Editing Rainbow trout (section)

==Life cycle==
Rainbow trout, including steelhead forms, generally spawn in early to late spring (January to June in the Northern Hemisphere and September to November in the Southern Hemisphere) when water temperatures reach at least {{convert|42|to|44|F|C|order=flip|abbr=on}}.<ref name=Behnke2002-68/> The maximum recorded lifespan for a rainbow trout is 11&nbsp;years.<ref>{{cite web |url=http://www.fishbase.org/PopDyn/PopCharList.php?ID=239&GenusName=Oncorhynchus&SpeciesName=mykiss&fc=76 |title=List of Population Characteristics records for ''Oncorhynchus mykiss'' |publisher=Fishbase |access-date=2014-02-23}}</ref>

===Freshwater life cycle===
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 | image1    = Two pairs adult Steelhead trout and 2 redds March 2013 Stevens Creek.jpg
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 | alt1      = Photo of two pairs of spawning steelhead trout in stream
 | caption1  = Spawning steelhead
 
 | image2    = Rainbowtroutalevinandeggs.JPG
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 | alt2      = line drawing of alevin and eggs
 | caption2  = Eggs in gravel and rainbow trout [[Juvenile fish#Juvenile salmon|alevin]]

 | image3    = Oncorhynchus mykiss 02 by-dpc.jpg
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 | alt3      = Photo of juvenile rainbow trout
 | caption3  = Typical juvenile rainbow trout showing parr marks

 | image4    = Rainbow trout fish onchorhynchus mykiss detailed photography.jpg
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 | alt4      = Photo of adult rainbow trout
 | caption4  = Typical adult rainbow trout
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Freshwater resident rainbow trout usually inhabit and spawn in small to moderately large, well-oxygenated, shallow rivers with [[gravel]] bottoms. They are native to the [[River#Topographical classification|alluvial]] or freestone streams that are typical tributaries of the Pacific basin but introduced rainbow trout have established wild, self-sustaining populations in other river types such as [[bedrock]] and [[spring creek]]s. Lake-resident rainbow trout are usually found in moderately deep, cool lakes with adequate shallows and vegetation to support the production of sufficient food sources. Lake populations generally require access to gravelly-bottomed streams to be self-sustaining.<ref>{{cite web |url=http://www.dec.ny.gov/outdoor/60290.html |title=Steelhead Fishing in Lake Erie Tributaries |publisher=New York State Department of Environmental Conservation |access-date=2014-02-03}}</ref>

Spawning sites are usually a bed of fine gravel in a [[riffle]] above a pool. A female trout clears a [[Spawn (biology)#Brood hiders|redd]] in the gravel by turning on her side and beating her tail up and down. Female rainbow trout usually produce 2000 to 3000 {{convert|4|to(-)|5|mm|in|frac=32|adj=on}} eggs per kilogram of weight.<ref>{{cite journal |title=Mechanisms Controlling Egg Size and Number in Rainbow Trout ''Oncorhynchus mykiss'' |author1=Tyler, C.R |author2=Pottinger, T.G. |author3=Santos, E. |author4=Sumpter, J.P. |author5=Price, S-A |author6=Brooks, S. |author7=Nagler, J.J. |journal=Biology of Reproduction |volume=54 |year=1996 |pages=8–15 |issue=1 |doi=10.1095/biolreprod54.1.8 |pmid=8837994 |doi-access=free }}</ref> During spawning, the eggs fall into spaces between the gravel, and immediately the female begins digging at the upstream edge of the nest, covering the eggs with the displaced gravel. As eggs are released by the female, a male moves alongside and deposits milt (sperm) over the eggs to fertilize them. The eggs usually hatch in about four to seven weeks although the time of hatching varies greatly with region and habitat. Newly hatched trout are called sac fry or [[Juvenile fish#Juvenile salmon|alevin]]. In approximately two weeks, the [[yolk sac]] is completely consumed, and [[Fry (biology)|fry]] commence feeding mainly on [[zooplankton]]. The growth rate of rainbow trout varies with area, habitat, life history, and quality and quantity of food.<ref name=fwsRainbow>{{cite web |last=Staley|first=Kathryn|author2=Mueller, John |url=http://www.fws.gov/northeast/wssnfh/pdfs/rainbow1.pdf |title=Rainbow Trout (''Oncorhynchus mykiss'') |publisher=U.S. Department of Agriculture |date= May 2000|access-date=2013-12-16}}</ref> As fry grow, they begin to develop "parr" marks or dark vertical bars on their sides. In this juvenile stage, immature trout are often called "parr" because of the marks. These small juvenile trout are sometimes called 'fingerlings' because they are approximately the size of a human finger. In streams where rainbow trout are stocked for sport fishing, but no natural reproduction occurs, some of the stocked trout may survive and grow or "carryover" for several seasons before they are caught or perish.<ref>{{cite web |url=http://dnr.wi.gov/topic/fishing/trout/streamclassification.html |title=Wisconsin Trout Fishing: Trout Stream Classifications |date=2014-01-27 |publisher=Wisconsin Department of Natural Resources |access-date=2014-01-03}}</ref>

{{multiple image
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 | image1=Lake Erie Steelhead.jpg
 | alt1=Photo of Steelhead from Lake Erie
 | caption1=Steelhead from [[Lake Erie]]
 | image2 = Lake Washington Ship Canal Fish Ladder pamphlet - ocean phase Steelhead.jpg
 | alt2 = Drawing of ocean phase of male steelhead
 | caption2 = Male ocean-phase steelhead
 | image3 = Lake Washington Ship Canal Fish Ladder pamphlet - male freshwater phase Steelhead.jpg
 | alt3 = Drawing of freshwater spawning phase of male steelhead
 | caption3 = Male spawning-phase steelhead
}}<!--we now have the bottom two images in here twice, recommend keeping them in the chart, add the captions here to the chart, and deleting them at this location-->

===Steelhead life cycle===
{{see also|Salmon run|Steelhead}}
The oceangoing (anadromous) form, including those returning for spawning, are known as steelhead in Canada and the U.S.<ref>{{cite web|publisher=Alaska Department of Fish and Game|title=Steelhead/Rainbow Trout Species Profile|url=http://www.adfg.alaska.gov/index.cfm?adfg=steelhead.main|access-date=2013-08-26}}</ref> In [[Tasmania]] they are commercially propagated in [[Aquaculture of salmonids#Sea cages|sea cages]] and are known as '''ocean trout''', although they are the same species.<ref>{{cite web |url=http://www.mesa.edu.au/aquaculture/aquaculture14.asp |title=Mariculture in Tasmania Ocean Trout |publisher=Marine Education Association of Australasia |access-date=2014-02-23}}</ref>

Like salmon, steelhead return to their original hatching grounds to [[Spawn (biology)|spawn]]. Similar to Atlantic salmon, but unlike their Pacific ''Oncorhynchus'' salmonid kin, steelhead are [[Semelparity and iteroparity|iteroparous]] (able to spawn several times, each time separated by months) and make several spawning trips between fresh and salt water, although fewer than 10&nbsp;percent of native spawning adults survive from one spawning to another.<ref name=Behnke2002-70>{{cite book |last=Behnke |first=Robert J. |others=Tomelleri, Joseph R. (illustrator) |title=Trout and Salmon of North America |publisher=The Free Press|location=New York |isbn=978-0-7432-2220-4 |year=2002 |page=70 |chapter=Rainbow and Redband Trout }}</ref> The survival rate for introduced populations in the Great Lakes is as high as 70&nbsp;percent. As young steelhead transition from freshwater to saltwater, a process called "[[smoltification]]" occurs where the trout undergoes physiological changes to allow it to survive in seawater.<ref name="Nichols2008">{{cite journal |title=The Genetic Basis of Smoltification-Related Traits in ''Oncorhynchus mykiss'' |journal=Genetics |volume=179 |number=3 |date=July 2008 |author1=Nichols, Krista M. |author2=Edo, Alicia Felip |author3=Wheeler, Paul A. |author4=Thorgaard, Gary H. |pages=1559–1575 |doi=10.1534/genetics.107.084251 |pmc=2475755 |pmid=18562654}}</ref> There are genetic differences between freshwater and steelhead populations that may account for the smoltification in steelhead.<ref>{{Cite journal | last1=Hale | first1=MC | last2=Thrower | first2=FP | last3=Berntson | first3=EA | last4=Miller | first4=MR | last5=Nichols | first5=KM | title=Evaluating Adaptive Divergence Between Migratory and Nonmigratory Ecotypes of a Salmonid Fish, ''Oncorhynchus mykiss'' | journal=G3: Genes, Genomes, Genetics | volume=3 | issue=8 | pages=1273–1285 |date=August 2013 | doi=10.1534/g3.113.006817 | pmid=23797103 | pmc=3737167 }}</ref>

Juvenile steelhead may remain in the river for one to three years before smolting and migrating to sea. Individual steelhead populations leave the ocean and [[Fish migration|migrate]] into their freshwater spawning tributaries at different times of the year. Two general forms exist—"summer-run steelhead" and "winter-run steelhead". Summer-run fish leave the ocean between May and October before their reproductive organs are fully mature. They mature in freshwater while en route to spawning grounds where they spawn in the spring. Summer-run fish generally spawn in longer, more inland rivers such as the Columbia River. Winter-run fish are ready to spawn when they leave the ocean, typically between November and April, and spawn shortly after returning to fresh water. Winter-run fish generally spawn in shorter, coastal rivers typically found along the [[Olympic Peninsula]] and British Columbia coastline,<ref name=Behnke2002-68/> and summer-run fish are found in some shorter, coastal streams.<ref>{{cite web |url=http://wdfw.wa.gov/fishing/salmon/steelhead.html |title=Recreational Salmon Fishing Salmon/Steelhead Species Information Steelhead (Rainbow Trout) ''Oncorhynchus mykiss'' |publisher=Washington Department of Fish and Wildlife |access-date=2014-01-07 |archive-url=https://web.archive.org/web/20140107172404/http://wdfw.wa.gov/fishing/salmon/steelhead.html |archive-date=2014-01-07 |url-status=dead }}</ref> Once steelhead enter riverine systems and reach suitable spawning grounds, they spawn just like resident freshwater rainbow trout.<ref name=Behnke2002-68>{{cite book |last=Behnke |first=Robert J. |others=Tomelleri, Joseph R. (illustrator) |title=Trout and Salmon of North America |publisher=The Free Press|location=New York |isbn=978-0-7432-2220-4 |year=2002 |pages=68–72 |chapter=Rainbow and Redband Trout }}</ref>

=== Growth and oxidative stress on mitochondria ===
During periods of rapid growth and aging, trout display high levels of metabolic activity. High metabolic activity has been correlated with increased levels of oxidative stress <ref>{{Cite journal|last=Rollo|first=C.D.|date=2002|title=Growth negatively impacts the life span of mammals|journal=Evolution and Development|volume=4|issue=1|pages=55–61|doi=10.1046/j.1525-142x.2002.01053.x|pmid=11868658|s2cid=42123902}}</ref><ref>{{Cite journal|last=Alonso-Alvarez|first=C.|date=2007|title=Increased susceptibility to oxidative damage as a cost of accelerated somatic growth in zebrafinches|journal=Functional Ecology|volume=21|issue=5|pages=873–879|doi=10.1111/j.1365-2435.2007.01300.x|doi-access=free|bibcode=2007FuEco..21..873A }}</ref> and decreased machinery repair <ref>{{Cite journal|last=Almroth|first=B.C.|date=2010|title=Early-age changes in oxidative stress in brown trout, Salmo trutta|journal=Comparative Biochemistry and Physiology, Part B|volume=155|issue=4|pages=442–448|doi=10.1016/j.cbpb.2010.01.012|pmid=20117229}}</ref> in rainbow trout. During high oxidative stress, the [[Mitochondrion|mitochondria]] are the most important organelle contributing to tissue damage because of their role in metabolism and production of [[reactive oxygen species]]. In a study done by Almaida-Pagàn et al.,<ref>{{Cite journal|last=Almaida-Pagàn|first=P.|date=2012|title=Age-related changes in mitochondrial membrane composition of rainbow trout (Oncorhynchus mykiss) heart and brain|journal=Comparative Biochemistry and Physiology, Part B|volume=163|issue=1|pages=129–137|doi=10.1016/j.cbpb.2012.05.013|pmid=22634369|hdl=1893/8959|hdl-access=free}}</ref> researchers identified changes to the heart and brain mitochondrial membrane phospholipid composition in rainbow trout due to the differing levels of oxidative stress each organ faced during a high-stress time such as rapid growth and development. Stock rainbow trout of ages 1, 2, and 4 years had their heart and brain mitochondria isolated and analyzed for fatty acid composition. The tissues showed an overall similar percentage of total phospholipids but differed in the types and proportions of phospholipids. With age, the heart showed more unsaturated phospholipids, which are more susceptible to peroxidation, and thus, damage. The brain mitochondria of rainbow trout show decreased levels of [[docosahexaenoic acid]] and a lower peroxidation index, suggesting a lower susceptibility to damage by oxidative stress and a different reaction to growth compared to heart mitochondria. During the trout's development into an adult, a time of intense growth, the mitochondrial membrane composition and fluidity changes, which can cause defects in the [[electron transport chain]]. These defects combined with altered machinery repair and reactive oxygen species may cause more detrimental effects on the mitochondria in the fish as it matures. {{Clear}}