This week, we continue further down the coast to explore the Columbia-Snake Rivers and their connection to northwest salmon and Southern Resident orcas.
Historical salmon data for The Columbia and Snake Rivers estimates that 10-16 million wild salmon and steelhead entered the Columbia River Basin to spawn, annually, with 2-4 million more utilizing the Snake River watershed. The Columbia River Basin was once home to the largest runs of Chinook salmon in the world, and roughly half of those Chinook returned to the Snake River in the spring and fall seasons about 200 years ago. Today, less than 1 million fish return to the Columbia River, and fewer than 60,000 wild fish return to the Snake each year.
What began the downfall of salmon populations in this river system?
Largely, the establishment of salmon canneries in 1867 was the first cause of decline in wild salmon populations. In 1879 it was reported that over half a million salmon, with an average weight of 22 pounds, were caught and canned in a single season. At the turn of the century, widespread concern for catch rates of salmon caused the people of Oregon to pass two laws limiting fishing on the Columbia and other rivers. While efforts to curb overfishing (by also banning seine netting) continued into the late 1940s, major modifications to the Columbia and Snake Rivers were also in progress in the form of dams and hydrosystem facilities to generate power, provide flood control, and irrigation options for farming.
Hydrosystem Complexities for salmon on the Columbia-Snake River: Dams and Salmon Don’t Mix
Dams built in the 1930s and 1950s along the Columbia River, and dams built in the 1960s and 1970s along the Lower Snake River, have impeded salmon from reaching their northernmost and easternmost spawning sites, since. By 1986, Snake River Coho were extinct. Today, all surviving Snake River salmon populations are listed under the Endangered Species Act and threatened with extinction. Per the Endangered Species Coalition, “On average, there is a major dam every 72 miles in the Columbia River Basin. The upper stretches of the Columbia and the Snake rivers are impassible at the Chief Joseph and Hells Canyon dams, respectively. But salmon can navigate past some other dams.
Four federal dams managed by the Army Corps of Engineers on the lower Snake are built with fish ladders for returning adult salmon, but out-migrating juveniles (smolts) have a very difficult time getting to the ocean.”
The nine dams along the Columbia prior to reaching Chief Joseph dam, and eight dams along the Columbia-Snake prior to Hells Canyon present massive challenges to both inbound and outbound salmon. Out-migrating salmon smolts have a perilous journey, as they must navigate through a series of hydrosystems, dam turbines, sluiceways, stagnant reservoirs, warming waters, contaminants, and various predators before reaching the Pacific Ocean.
Even if a juvenile salmon manages to reach the Pacific Ocean against these odds, there may still be ramifications leading to mortality due to the stress of navigating these hydrosystems.
While complex in nature due to a degree of variables, fish Biologists and scientists that have studied Columbia-Snake River smolts have discovered that the hydrosystem stressors experienced by out-migrating juveniles may also likely cause some salmon a delayed mortality. Hydrosystem stress on salmon leads them to delay their development and suppress their immune systems, as more energy is channeled into survival, instead. Entering the ocean in a weakened condition can increase the chance that these salmon will be susceptible to disease, parasites, or may not successfully adapt to the saltwater environment. Even if they make it downstream through each aspect of the hydrosystem, they still may not become a viable specimen in their ocean environment. Which also means they will not become accessible orca food.
Actions To Bring Wild Salmon Back to the Columbia-Snake River System:
According to Wild Orca, “NOAA Fisheries, the federal agency charged with protecting both endangered orcas and endangered salmon, has described the decline of Columbia Basin chinook salmon as, “[p]erhaps the single greatest change in food availability for resident killer whales since the late 1800s...”
Whale and Dolphin Conservation adds, “Breaching the Snake River dams, in combination with increased spill (water flow) through other dams in the Columbia River Basin, provides more certainty of long-term survival and recovery for wild Snake River Chinook salmon than any other measure… Removing the dams and increasing spill would help the river system return to more natural conditions, which can help increase survival of wild Snake River Chinook salmon to the point of rebuilding healthy populations – something that the federal agencies themselves recognized in their recent review of dam operations.”
To read more details about the 2020 Federal EIS Report, follow this link: For first time in 20 years, feds take deep look at hydroelectric dam removal on Lower Snake River | The Seattle Times
Resources: https://us.whales.org/deep-dive-snake-river-dams/ | https://www.endangered.org/orca-salmon-and-rivers/ | https://www.columbiariverkeeper.org/columbia/salmon-and-steelhead#:~:text=The%20Columbia%20River%20Basin%20once%20produced%20more%20salmon,number%20declined%20to%20less%20than%201%20million%20fish. | https://www.idahorivers.org/lsrd | https://today.oregonstate.edu/archives/2008/oct/new-study-salmon-smolt-survival-similar-columbia-and-fraser-rivers | https://www.wildsalmon.org/images/factsheets-and-reports/2015-SOS-FS-CB-salmon-status.pdf