OPINION: Barging fish around the dams failed once; it would again

The Dec. 15 column in the Lewiston Tribune by Marvin Dugger, based on information provided by retired Army Corps of Engineers biologist John McKern, is so full of outdated and failed science that it’s hard to know where to begin a sensible rebuttal.

Their thesis is that transporting juvenile fish by barge is better than passing them to the ocean by more natural means, such as riding the spring runoff to the ocean as smolts evolved to do. They actually claim that spill programs now implemented over the eight dams between Idaho and the Pacific Ocean are harmful.

They could not be more wrong. Spill at the dams is good for migrating fish. In fact, it provides the safest passage method past the concrete — over spillway weirs (like water slides) or under radial gates — and spill has improved salmon and steelhead smolt-to-adult returns (SARs). Scientists also know that spill increases smolt survival by moving them more quickly past the eight dams between Lewiston and the ocean and by keeping them out of the smolt bypass systems that decrease SAR survival by 9% to13% for each dam that bypasses them.

How does spill decrease the amount of time it takes smolts to migrate through the hydropower system? Spill does not affect water transit time, but it reduces juvenile fish delay in the forebays of the dams and provides a non-powerhouse route of passage.

The three most important factors in smolt-to-adult return rates are:

Smolt travel time from the headwaters to the ocean (shorter time is better).

The number of times a smolt enters a powerhouse bypass system (less is better and never is best).

Ocean conditions. As percent spill increases, the first two of these important factors are improved. The third factor, ocean conditions, unfortunately cannot be affected.

As an example of the benefits of spill, with the provision of summer spill, fall chinook fish travel time from Lower Granite Dam to McNary Dam has averaged 11.9 days (2006-22). Prior to implementing summer spill, fish travel time in this reach was double that, averaging 23.1 days (1998-2005). Spilled smolts do not enter the bypass system, further increasing survival. Juvenile survival increased by 24% following the implementation of summer spill, from an average of 0.51 (1998-2005) to 0.63 (2006-22).

Recall that McKern’s favorite smolt migration strategy — during his tenure with the Corps and to this day — has been capturing smolts at upper dams and transporting them by barge for release below the lowermost dam, Bonneville. It was the centerpiece of federal salmon policy during the 1980s based on studies that compared smolt survival and SARs of barged fish with fish that passed through powerhouse bypass systems and then were released in the tailrace below dams. Especially under very low flow conditions, barging fish led to higher survival. However, even barging as many smolts as could be caught did not stop the decline of salmon runs, much less reverse that trend.

Implementation of the maximum smolt barging strategy did not consider spill as an option. By the 1990s, smolt survival and corresponding adult returns were so low that all Snake River salmon and steelhead runs required listing as threatened or endangered under the federal Endangered Species Act. Obviously, barging had not led to recovery of wild Snake River salmon and steelhead.

In 1994, an independent study titled “Transportation of Juvenile Salmonids from Hydroelectric Projects in the Columbia River Basin” concluded that “unless a minimal level of survival is maintained for listed species sufficient for them to at least persist, the issue of transportation (barging) is moot.”

Spilling smolts at the dams, which had been recommended by several biologists since the 1980s, was then included in further evaluations. Increasing spill, however, increased total gas saturation in the outflow of dams. Comparative survival studies, which have been carried out for over two decades, have determined that spilling an amount of water that would increase total dissolved gas (TDG) to as high as 125% did not have significant adverse effects on migrating smolts because when TDG levels are high, smolts migrate deeper in the water column where they are not physiologically affected. PIT-tagged (passive integrated transponder) smolts that were spilled over dams and passed through tail race waters with TDGs as high as 125% had better survival and adult return rates than did smolts which were captured in the smolt bypass system and barged to below all the dams. Annual comparative survival studies reports, including the recently released 2024 report, consistently corroborate these findings.

Smolt barging was a failed strategy that was insufficient to stop the decline of Snake River salmon and steelhead, much less rebuild those valuable runs. So if we want steelhead and salmon fisheries, spill programs should be maintained and improved wherever possible, up to the 125% total dissolved gas limit advocated by fish scientists.

None of the fisheries agencies of Idaho, Washington, Oregon and the tribes want to go back to the failed, obsolete science advocated by Dugger and McKern.

But, then, if spill is so beneficial, why have wild Snake River salmon and steelhead populations been unable to recover? In 2020, Bonneville Power Administration, the Corps and the Bureau of Reclamation presented a range of options for operating the Columbia River System in an environmental impact statement. They described the benefits for salmon and steelhead from each of several multiple objectives. They compared these multiple objectives to the existing management and selected a preferred option that included some increase in spill and predicted an increase in SARs for wild Snake River salmon and steelhead that were 35% and 28%, respectively. However, since SARs for wild Snake River salmon and steelhead had been only 0.8% and 1.6%, respectively, these increases in SARs are far below the recovery goal of 2% to 6% with a mean of 4%.

The range of multiple objective options included Multiple Objective 4, which would provide the greatest increase in spill resulting in a predicted 70% increase in Snake River salmon and steelhead SARs. Multiple Objective 2 maximized barging of smolts and minimized spill. Snake River SARs were predicted to decline by 30%.

You read that correctly. Maximizing barging actually decreased SARs — the opposite of what Dugger and his long retired Corps biologist have claimed. Multiple Objective Option 3 included breaching the four lower Snake River dams and increased spill at the four lower Columbia River dams. This option provided a predicted increase in SARs for wild Snake River steelhead and salmon of 170%, which would put these fish well on their way to recovery. This science has been developed and replicated multiple times during the past two decades by the most competent bio-statisticians of Idaho Department of Fish and Game, Washington Department of Fish and Wildlife, Oregon Department of Fish and Wildlife, the Columbia River Intertribal Fish Commission and the U.S. Fish and Wildlife Service. They present analyses and results annually in the comparative survival studies documents. These are available for anyone to read from the Fish Passage Center.

We ought to applaud political leaders who support spill, along with groups such as Idaho Rivers United and the Idaho Wildlife Federation that won court orders to create beneficial spill programs. Urge your leaders to do the same.

Scully, of Lewiston, served as a regional fisheries manager for the Idaho Department of Fish and Game. Williams, of Eagle, is an Idaho native who served on the Northwest Power and Conservation Council’s independent science advisory groups and authored two books on salmon recovery.