Identification & Biology: Rainbow trout are unusual in that there are two forms which sometimes share the same habitat. The anadromous form called “Steelhead” migrate to the ocean, though they must return to fresh water to reproduce.
Steelheads also tend to be more silvery than the freshwater Rainbow form. Lake and stream dwellers tend to be lighter as well. River dwelling Rainbow Trout are generally darker and more brilliant. In all habitats, Rainbow’s backs varies from blue or green to a yellow-green or brown. They always have dark spots on their heads, backs, bellies and across their dorsal fins and cadula fins, a famed attribute of true trout. (Rainbow Trout are considered to be the best example of true trout know at this time) Rainbows also have a red or pink streak that runs from the gill cover to the caudal fin, inspiring their name. Steelhead usually lack the pink stripe and have chrome-colored sides.
Unlike other Pacific Salmon, Rainbow Trout and Steelhead do not necessarily die after spawning (they may spawn as many as four times). All Pacific Salmon, including male Steelhead, undergo changes when spawning or migrating to spawn. They change color, head and mouth shape. Steelhead populations and rainbow trout populations can and do interbreed at different levels. It is possible for the offspring of rainbow trout to become anadromous and for the offspring of steelhead to develop a resident life history.
Rainbows range from 12 to 36 inches in length. Steelhead grow longer, ranging from 50 to 122 cm (20 to 48 inches) in length. Steelhead range in weight from 2.5 kg to 10 kg (5.5 – 22 pounds).
The freshwater form is called “Rainbow Trout”, based on the broad red band along their sides. Steelhead are exactly the same species as Rainbow Trout. However, the difference is anadromy. After going to sea, their color changes, including loss of the red band. They stay at sea for 1-4 years, and return to fresh water to spawn. Rainbows stay in fresh water their whole lives.
Range & Habitat: The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America as well as much of the central, western, eastern, and especially the northern portions of the United States. The ocean going (anadromous) form (including those returning for spawning) are known as steelhead, or ocean trout (Australia).
Market Description: Rainbow trout and Steelhead are popular in western cuisine and are both wild caught and farmed for food. It has tender flesh and a mild, somewhat nutty flavor. However, farmed trout and those taken from certain lakes have a pronounced earthy flavor which many people find unappealing; many shoppers therefore make it a point to ascertain the source of the fish before buying. Steelhead are farmed, primarily in British Columbia and in Chile. Steelheads’ meat is pink like that of a salmon, and is more flavorful than the light-colored meat of a Rainbow Trout.