Steelhead

Steelhead are native to the Pacific basin. Their North American range extends from southern California through Oregon, Washington, British Columbia and Alaska. Wild populations also occur across the North Pacific in Russia, particularly on the Kamchatka Peninsula. Within that enormous range, individual river systems support their own runs, migration timings and life-history patterns.

A young steelhead may spend one to several years growing in its home river before undergoing the physiological changes needed to survive in saltwater. It then migrates through the estuary and into the Pacific, where access to richer feeding grounds allows it to grow far larger than most resident rainbow trout. Fish, squid and surface-dwelling marine prey form an important part of their ocean diet. After one or more years at sea, the fish returns to freshwater, often finding the same river system where it began life.

One of the most interesting things about steelhead is that resident and migratory rainbow trout can exist within the same population. Fish born in the same watershed may follow completely different paths. One may remain in freshwater and mature as a modest river trout, while another enters the ocean and returns weighing well into double figures. The migratory strategy carries greater risk, but the reward is faster growth and access to a much larger food supply.

Steelhead runs are usually grouped into summer and winter fish, although those names refer to when they enter freshwater rather than when they spawn. Summer-run steelhead return before they are fully mature, often entering rivers from spring through autumn. They may travel far inland and hold in deep pools for months before spawning the following spring. Winter-run fish return in a more advanced stage of maturity, generally entering between late autumn and spring and spawning relatively soon afterwards. Both forms usually spawn during the same broad spring period.

This difference shapes where the fish are found. Summer steelhead are often associated with long river systems and upper tributaries, where they must arrive early to complete difficult inland migrations. Winter fish are more common in shorter coastal rivers, although there are plenty of exceptions. In either case, they favour cool, clean and connected water, with juvenile habitat, safe migration routes and suitable gravel for spawning.

Unlike the five Pacific salmon species, steelhead do not necessarily die after spawning. Some survive, return downstream as kelts and migrate back to sea, where they recover before attempting another spawning run. Repeat spawners are not the majority in every population, but this ability gives steelhead a life history that is more flexible than that of most Pacific salmon.

Steelhead have also established major fisheries outside their native Pacific range. The Great Lakes support large runs of migratory rainbow trout that move from the lakes into tributaries to spawn. These fish never enter saltwater, so they are more accurately described as lake-run or adfluvial rainbow trout. Anglers still call them steelhead because their appearance, size and migratory behaviour closely resemble the ocean-going fish of the West Coast.