Steelhead trout (Oncorhynchus mykiss) is a species that is native to North America, west of the Rockies. Each population on the Pacific Coast is unique. Individuals develop differently depending on their environment. All O. mykiss hatch in the same surroundings. This includes a gravel-bottom stream, fast-moving water, and high amounts of oxygen. If they choose to remain in freshwater during their developmental months, they are called rainbow trout. If they migrate to the ocean, they are called steelhead trout. The marine environment causes the latter to become silver in color, develop a slimmer profile, and grow larger.

Photo by Ken Hammond, USDA (Public domain)

Habitat Loss & Dams Threaten Extinction

The California Central Coast (CCC) steelhead trout was federally listed under the Endangered Species Act in 1998, and then again, in 2006. Steelhead numbers approached 1-2 million annually in the 1800s, but today that number has declined dramatically. This population decline is due to a number of reasons, but most importantly, the increase of habitat loss and dam construction. It is estimated that 80% of historical steelhead spawning habitat is found above now-impassible dams.

There are two major populations of CCC steelhead trout. One is centered on the Russian River and the other is found within the San Francisco Bay watershed. These two populations have experienced a significant downward decline and are at a high risk of extinction due to habitat loss and the existence of dams. This is important because damming:

• Causes mortality of adult and juvenile fish.
  
  
• Irreparably alters fish communities.
  
  
• Diminishes stream quality.
  
  
• Causes migratory and spawning difficulties.
  
  
• Damages refugia for the fish.
  
  

Combatting the Brink of Extinction

Conservation efforts to combat declining populations include a number of tactics. The Federal Recovery Outline for CCC steelhead designated approximately 1,465 miles of stream and 386 miles of estuary as Critical Habitat in 2007. Both public and private organizations attempt to restore and improve stream habitat by maintaining adequate riparian buffers, limiting sediment buildup, and reducing pollutants. Most importantly, there is the deconstruction and removal of dams in Central California. Ensuring ecologically sustainable flows and reducing the human impact on the California landscape will ultimately help bring the Steelhead trout back from the brink of extinction.

Sources

Israel, Joshua. Moyle, Peter and Purdy, Sabra. “Salmon, Steelhead, and Trout in California: Status of an Emblematic Fauna.” Report commissioned by California Trout. Center for Watershed Sciences, University of California, Davis. 2008. Pp 1-316.

National Marine Fisheries Service Southwest Region-Santa Rosa Field Office. “The Effects of Summer Dams on Salmon and Steelhead in California Coastal Watersheds and Recommendations for Mitigating Their Impacts.” 23 July 2001. Pp. 1-47.

“Rainbow Trout or Steelhead.” National Wildlife Federation. NWF, 1996-2015. Web. 31 January 2015. http://www.nwf.org/wildlife/.../rainbow-trout-or-steelhead.aspx

"Steelhead Trout (Oncorhynchus Mykiss)." NOAA Fisheries. NOAA, 15 Jan. 2015. Web. 31 Jan. 2015. http://www.nmfs.noaa.gov/pr/species/fish/steelhead-trout.html#threats

U.S.A. California Department of Fish and Wildlife. Fisheries Branch. “A Comprehensive Monitoring Plan for Steelhead in the California Central Valley”. By Christopher D. Eilers, Jennifer Bergman, and Ryan Neilson: Department of Fish and Game, October 2010. Print.

USA. NOAA. National Marine Fisheries Service: Southwest Region. “North-Central California Coast Recovery Domain: 5 Year Review: Summary and Evaluation of Central California Coastal Steelhead DPS and Northern California Steelhead DPS.” NOAA. Pp. 1-67. http://www.nmfs.noaa.gov/pr/pdfs/species/ccc_nc_steelhead_5yearreview.pdf

“Whole Effluent Toxicity.” Water: Whole Effluent Toxicity. EPA. 18 June 2014. Web. 31 January 2015. http://water.epa.gov/scitech/methods/cwa/wet/index.cfm