The coho salmon (Oncorhynchus kisutch), also known as the silver salmon, is native to California and ranges upwards along the Pacific Coast through Canada, Alaska, Russia, and Japan. These populous fish stocks were used as a common food source for the indigenous peoples of California and Catholic Missionaries in the 1800s. At the end of the Mission era, the mature forests and pure waters of Central California attracted settlers who were moving out West. With this influx of people, sawmills were built to harvest trees and the timber was used to build local cities, especially San Francisco.

(Photo, public domain)

With the increase in human population, coho salmon numbers decreased dramatically. Colonization of Central California in the 1800s destroyed local forests, caused sedimentation and silt to build up in streams, increased water temperatures and dams obstructed access to salmon spawning territory. These complex threats are still relevant today and have forced the coho salmon to near extinction. In 2007, research proved that coho populations had declined 99% from their levels in 1930. However, to combat these stressors, major legal and conservation efforts have taken place.

The coho salmon was first listed as Threatened under the Endangered Species Act in 1996 and then re-listed as Endangered in 2005 because of their near extirpation. In 1999, the Federal government designated critical habitat across their range along the Pacific Coast. Now, fast-forward to 2012, when the National Marine Fisheries Service published a recovery plan for coho salmon targeting watershed restoration and investment in hatchery practices.

One such hatchery is owned by the Monterey Bay Salmon and Trout Project, located at Kingfisher Flats in Santa Cruz County. This hatchery is responsible for raising 35,000 coho salmon that can be released into the wild with the goal of mitigating damage from dams and overfishing., though only about 2% of those salmon survive to reproduce. Some conservationists argue that when hatchery-bred fish interbreed with wild salmon, they produce offspring that are biologically inferior to their purely wild counterparts, making them more vulnerable to parasites and diseases.

To prevent further damage to coho populations, there has been an increase in restoration projects to improve local watersheds. For example, within the San Lorenzo and San Vicente Creek watersheds, 44 fish barriers have been removed and 22 miles of riparian habitat have been restored. And 10 miles of road have been decommissioned. These combined actions have prevented 38,000 cubic yards of sediment from entering local streams.

Current numbers of coho salmon are unclear, but scientific studies to quantify the existing populations are underway. As of 2009, it is estimated that there are less than 500 wild spawning adults within California. Ultimately, both legal and physical conservation efforts are pivotal in preventing the coho salmon from going extinct.

Image by Timothy Knepp, US Fish and Wildlife Service (Public domain) 

Sources

Anadromous Salmonids of the MBNMS: Coho Salmon. National Ocean Service. Monterey Bay National Marine Sanctuary. Reviewed 5 March 2014. Web. Accessed 14 February 2015. http://montereybay.noaa.gov/sitechar/fish2.html

Brown, Larry. R., Moyle, Peter. & Yoshiyama, Ronald. (1994). Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management. Volume 14(2): 237-261.

California Department of Fish and Wildlife. Web. Accessed 14 February 2015.
https://www.dfg.ca.gov/fish/Resources/Coho/SAL_CohoRange.asp

California Salmon Snapshots. 2014. Nature Conservancy. Web. Accessed 14 February 2015.
http://www.casalmon.org/salmon-snapshots/restoration/san-lorenzo-river

Coho Salmon (Oncorhynchus kisutch). NOAA Fisheries Office of Protected Resources. Updated May 15, 2014.Web. Accessed 14 February 2015. http://www.nmfs.noaa.gov/pr/species/fish/cohosalmon.htm

Overview of the CCC Coho Salmon ESU. Final CCC Coho Salmon ESU Recovery Plan. 2012. Volume I of III. Pp 48-85. Accessed 17 February 2015. Web. http://www.westcoast.fisheries.noaa.gov/.../central_california_coast_coho/overview_i.pdf

Pacific Salmonids: Major Threats and Impacts. NOAA Fisheries. Updated May 14, 2014. Web. Accessed 14 February 2015.
http://www.nmfs.noaa.gov/pr/species/fish/salmon.htm

Recovery Strategy for California Coho Salmon: Report to the California Fish and Game Commission. 2004. State of California. Resources Agency. Department of Fish and Game. 594 pp. Web. Accessed 14 February 2015. https://www.dfg.ca.gov/fish/.../ReportToCommission_2004/CohoRecoveryStrategy.pdf

Swimming with History: California Central Coast Coho Salmon. 2013. NOAA Fisheries. Web. Accessed 16 February 2015. http://www.nmfs.noaa.gov/pr/laws/esa/40th/cohosalmon.htm

The Problem With Hatcheries: Salmon Nation
http://www.salmonnation.com/essays/hatcheries.html