Steelhead

william12340
 
Steelhead isn't salmon. Salmon Trout and Steelhead ar varieties of trout, a wholly completely different fish from identical family of fish as salmon. A salmon is usually a salmon, however a Steelhead starts its life out as a Rainbow Trout. If the Rainbow Trout migrates to the ocean, it becomes a Steelhead...

You may want to look at a recent book on Taxonomy.  Pacific Salmonids are Genus Onchorynchus.
Oncorhynchus tshawytscha   King or Chinook Salmon
Oncorhynchus kisutch   Coho Salmon
Oncorhynchus mykiss   Rainbow trout
 
There a number of distinct strains of mykiss, such as coastal Rainbow Trout, and Redband Trout, which occupy the same streams as Steelhead but stay resident in their natal streams.  In New York, DEC works with Washington strain fish (Chambers Creek) that were definitely anadromous, and a strain raised at the Randolph Hatchery, commonly referred to as Domestic Rainbows, that may trace back to the fish imported to Caledonia by Seth Green in the 1800's from the McCloud River in CA .  It is commonly accepted that the pattern of outmigration from natal stream into a large water body to feed and grow, and then return to the natal stream is enough to call a Rainbow trout a steelhead, whether it ever sees salt or not.
 
Atlantic Salmon, on the other hand are members of Genus Salmo, true trouts.
Salmo salar   Atlantic Salmon
Salmo trutta  Brown trout 
 
 
http://spsseg.org/meet-the-7-species-of-pacific-salmon/