Salmon & Steelhead Habitat
Taking an Ecosystem Approach to Habitat Conservation & Restoration
Salmon are keystone species in the Northwest and play a major role in sustaining healthy river ecosystems and more than 130 plant and animal species. Their migration is an epic journey that can span more than 900 miles, from spawning sites high in the mountains to the ocean and back. To thrive, they need specific habitat features: clean and cool water, streamside vegetation, clean gravel beds, and ample food. By protecting the watersheds that sustain salmon, we also protect forests, food, water, communities, and economies.
The Issue at a Glance
- Hydropower, irrigation diversions, and other industry developments have substantially decreased river flows
- Salmon are cold-water fish. Waters over 68°F can be lethal
- Industry has polluted many Northwest waterways, resulting in poor water quality
- Wetlands and estuaries, critical transition zones for salmon, have declined dramatically (over 74% on the Columbia River).
- Increased high-intensity wildfires and logging have degraded stream channels and salmon spawning habitat.
Pristine Habitat for Salmon
Salmon are anadromous fish that require clean, cold, flowing freshwater to survive. From fry to spawning adults, salmon rely on freshwater streams, rivers, and estuaries during migration. They need healthy riparian areas that can filter pollution and provide vegetation for feeding and resting during their journey, as well as gravel beds for spawning.
A little water can go a long way during sweltering summers. Dry summers creates slow-moving, warm water that reduces the oxygen available for salmon to breathe and increases water turbidity, impacting their ability to navigate.
Industry in the Columbia River Basin has caused significant pollution. A 2009 EPA report found that the Columbia River has toxic levels of heavy metals, flame retardants, and polychlorinated biphenyls (PCB), further pressuring at-risk salmon. Removing chemicals like DDT and PBCs from the Portland Superharbor Fund Site can potentially increase salmon returns to the Willamette River by up to 20%.
Climate change and dams have contributed to increased water temperatures that in some rivers, can prove fatal. Well-distributed Coldwater refuges are crucial for salmon and steelhead migrating upstream, as they serve as pits stop for fish to rest.
A 2020 EPA report found the lower Snake River dams to be the primary source of heat pollution in the Columbia River system. From July through October, water temperatures frequently surpass 68°F, the temperature threshold salmon can survive in.
Streamside vegetation slows runoff, protecting the banks from erosion and preventing heavy flows of silt from entering the stream, providing clean water for salmon. Healthy riparian vegetation also provides shade for salmon and woody debris for the stream, which provide protection from predators, cool resting pools, and feeding grounds.
Riparian buffers are ribbons along the stream that are protected from logging or other industrial uses. For spawning grounds, scientists recommend that these buffers should be at least 100 feet.
Salmon need free-flowing water to support timely migrations and tolerable water temperature. Substantial water withdrawals and flow management to support irrigation, hydropower, and municipal uses coupled with shifting precipitation patterns due to climate change, many rivers face slower stream flows. Fish passage, spillover, and truck or barge transport have been used to decrease the time it takes for salmon and steelhead to pass through dams, but these methods cause stress and contribute to latent mortality.
Female salmon search for cool and shallow streamside pools and riffles to lay their eggs. They need clean, stable gravel, and good flow to support oxygenation for redds (salmon nests). Along with all of the other threats listed here, flooding and wildfire pose risks to critical spawning habitats.
Salmon migrate through estuaries twice during their lifetime and rely on the brackish water to transition physiologically between freshwater and saltwater. Coastal wetlands line the shore of estuaries and are host to diverse habitats that provide food for salmon.
Both estuaries and coastal wetlands have significantly decreased in size, making it harder for salmon to transition and forage for food. They must expend more energy because they have to compete for fewer food sources. Restored estuaries increase food and insects for foraging salmon during a time of rapid growth and have been shown to increase salmon survival once they enter the ocean.