By: Katie Kobayashi

PhD Student, UC Santa Cruz Department of Ecology and Evolutionary Biology

Talk to a long-time resident of the San Lorenzo Valley, and they might recall the days when Santa Cruz winters brought rain, a raging river and swarms of coho salmon migrating home from the ocean. Coho, or ‘silver’ salmon, once thrived in the San Lorenzo River and other regional streams. Although they are now rare, their impact on the Santa Cruz Mountains remains strong.

In many ways, the life cycle of coho salmon has shaped the redwood ecosystems that we call home. Coho salmon—like all five of the Pacific salmon species—are anadromous fish, meaning they are born in freshwater, migrate to the ocean to feed and grow, and return to the river as adults to spawn (Quinn 2005). In a poetic end to their life history, adult fish spend the last of their energy swimming against the current and protecting their newly formed nests (redds) before their bodies surrender to the steam. Ultimately, their passing brings new life—their redds produce a new generation of salmon while their bodies provide nutrient-rich food and fertilizer for the streams and forest (Stokes 2014).

What has happened to these iconic creatures? Historically, the range for Coho Salmon stretched from Norton Sound, Alaska to our very own Monterey Bay (Quinn 2005). However, their distribution and abundance is under threat. Understanding the decline of our salmon populations is a complicated topic, but fisheries scientists have come to summarize the causes of decline as “The Four H’s” (e.g. Brown et al. 1994):

Harvest: many populations have been over-exploited by fishing and consumption
Habitat: freshwater spawning and rearing habitat has been drastically altered and degraded
Hatcheries: some wild populations have been compromised by poorly-managed production hatcheries
Hydropower: dams have formed barriers to migration and cut off important habitat

Coho salmon are listed as ‘endangered’ throughout the California Central Coast region, and are functionally extirpated from most watersheds south of San Francisco (Spence and Williams 2011, Williams et al. 2016). The last remaining stronghold for the region is Scott Creek—a small coastal watershed just north of Davenport, CA. Today, Scott Creek serves as home base for an extensive recovery effort supported by a collaborative group of federal, state, university and NGO organizations (NMFS 2012). Scientists use a combination of genetic studies, conservation supplementation programs, tagging efforts and in-stream surveys to understand how the population changes over time (e.g., NMFS 2012, CDFW 2016). They then work with local leaders to carefully manage the population and ensure that their recovery can fuel a region-wide comeback.

Photo 1: Snorkeling in the upper San Lorenzo River in search of juvenile Coho Salmon as a laboratory assistant for NOAA Fisheries (Source: Personal Photo).

Through extensive habitat restoration and monitoring efforts, scientists and managers remain hopeful that coho salmon will return to the Santa Cruz mountains. The San Lorenzo River serves as a key site for the recovery of the coho salmon, along with nearby Soquel Creek and Aptos Creek (NMFS 2012, Williams et al. 2016). Each of these streams once provided ideal habitat for coho salmon comprised of cold, deep pools with wooded habitat for cover. As such, restoration projects such as large-woody-debris installations have been implemented across the region to support the re-colonization of coho salmon (e.g., TNC 2017, RCD 2017).


Photo 2: An adult coho salmon returning to the Santa Cruz Mountains to spawn (Source: NOAA Fisheries).

The future of coho salmon in the San Lorenzo River rests in the hands of our entire community. There are many things community members can do to support their recovery:

  • Stay informed: Attend local meetings like the State of the San Lorenzo River Symposium (March 17, 2018, 10am – 1pm, Zayante Fire House) to learn more about our river and how to protect it.
  • Keep it healthy: Do your part to keep the San Lorenzo River clean, cool, and flowing by reducing your waste, conserving water and avoid runoff from septic, fertilizers, and other chemicals.
  • Leave no trace: Whenever possible, avoid disturbing the natural state of the river. Undisturbed banks, shrubs, trees, logs and streambeds are crucial habitat components for spawning and rearing salmon.

With an entire community rallying behind them, there’s plenty of hope that coho salmon will return to the banks of the San Lorenzo River. In the last few weeks, Rosealea Bond, a NOAA team member with the life-cycle monitoring program, has reported seeing multiple wild returning adults to the region (Bond, personal interview). She has even detected tagged adult coho salmon swimming past monitoring stations she maintains on the San Lorenzo River (NMFS, Early Life History Team). Given these return events and detections, she remains “very optimistic for this year and next.”


Photo 3: Rosealea Bond, a laboratory assistant at NOAA Fisheries, collects data on a Coho Salmon at the Scott Creek life-cycle monitoring station. After taking measurements, she returns it to the river to continue its migration (Source: NOAA Fisheries).


Bond, R. (2018, March). Personal interview with K. Kobayashi.

Brown, L.R., P.B. Moyle, and R.M. Yoshiyama. (1994). Historical decline and current status of coho salmon in California. Department of Wildlife and Fisheries Biology, University of California, Davis.

CDFW. (2016). Fisheries Restoration Grant Program, publicly available information.

NMFS. (2018, March). Early Life History Team.

NMFS. (2012). Final Recovery Plan for Central California Coast Coho Salmon Evolutionarily Significant Unit. NMFS, Southwest Region, Santa Rosa, California.

Quinn, T. P. (2011). The Behavior and Ecology of Pacific Salmon and Trout. UBC Press.

RCD. (2017). 2017 Annual Report, Resource Conservation District of Santa Cruz County.

Spence. B.C. and T.H. Williams. (2011). Status Review update for Pacific Salmon and steelhead listed under the Endangered Species Act: Central California Coast Coho Salmon ESU. NOAA Technical Memorandum, National Marine Fisheries Service, Pg. 12.

Stokes, D. (2014). The Fish in the Forest: Salmon and the Web of Life. University of California Press.

TNC. (2017). California Salmon Snapshots.

Williams, T.H., B.C. Spence, D.A. Boughton, R.C. Johnson, L.G. Grozier, N.J. Mantua, M.R. O’Farrell, and S.T. Lindley. (2016). Viability assessment for Pacific Salmon and steelhead listed under the Endangered Species Act: Southwest. U.S. Department of Commerce, NOAA technical Memorandum NMFS-SWFSC-564.

Header Image by Joannatirn via Wikipedia, under Creative Commons

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