Steelhead
Steelhead, or occasionally steelhead trout, is the anadromous form of the coastal rainbow trout or Columbia River redband trout. Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and North America. Like other sea-run trout and salmon, steelhead spawn in freshwater, smolts migrate to the ocean to forage for several years and adults return to their natal streams to spawn. Steelhead are iteroparous, although their survival rate is approximately only 10–20%.Description
The freshwater form of the steelhead is the rainbow trout. The difference between these forms of the species is that steelhead migrate to the ocean and return to freshwater tributaries to spawn, whereas non-anadromous rainbow trout do not leave freshwater. Steelhead are also larger and less colorful than rainbow trout. Steelhead can weigh up to and reach in length. They can live up to 11 years and spawn multiple times. The body of the steelhead trout is silvery and streamlined with a rounder head. This silver color and round head is what gives the steelhead its name. There are black dots that are more concentrated on the back of the fish and become sparser closer to the lateral line of the fish. Steelhead also develop a pink horizontal stripe. 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. When a steelhead exits the river and returns to the ocean again, it regains its silvery appearance while in saltwater. The fish develop a larger and stronger tail relative to a normal rainbow trout to help aid in swimming in ocean currents and swimming up strong river currents.
A number of distinct population segments of steelhead are endangered or threatened across the United States, with their decline largely attributed to causes such as changing ocean conditions, overharvest, hatcheries, habitat destruction, and the blocking of waterways by the construction of dams. Human interaction has had considerable consequences on reducing the population of steelhead trout.Characteristics
Steelhead currently support or have historically supported fisheries across Northern California, and thus they hold "economic as well as cultural value". Contrary to popular belief, the California Steelhead is a coastal variation of the same species of fish as the Rainbow Trout, Oncorhynchus mykiss; "rainbow trout are the 'landlocked' version, and remain in freshwater throughout their life" . 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. In fact, "coastal rainbow trout is the most widely-distributed native trout form". Among other necessary biological utilities fulfilled by this species, Steelhead Trout "are also strong indicators of the condition of California's streams; large self-sustaining populations of native salmon and trout are found where streams are in reasonably good condition". 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.
The Steelhead is an ocean-going predatory fish with a typical lifespan of four to six years. 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. When these fish enter the open ocean, however, their diet typically consists of squid, crustaceans, and small fish including anchovies, herring, and sardines, though the capacity at which this dietary intake occurs is highly contingent upon the geographical region where Steelhead choose to migrate. "Rainbow trout and steelhead represent two divergent ecotypes that are genetically identical but separated by life history strategies" ; the unique biological diversity of the Steelhead Trout from that of the Rainbow Trout is determined through a capacity to migrate to the open ocean. 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".Homing behavior
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. By recording the concentrations of solutes and the chemical profile of a stream through the biological characteristic of a chemical indicator, steelhead "use the position of the sun and magnetic north to navigate towards spawning grounds " after they have fed in the open ocean for 1–4 whole years. Even after traveling hundreds of miles, this chemical imprint allows steelhead to identify their precise hatching grounds upon returning to freshwater. According to "A review of the characteristics, habitat requirements, and ecology of the Anadromous Steelhead Trout" by Fulton, "homing creates genetically different subpopulations that differ by basin, stream, and even location within a stream". According to a study conducted by Heath & Pollard, "significant genetic variation on the individual, tributary, and watershed level occur between Steelhead Trout populations" as a result of this chemical reliance for breeding practices. The author concludes that as a result of such biologically accurate homing characteristics, the Steelhead Trout is "uniquely adapted to its environment"; fish populations "are reasonably isolated from fish that spawn in different areas," and therefore "sub-populations may differ by the timing of runs, size of fish, and even behavior patterns". This also influences genetic relatedness between Steelhead Trout populations; interestingly, the author found that the genetic similarity of regional Steelhead trout populations "is correlated with distance".Spawning
During spawning, the fish will lay their eggs on gravel bottoms of freshwater tributaries. The female digs out a hole called a redd. The preferred depth for steelhead spawning is. She then lays the eggs, and a male fertilizes them. The females will then cover the eggs with the gravel. Depending on the size of the female she may lay up to 9,000 eggs. The female then buries the eggs in a foot of gravel. The eggs remain in the gravel until they hatch. Unlike salmon steelhead may return to the ocean, and come back upstream several times for spawning season.Atlantic Canada
Small numbers of steelhead are present in Atlantic Canada.Conservation status
There have been several conservation programs created since the near extinction of the steelhead in the 1940s. The reduction in population is mainly due to manmade obstructions within river systems. This is usually caused by dams blocking access, or humans changing the river landscape for recreation and access to water. It is estimated that only 500 steelhead trout return to the Southern California watersheds. However, in other areas of the United States, steelhead can be seen as pests because they are an invasive species to the environment.Southern California
While numbers are improving in areas of the Pacific Northwest where Steelhead Trout have typically thrived, the California Steelhead Trout is considered a threatened species, and according to Mark Capelli of the National Marine Fisheries Service, the Southern California steelhead are the most endangered of them all. According to California Trout, Steelhead Trout populations began to decline in the "late-1940s due mainly to man-made landscape modifications". As a result of damming for flood control, steelhead migration routes from the coast to upstream spawning grounds were increasingly blocked over time. 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. As a result of widespread habitat loss and fragmentation, Southern California Steelhead populations were officially labeled as an endangered species in 1997. In some areas, a recent sighting of the Steelhead Trout has not occurred in years, and biologists fear the worst. In 2002, the endangered species label was extended from the Malibu Creek down to the border of San Diego and Mexico.Northern California
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. As of 2016, 48,892 Steelhead Trout were reportedly caught. Such a population count suggests that this fascinating fish species continue to persevere in Northern California waters. However, to ensure the continued rehabilitation of steelhead populations in Northern California, a positive, directive plan of action for steelhead conservation must occur. According to NOAA, The State of California Fisheries Restoration Grant Program "invested over 250 million dollars and supported approximately 3,500 salmonid restoration projects". Investments in projects improving "fish passage, water quality, instream habitat restoration, watershed monitoring, and education and organizational support" all occupy conservation efforts to improve Northern California steelhead populations. According to NOAA, "the percentage of floodplain and in-channel habitat that would need to be restored to detect a 25% increase in salmon and steelhead production was 20%". As it stands, "more than 20% of floodplain and in-channel habitat has been restored due to FRGP". Though these initiatives spell hope for the prospects of Steelhead Trout population rehabilitation, habitat degradation continues to occur at an alarming rate.