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Steelhead
Facts
Overview
Steelhead trout, Oncorhynchus mykiss, belong to the family
Salmonidae, which includes all salmon, trout, and chars. Steelhead
are the anadromous (sea-going) form of rainbow trout, and are
native to Western North America and the Pacific Coast of Asia.
The anadromous steelhead is born in the upper reaches of freshwater
streams, remains there until it matures at 1-3 years, migrates
to the ocean as an adult, and then returns to the stream waters
to spawn. Steelhead do not die after they first spawn, and so
may return to the stream to spawn several times in their lives.
Steelhead can become quite large, reaching as long as 45 inches
in length and 40 pounds in weight. They look bluish from above,
tending to a greenish tint in fresh water. They have small black
spots on the dorsal area and fins.
Steelhead require a certain habitat to survive, and especially
important because they balance their lives between marine and
freshwater habitat. The marine environment encourages larger growth
than streams, and makes for more robust fish. The stream environment
is possibly the most important aspect of preservation of the steelhead
habitat because the fish require a certain habitat in a very small
space.
The ideal steelhead stream has a wide variety of pools and riffles,
the former creating hiding places with cool water and the latter
oxygenating the water. There must be a gravel streambed for the
fish to lay their eggs and for the eggs to receive fresh water
and oxygen throughout their development. Silt and sediment negatively
affect steelhead becuase they deprive eggs of oxygen and fill
in crevices where eggs "stick". The fish also require
woody debris for shade, resting and habitat.
Steelhead Trout is federally listed as a threatened species,
and the National Marine Fisheries Service is developing rules
to protect Steelhead Trout "critical habitat" on the Central California
Coast. Alameda County falls within the designated "critical habitat"
region, and we are developing plans to retain the remaining steelhead
in our waters and restore steelhead to the streams where it used
to swim freely.
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