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Questions and Answers about Salmon

by Rocky Barker
The Idaho Statesman, July 20, 2000

How did salmon numbers fall from their historic high of 8 million to 16 million to fewer than 1 million in the 1990s?

Nearly all scientists agree that relentless commercial fishing of salmon stocks from 1866 to 1930 dramatically reduced the number of salmon and the diversity of salmon species in the Columbia River Basin. The building of dams and the replacement of natural runs with hatchery fish further reduced the diversity of the salmon. Salmon spawning habitat was cut off by the dams, destroyed by development, grazing, logging and mining, or polluted.

If Snake River salmon numbers were sustaining themselves in the 1960s, why aren't they now?

Scientists on both sides of the issue agree that the building of the four dams on the Snake River and the last dam on the Columbia River in the 1960s and '70s coincided with a huge decline in productivity.

Both sides agree that dams killed salmon both at the dams and afterward in the Columbia River estuary and the ocean, because of stress or other factors. They also agree that the extra mortality is higher in Snake River salmon than in Columbia River salmon.

Both sides agree that a downturn in ocean conditions, which reduced salmon productivity, occurred since the mid-1970s.

Both sides agree that salmon that spawn in lower Columbia River tributaries and the river itself return to spawn at higher rates than do those that spawn in the Snake River.

What's the major disagreement?

Scientists don't agree on why more Snake River salmon die in the estuary and ocean than lower Columbia River salmon.

What is the majority opinion?

State, tribal, and U.S. Fish and Wildlife Service biologists say that the four Snake River dams and the barging and fish bypass systems are responsible for the extra mortality.

They say the difference in return rates between lower Columbia and Snake River salmon is evidence that the four extra dams on the Snake are the limiting factor for Idaho's salmon. Both the Columbia and Snake River salmon and steelhead must face the same estuary and ocean threats, such as fish-eating birds and ocean predators.

And they all suffer the same effects of hatcheries, habitat destruction and harvests. Therefore, the delayed effects of barging and the cumulative effects of migrating past the extra four dams are the only major differences and are responsible for the extra mortality of Snake River salmon. To show that barging works, the data must show that barged salmon survive in the ocean as well as or better than those that migrate in the river, and that the extra mortality is not due to the dams.

These scientists conclude that breaching the dams is the best and perhaps only way to restore the productivity of Snake River runs.

What is the minority opinion?

Scientists from the National Marine Fisheries Service, the U.S. Army Corps of Engineers and the Bonneville Power Administration say the system they developed to collect and barge salmon around the dams has offset the downstream migration problems that caused salmon to decline when the dams were completed. Since their research shows up to 98 percent of the salmon barged past the dams survive to the estuary, the extra mortality in Snake River fish is due to some other, unknown factor.

It could be competition from hatchery fish, habitat degradation, genetic effects or degraded ocean conditions that affect Snake River fish differently than they affect the lower Columbia salmon.

If new research shows few of the barged fish die as a result of their trip through the dams, the advantages of dam breaching are not so compelling, because it would suggest something else is affecting Snake River fish more than the four dams.

These scientists say that reductions in hatchery fish releases, predator control, additional harvest reductions, stricter habitat restrictions, improving dam passage survival and increasing flows by releasing more water from Idaho reservoirs can restore salmon productivity enough with the dams in place, especially now that ocean conditions have improved.

So why are the salmon in trouble with so many returning to Idaho this year?

The fish returning are mostly hatchery-raised and don't spawn in the wild. The fish that are protected are those that spawn in rivers and lakes.

Rocky Barker
Questions and Answers about Salmon
The Idaho Statesman, July 20, 2000

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