Description[edit] edit
The freshwater form of the steelhead trout 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 rainbow trout do not leave freshwater. Steelhead are normally a steel blue color with silver running down the sides and under the belly, they also have black spots speckling their body covering the head, sides, back, dorsal fins, and caudial fins. As Steelhead return to freshwater they become more colored like a stream rainbow trout, with a pink stripe down the sides and an olive colored back.[1] Steelhead can weigh up to 55 pounds (26 kg) and reach 45 inches (114 cm) in length. Steelhead can live up to 11 years in proper condition.[2]
When the fish are newly hatched, they feed on zooplankton and small insects. Once mature, the fish eat a large variety of food sources: fish eggs, insects, crustaceans, mollusks, small fish, and terrestrial animals.[3]
Reproduction edit
During spawning, Female Steelhead will lay their eggs on gravel bottoms of freshwater tributaries, The preferred depth for the steelhead spawning is 6 in to 14 in[2] The female digs out a hole called a redd. She then lays the eggs in the hole, and a male fertilizes them.[4] Depending on the size of the female she may lay up to 9000 eggs. The females then buries the eggs in a foot of gravel. The eggs remain in the gravel until they hatch. Unlike Salmon who can only spawn once, Steelhead may return to the ocean, and come back up streams several times for spawning season.[5]
Threats edit
A number of distinct population segments of steelhead trout are endangered or threatened across the United States, This is becuse of humanization, such as agriculture, mining, forestry, and urbanization, all thought to block, limit, and degrade waterways for steelhead habitat.[1] During droughts or low water seasons recreation fishing causes a decrease in steelhead.[6]
Conservation edit
There have been several conservation programs created since the near extinction of the steelhead in the 1940s[5]. 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.[6]
Steelhead trout are endangered within the area of:[3]
- Southern California DPS
Steelhead trout are threatened within the areas of:[3]
- California Central Valley DPS
- Central California coast DPS
- Lower Columbia River DPS
- Middle Columbia River
- Northern California DPS
- Puget Sound DPS
- Snake River Basin DPS
- South-Central California coast DPS
- Upper Columbia River DPS
- Upper Willamette River DPS
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References edit
- ^ a b Thorp, James H.; Rogers, D. Christopher (2011), "Mussels and Clams", Field Guide to Freshwater Invertebrates of North America, Elsevier, pp. 83–95, ISBN 9780123814265, retrieved 2019-11-02
- ^ a b "Steelhead". www.calfish.org. Retrieved 2019-10-30.
- ^ a b c Fisheries, NOAA (2019-06-27). "Steelhead Trout | NOAA Fisheries". www.fisheries.noaa.gov. Retrieved 2019-11-11.
- ^ "For repeat-spawning steelhead, more than once is worth the risks". Life at OSU. 2018-04-12. Retrieved 2019-11-14.
- ^ a b "Rainbow Trout and Steelhead". National Wildlife Federation. Retrieved 2019-10-30.
- ^ a b "Steelhead - Sierra Forest Legacy". www.sierraforestlegacy.org. Retrieved 2019-11-11.