Questions and Answers about Snake River Salmonby Rocky Barker
The Idaho Statesman, June 5, 2001
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 replacement of natural runs with hatchery fish further reduced the diversity of the salmon. Salmon-spawning habitat was cut off by the dams and destroyed by development, grazing, logging and mining or pollution.
If Snake River salmon numbers were sustaining themselves in the 1960s, why did they fall?
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 ī70s coincided with a huge decline in productivity.
Both sides agree that salmon died 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.
Whatīs the major disagreement?
Scientists disagree 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 Idahoīs salmon.
And the fish all suffer the same effects from hatcheries, habitat destruction and harvests. Therefore, the delayed effects of collecting migrating salmon and barging them around the dams and the cumulative effects of migrating past the extra four dams are the major differences and likely responsible for the higher mortality of Snake River salmon.
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 their system for barging salmon around the dams has offset the damsī effects on downstream migration. Because their research shows that up to 98 percent of the salmon barged past the dams survive to the estuary, they argue that the extra mortality in Snake River fish is due to some other, unknown factor.
That could be competition from hatchery fish, habitat degradation, genetic effects or degraded ocean conditions that affect Snake River fish differently than lower Columbia salmon.
If future research shows few of the barged fish die as a result of their trip around the dams, the advantages of dam breaching are not so compelling. Thatīs because it would suggest something other than the four dams is affecting Snake River fish.
So why are the salmon in trouble with so many returning to Idaho this year?
The fish returning are mostly hatchery-raised and donīt spawn in the wild. The fish that are protected are those that spawn in rivers and lakes. Ocean conditions suddenly improved five years ago, and the increased productivity has aided both hatchery and wild salmon. Still, Snake river salmon are returning at rates four times lower than those in the Columbia River.
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