Steelhead

Steelhead (Oncorhyncus mykiss)

Steelhead (O. mykiss) and Coastal rainbow trout (O. mykiss irideus) are essentially the same fish in terms of genetics, but steelhead display an alternate midlife strategy--they migrate to the ocean and back to fresh water again at least once during their life cycle, making them anadromous. This also allows them to grow larger than "resident" rainbow trout, who live their entire lives in fresh water. The ability to become anadromous is unique to coastal rainbows; other varieties of rainbow trout do not have this ability. Coastal rainbow trout have been observed to have 32 different type of life history strategies based on the amount of time they spend in fresh water and salt water, spawning timing and frequency, and other attributes. Here we will stick to describing Russian River steelhead trout, though it should be noted that there is variation between individual Russian River fish, as well.

Steelhead are likely the most iconic fish of the Russian River watershed. Historically, the Russian River had 20-65,000 steelhead returning annually; the third largest runs in California, after the Sacramento and the Klamath. The Russian River steelhead fishery was world renowned up till the 1960’s. Every accessible stream in the watershed supported steelhead at one time, but human impacts such as logging, dams, water diversions, and agricultural and urban development, have caused extreme habitat degradation over centuries and this once-robust fishery has dwindled. Efforts to increase steelhead in the Russian have been in place since 1870 and continue today with the Warm Springs and Lake Mendocino hatcheries' steelhead production program. Russian River steelhead belong to the Central Coastal California (CCC) distinct population segment (DPS).

Life History

Steelhead display a tremendous variety of life history, as compared to other salmonids. The following is believed to be the most commonly observed life history for Russian River steelhead, though patterns and timing of juvenile and adult behavior may vary based on weather, ocean conditions and individual preference.

Steelhead begin their lives as eggs under gravel, hatch as alevin and emerge as fry after they absorb their yolk sack. Steelhead spend 1-2 years in their natal streams, then migrate downstream toward the ocean. As steelhead begin to smolt (go through a series of physiological changes to prepare for entering salt water), they utilize the estuary for various periods of time as an important feeding ground before entering the ocean. Steelhead span a long distance across the Pacific Ocean, where they spend 1-3 years before returning to fresh water streams as adults to spawn. Steelhead generally return to the Russian River between December and May, with the peak of the run between January and April, though upstream migration timing depends on rainfall needed to generate sufficient flow for access to spawning tributaries. Adult steelhead spawn and generally return to the ocean, where they could remain or return to fresh water to spawn multiple times.

Range

Central California Coast steelhead range from the Russian River watershed south to Aptos Creek in Santa Cruz County.

Habitat

Cold, clean water (preferably with access to areas <20°C)
Diversity of instream habitats (riffles and deep pools)
Complex cover like large woody debris and deep undercuts to hide in
Abundance of spawning gravel with low amounts of silt
Low to moderate gradient streams without migration barriers, though steelhead have been witnessed jumping more than 5 feet to access upstream habitat
Intact estuary habitat

Identifying Characteristics

Juveniles

Round parr marks on side of body with excess spotting on back and dorsal fin
Spots on either side of pupil in eye and on head and gill plate
Adipose fin has a dark edge

Adults

Range from very silver with light coloration on back with dorsal spotting to having an olive colored back and a pink to red lateral band
Caudal fin is spotted on both lobes
White mouth, no black
Body appears torpedo shaped, usually 30-70cm in length

Fun Facts

Steelhead are iteroperous, meaning they reproduce more than once. Although only 10-20% of steelhead return to spawn more than once, steelhead have been observed spawning up to at least four times!
Steelhead can jump up to 11 feet and go from 0-25 mph in one second!

References and Recommended Readings