Steelhead
When steelhead return to freshwater to spawn, their color begins to more closely resemble that of a normal rainbow trout.
The longer a steelhead spends in freshwater, the darker their green body colorations and horizontal pink stripe become.
A number of distinct population segments of steelhead are endangered or threatened across the United States, mostly caused by the blocking of waterways by the construction of dams.
An ocean-going variety, the Steelhead, or Oncorhynchus mykiss irideus has developed unique adaptive characteristics that distinguish this fish from its common counterpart and have allowed a wider distribution of this species across the Pacific Northwest, including the coastal regions of California.
A chrome underside and olive-grey back reminiscent to that of a steel beam are attributed as the main defining physical characteristic for which the Steelhead is distinguished and earns its namesake.
Like the common rainbow trout, Steelhead predominantly feast on zooplankton when they are young and then transition to eating fish, some rodents, mollusks, and crustaceans.
Homing behavior is a unique adaptation of Steelhead Trout that allows the fish to migrate to and from freshwater and saltwater bodies on multiple occasions.
Through the process of imprinting, Steelhead Trout deposit a chemical indicator "that is specific to their natal stream" (NRC 1996).
[6][7] Perhaps the most interesting and perplexing characteristic of the Steelhead Trout is its homing behavior and the capacity of this species to accurately detect its primary spawning grounds despite venturing to the open ocean and returning to the same freshwater source on numerous occasions throughout their lives.
Even after traveling hundreds of miles, this chemical imprint allows steelhead to identify their precise hatching grounds upon returning to freshwater.
Similar to native populations of steelhead on the west coast, Great Lakes steelhead start in tributaries to larger bodies of water, in this case the Great Lakes, where they travel to, to grow to large proportions and reach sexual maturity before returning to the tributaries they started in.
[11] They share very similar characteristics to an ocean-run steelhead as far as their long, slender build and silvery coloration with spots running along their back that very rarely progress beyond their lateral line.
As the fish spend more time in the tributaries they darken in coloration while developing a bright red stripe down their midline.
[citation needed] Due to the steelhead's large size and powerful demeanor, they've become very attractive amongst the angler community in the Great Lakes area.
As a result of damming for flood control, steelhead migration routes from the coast to upstream spawning grounds were increasingly blocked over time (California Trout).
Furthermore, largely a result of continued urbanization and to satisfy the needs of human populations in the area, river flows became modified for recreational purposes and a substantial diversion of water occurred over time (California Trout).
In 2002, the endangered species label was extended from the Malibu Creek down to the border of San Diego and Mexico (California Trout).
A threatened species since 2000, the Northern California steelhead represents a beacon of hope for continued rehabilitation initiatives and growing population numbers in the area.
Such a population count suggests that this fascinating fish species continue to persevere in Northern California waters.
Though these initiatives spell hope for the prospects of Steelhead Trout population rehabilitation, habitat degradation continues to occur at an alarming rate.
[15] Primary threats to MCR steelhead populations include hydrosystem operations, habitat alteration, and effects of stray naturally spawning hatchery fish.
[14] MCR steelhead were first listed as threatened on March 25, 1999, following the construction of Round Butte Dam at the confluence of the Deschutes and Metolius rivers.
[14] In a 2016 an action plan implementation progress report stated the population is "maintained" showing no significant upward or downward trend in the yearly number of returning adults in an experimental small tributary to the Deschutes River.
"A Review of the Characteristics, Habitat Requirements, and Ecology of the Anadromous Steelhead Trout (Oncorhynchus Mykiss) in the Skeena Basin," June 15, 2004, 16.
