for smolts heading to the ocean. It takes about 10 times longer in reservoirs, wasting scarce energy reserves and increasing exposure to predators.

Related Pages:
Saving Salmon is a Ruse for Breaching Our Dams by Marvin F. Dugger, Lewiston Tribune, 3/14/21
What About the Dams? by Marvin F. Dugger, Lewiston Tribune, 11/3/19

Steve Pettit is a retired Idaho Fish and Game Department fisheries research biologist.
Richard Scully served as a regional manager for Fish and Game.
Sound Science and Experience Refute Dugger's Fish Story
Lewiston Tribune, August 14, 2021

See what you can learn

learn more on topics covered in the film
see the video
read the script
learn the songs
discussion forum
salmon animation