Many Questions Posed About Salmon, Dams
Faced with a mandate to restore endangered runs of salmon and steelhead, federal agencies are studying the possibility of mothballing four Snake River dams.
Here are answers to some of the most common questions about Snake River salmon and the dams. Sources include biologists, engineers and numerous studies written about the subject.
Which Snake River salmon and steelhead runs are in trouble?
All of them. Snake River coho salmon have been extinct since 1986. The river’s sockeye salmon were listed as endangered in 1991, and its chinook salmon and steelhead trout were listed as threatened in 1992 and 1997, respectively.
How many fish return to the river compared with historic levels?
Biologists estimate that 16 million salmon and steelhead once migrated up the Columbia River system each year. A big share went up the Snake.
Columbia River dams, fishing and loss of habitat have taken a heavy toll, but more than 100,000 fish still migrated up the Snake each year in the early 1960s.
Based on counts at the dams last year, 9,300 steelhead, 8,426 spring-summer chinook, 927 fall chinook and two sockeye migrated up the Snake.
Why not let the Snake River fish go extinct?
Treaties with the U.S. government give Northwest Indian tribes the right to harvest salmon from traditional fishing grounds.
People on both sides of the salmon debate predict the tribes will sue if the government doesn’t do everything possible to save Snake River fish. In a case settled this year, Avista Utilities agreed to pay the Nez Perce tribe $39 million for lost fishing opportunities caused by two Clearwater River dams removed in 1967.
Among the federal laws requiring perpetuation of fish runs are the 1973 Endangered Species Act, the 1976 Magnuson Fishery Management and Conservation Act, the 1980 Northwest Power and Conservation Act and 1980 revisions to the Federal Power Act.
How do dams on the Snake and Columbia rivers harm salmon?
Young salmon, called smolts, historically rode a crest of spring runoff from the mountains to the ocean. The dams slowed the flow, doubling the time required for that trip. Some scientists believe that exhausts the smolts and complicates their adaptation to salt water.
Fish that go through dams can be killed by turbines. Fish spilled over dams sometimes suffer a condition similar to the bends.
Water in reservoirs behind the dams sometimes gets much warmer than a natural river. Smolts in both the Columbia and Snake rivers died last summer when some reservoirs soared well above the 68 degrees mandated by federal Clean Water Act.
Earlier this month, a group of scientists reported to the Northwest Power Planning Council that high temperatures in reservoirs leave some adult salmon too exhausted to spawn when they return from the ocean. Some adults climb fish ladders only to be sucked back through the dams, the report said.
The reservoirs also leave smolts vulnerable to predatory fish and birds.
Can we successfully barge fish around the dams?
The Corps of Engineers now collects about half of the smolts that reach the first dam, Lower Granite. The young fish are put in barges for transport around the Snake River dams and four more on the Columbia.
Scientists say about 98 percent of the smolts survive the trip, compared with about 50 percent survival for those left in the river.
Then why not increase barging?
That is one of the proposals biologists are studying.
Critics say that despite the high survival rate in barges, fish from the Snake River are not returning from the ocean in high enough numbers to perpetuate the runs.
The return rate for spring chinook salmon is about one-quarter of 1 percent (250 adult fish returning to the river for every 100,000 smolts that go to sea). Biologists say that to restore the runs, the return rate should be at least 2 percent.
What does the rate of return from the ocean have to do with barging and dams on the Snake?
Many scientists note that return rates are higher for similar fish runs on other Columbia River tributaries. They theorize that whisking smolts into crowded barges or making them swim through eight reservoirs causes so much stress that the fish die later.
A minority of scientists who have studied the issue debunk the “delayed mortality” theory and say the fish are dying from unfavorable ocean conditions or other factors.
Can’t we make the dams safer for salmon?
The dams are much safer now than when they were new. The corps proposes spending $360 million over the next five years making dams on the Snake and Columbia rivers safer still.
What does dam breaching mean?
The dams are built primarily of concrete and steel. As a final step of construction, rock was dumped into channels where the river flowed around each dam. Breaching means removing those rock abutments so the river can flow free. The abutments could be replaced - at an enormous cost - if society decided to put the dams back in use.
How much would breaching cost?
The latest corps estimate is $800 million to $1 billion, including the cost of changing roads, water systems, railroad tracks and other affected infrastructure.
That does not include the economic impact on surrounding communities. Nor does it include the money saved by ending some salmon-restoration projects, or the value of the fish themselves.
The BPA says that customers who pay $55 a month for electricity would see their bills climb to between $57 to $60 a month.
What would happen to the sand and silt trapped behind the dams?
Engineers estimate that 100 million to 150 million cubic yards of sediment is trapped, primarily behind Lower Granite Dam. That’s enough to cover Spokane’s Riverfront Park and downtown shopping district to a depth of 100 to 150 feet.
Engineers speculate that after breaching, half the sediment would settle in the Columbia River behind McNary Dam. Most likely, it would not be enough to disrupt barge traffic.
Exactly how the sediment would affect fish depends on the timing of the breaches. Salmon can handle dirty water for short periods. But silting can leave spawning beds unusable, at least until the gravel is washed clean by the river.
Would breaching lead to more severe flooding?
No. The Snake River dams were not designed for flood control.
How would breaching Snake River dams help the fish if they still have to survive four Columbia River dams?
Biologists say Snake River fish runs declined dramatically, then stabilized, after the government built the four lower Columbia River dams. The runs plummeted after the four Snake River dams were built, and have continued to decline.
By comparison, the Hanford Reach chinook salmon run, which must negotiate only the four Columbia River dams, remains healthy.
The corps is studying whether to breach John Day Dam on the lower Columbia River, or lower the reservoir behind it. That study is far behind the Snake River debate.
In addition, Congress next year may approve money to study drawing down the reservoir behind McNary Dam, and for making all four lower Columbia dams - McNary, John Day, The Dalles and Bonneville - less lethal to salmon.
Have hatcheries hurt the Snake River runs?
Sixteen hatcheries have been built to make up for losses caused by the lower Snake River Dams, Hells Canyon Dam upstream and Dworshak Dam on the Clearwater River, a Snake River tributary. The reviews are mixed.
Some biologists worry that hatchery fish are exposing wild fish to kidney diseases and other ailments, especially when the fish are confined to barges.
Idaho biologists concluded that the hatcheries have not significantly weakened the genetic makeup of wild fish. They note that the hatch rate for eggs - a key indication of genetic problems - has not declined since the hatcheries opened.
Isn’t predation by birds a big problem?
Scientists say as many as 27 million salmon smolt may be eaten each year by Caspian terns at the mouth of the Columbia River. Together with cormorants and gulls, the birds may gobble as many as 20 percent to 40 percent of fish trying to leave the river.
Some scientists say Snake River fish are especially vulnerable because they’re weakened by the dams or barging. The corps is spending $760,000 attempting to move the birds to another island, where biologists hope the salmon smolt will be less vulnerable.
What about marine mammals?
The West Coat sea lion population has grown about 5 percent a year - to 170,000 animals - since passage of the 1972 Marine Mammal Protection Act. Other marine mammals have seen similar growth.
Biologists say as many as 40 percent of the mature salmon that return to the Columbia River have bite marks. Some Snake River salmon may also be eaten by Puget Sound killer whales.
“The incidence of severe bites is actually pretty low,” said Ed Bowles, anadromous fish biologist for the state of Idaho. “The working assumption right now is that marine mammals are killing a small portion of the fish.”
Do fishermen still kill Snake River salmon and steelhead?
Yes. The hardest hit are fall chinook. The National Marine Fisheries Service estimates that until recent years 35 percent to 40 percent of Snake River fall chinook that reached adulthood were caught by Canadian commercial fishermen. That number has dropped dramatically since Canada has imposed severe restrictions to protect its own chinook runs.
Of the fall chinook that return to the Columbia, about a quarter are captured by tribal fishermen, according to Oregon biologists.
Fall chinook are vulnerable because they mix with other, healthier runs. Eliminating the river catch would mean stopping commercial harvest of surplus Hanford Reach fall chinook.
The only other threatened fish caught in significant numbers come from a run of large steelhead, most of which are destined for the Clearwater River, a tributary of the Snake. About 30 percent of that run was captured by the tribes, but the limit was reduced to 15 percent last year.
Since 1986, Columbia and Snake River sports fishermen have been prohibited from keeping wild steelhead, although some undoubtedly are caught and killed. Infrequent Snake River sports seasons for chinook salmon target only hatchery fish.
As recently as the 1960s, fishermen on the ocean, and along the Columbia and Snake rivers caught 60 percent of Idaho’s wild salmon and steelhead. The figure since has dropped to less than 10 percent.
Has El Nino hurt the fish?
Fish runs suffer if rivers run warm and sluggish. That happens when El Nino brings low snowpacks in the mountains.
A bigger problem, which scientists say may not be related to El Nino, is a long-term shift in ocean currents that creates food shortages for salmon. History suggests these shifts occur about every 30 years, and that the current may now be growing more favorable for Northwest salmon.
Some biologists believe ocean currents, which turned sour about the time the Snake River dams were constructed, are a major reason salmon runs declined. If that were the case, other researchers say, then similar runs from other Columbia River tributaries would be equally affected. Preliminary research suggests that hasn’t happened.
If dams are the problem, why are salmon on some undammed streams doing poorly?
The journal Fisheries reported in 1996 that about 100 runs of salmon and trout in the Northwest and northern California have gone extinct since the time of European settlement. Perhaps 200 others are in serious decline.
Biologists say the reasons vary from river to river, but include dams, habitat degradation, pollution, water diversions, urbanization and competition or predation by non-native species.
The journal also identified 99 steelhead and salmon runs (including 64 in Washington) that are still healthy. They include two Eastern Washington runs: Fall chinook from Hanford Reach of the Columbia River and sockeye salmon from the Wenatchee River. No Idaho runs made the list.
The report’s authors worried that the healthy runs will suffer while biologists concentrate on restoring endangered fish runs.