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SCORE

3.1

MODERATE

Southern Oregon/Northern California Coast Chinook Salmon

Oncorhynchus tshawytscha

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At a Glance

Southern Oregon/Northern California Coastal (SONCC) Chinook salmon in California are limited to only a few watersheds, but populations remain stable. They may be vulnerable to natural events such as fires, earthquakes, or floods due to their small population size and limited range.

Species characteristics

SONCC Chinook are similar in appearance to Chinook from other basins in California, but are generally more rounded in shape and heavier. The Smith River regularly produces the largest Chinook salmon in the state, up to 36 kg (about 84 lbs.), though most average 10 kg (22 lbs.).

SONCC Chinook abundance has varied widely over time. The lower Klamath river tributaries likely supported a few thousand spawning adults each year. On the Smith River, historical run sizes are not known, but current numbers likely represent only a fraction of what they once were. Recent abundance estimates for SONCC Chinook in the Smith River are between 15,000 and 20,000 returning adults per year and the population is assumed to be stable.

SONCC Chinook generally migrate upstream to natal rivers in fall months (September- December) in the Klamath River and late-fall (November-December) in the Smith River to spawn. Depending on season and location, the majority of Chinook returning to spawn are three years old, though in some years four year old fish are the most abundant. Spawning typically peaks in December. Chinook use larger cobbles to build their redds than other salmon species. After 40-60 days, eggs hatch and fry emerge about a month later. Juvenile SONCC Chinook often spend at least a few months in fresh water feeding and growing before undertaking taxing ocean migrations. They emerge from the lower Klamath tributaries starting in February and migrate downstream through July on their journey to the sea.

SONCC Chinook salmon from the Smith River and lower Klamath River tributaries share genetic similarities. Lower Klamath River Chinook are genetically distinct from those in Klamath River tributaries upstream of the Trinity River confluence. In Blue Creek, there is a discrete late fall-run of Chinook, which seems to be segregated from other fish but requires more study. Very small numbers of spring-run Chinook salmon return to the Smith River in most years, but the relationship between these fish and the fall-run SONCC Chinook is not well understood at this time.

Conservation Actions

Conservation Strategy

  • Create volitional passage to spawning habitat in Battle Creek.
  • Increase juvenile survival by restoring floodplain habitats along lower Battle Creek, the mainstem Sacramento River, and the Yolo and Sutter bypasses.
  • The proposed trap and haul programs to truck both adult and juvenile winter run Chinook around Keswick, Shasta, and McCloud dams should be viewed as a last resort extinction prevention effort which should only be implemented after all other restoration measures have been exhausted.

Where to find Southern Oregon/Northern California Coastal Chinook Salmon

Southern Oregon/Northern California Coastal Chinook range from the Elk River, Oregon to the Klamath River’s confluence with the Trinity River. The majority of SONCC Chinook are found in Oregon streams. In California, they are found in the Smith River, Wilson Creek, and a few tributaries of the lower Klamath River such as Blue Creek. Unlike other Chinook salmon in California, SONCC Chinook tend to migrate and feed at sea north of Cape Blanco, Oregon.

How This Species Scored

From Caltrout’s SOS II Report

METRICSCOREJUSTIFICATION
Area occupied4Blue Creek and Smith River are the principal populations, along with smaller populations in tributaries.
Estimated adult abundance3Between 5,000 and 50,000 spawners in the Smith in most years; in 2011-2012, adult spawners were estimated at 20,000. 1,500 spawners in Klamath tributaries in most years.
Intervention dependence4California populations are largely self-sustaining but some supplementation by hatcheries is likely.
Environmental tolerance3Multiple juvenile life histories and spawner age diversity demonstrate physiological tolerances.
Genetic risk3Limited hatchery operations in California, but some concern for hybridization with hatchery ‘strays’ from Rowdy Creek Fish Hatchery and other ESUs.
Climate change2Fall-run is least vulnerable to climate change as they spawn later and scouring of redds is less likely to influence juveniles; sea level rise may negatively affect rearing in estuaries; Smith River likely to retain runs under worst-case scenarios through end of the century. Vulnerable to increasing temperatures, changes in flow regimes in tributaries, and variable ocean conditions.
Anthropogenic threats3Multiple threats rated as “Medium.”
Average3.1LEVEL OF CONCERN: MODERATE
Certainty: 2. Least studied of Klamath River Chinook runs.

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