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NATURAL HISTORY

CENTRAL CALIFORNIA COAST STEELHEAD TROUT } Oncorhynchus mykiss
FAMILY: Salmonidae

DESCRIPTION: Steelhead can reach up to 35 pounds in weight, though average size on the central California coast is generally smaller. Steelhead are usually dark olive in color, shading to silvery white on the underside with a heavily speckled body and a pink-to-red stripe running along their sides.

HABITAT: Steelhead require cold-water streams with adequate dissolved oxygen. Spawning habitat consists of gravel substrates free of excessive silt.

RANGE: The central California coast steelhead population inhabits coastal streams from the Russian River in Sonoma County south to Soquel Creek in Santa Cruz County, and tributaries of San Francisco and San Pablo bays.

MIGRATION: Adult steelhead migrate from the ocean into freshwater streams to spawn between December and March, and juveniles migrate downstream to the Bay or ocean in late winter and spring.

BREEDING: Female steelhead dig a nest (or redd) in a stream area with suitable gravel composition, water depth, and velocity. Male fish battle for the right to spawn with females. Females may deposit eggs in four to five nests within a single redd.

LIFE CYCLE: Steelhead eggs hatch in three to four weeks. Juvenile steelhead typically spend one to two years rearing in freshwater before migrating to estuarine areas as smolts and then into the ocean to feed and mature. Steelhead can then remain at sea for up to three years before returning to fresh water to spawn.

FEEDING: Young trout fry feed mostly on zooplankton. Adult steelhead eat aquatic and terrestrial insects, mollusks, crustaceans, fish eggs, minnows, and other small fishes.

THREATS: Threats include habitat destruction and modification from dams, water diversions, urban development, livestock grazing, gravel mining, logging, and agriculture.

POPULATION TREND: An estimated 94,000 steelhead spawned in streams of the central California coast in the early 1960s. Steelhead numbers in the Russian and San Lorenzo Rivers, which support the largest runs in the area, have declined seven-fold since then. Most coastal streams in the region have remnant runs of 500 fish or fewer. Of the 58 watersheds tributary to the San Francisco Bay estuary, only 24 still support steelhead and/or resident rainbow trout.

 

California steelhead trout photo courtesy Flickr Creative Commons/sgrace