Rainbow trout

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Rainbow trout
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Salmoniformes Family: Salmonidae Genus: Oncorhynchus Species: O. mykiss
Binomial name
Oncorhynchus mykiss Walbaum, 1792
Subspecies
See text.

The rainbow trout (Oncorhynchus mykiss), aka redband trout, is a species of Pacific salmon (1989) native to tributaries of the Pacific Ocean in Asia and North America. Fish which have gone to sea (including those returning for spawning) are known as steelhead, or ocean trout (Australia). The species has been introduced for food or sport to at least 45 countries, and every continent except Antarctica. In some of these locations, such as Australia, they have had very serious negative impacts on upland native fish species.

The species was originally named by Johann Julius Walbaum in 1792. In 1855, W. P. Gibbons found a population and named it Salmo iridia, however this name became deprecated once it was determined that this was a population of the already named species.

[edit] Physical characteristics

Uniform spots on the tail fin are characteristic of Oncorhynchus mykiss

Rainbow trout are unusual in that although they can spend their entire life in fresh water, they are capable of migrating to sea water when conditions are right, though they must return to fresh water to breed.

The freshwater form is called "rainbow trout" or "redband trout", based on the broad red band along their sides. After going to sea, their color changes, including loss of the red band, and they are called "steelhead".

They occur in cool streams up to 4,500 m in elevation.

Rainbows and steelhead have small black spots along their back, dorsal fin and caudal fin. Behind the dorsal fin, rainbows have an adipose fin that is commonly clipped from fish raised in a hatchery. Clipping the adipose fin helps distinguish hatchery fish from wild fish when they are taken by anglers. This allows enforcement of regulations to protect wild rainbows. Rainbows have a red or pink streak that runs from the gill cover to the caudal fin, inspiring their name. The color of a rainbow's back varies from blue or green to a yellow-green or brown. Steelhead usually lack the pink stripe and have chrome-colored sides. Rainbows are distinguished from their cousins, the cutthroat trout (Oncorhynchus clarki) by their short maxilla, which reaches to, but not past the rear margin of the eye. Rainbow trout also lack hyoid teeth, a feature present in cutthroat trout.

Rainbows range from 30 to 45 cm (12 to 18 inches) in length. Steelheads grow longer, ranging from 50 to 100 cm (20 to 40 inches) in length. Steelhead range in weight from 2.5 kg to 10 kg.

[edit] Lifecycle

Like salmon, steelhead are anadromous: they return to their original hatching ground to spawn. Different populations of steelheads migrate upriver at different times of the year. "Summer-run steelhead" migrate between May and October, before their reproductive organs are fully mature. They mature in freshwater before spawning in the spring. "Winter-run steelhead" mature fully in the ocean before migrating, between November and April, and spawn shortly after returning. Similar to Atlantic salmon, but unlike their Pacific Oncorhynchus kin, steelhead are iteroparous and may make several spawning trips between fresh and salt water.

[edit] As food

Rainbow trout is popular in Western cuisine and is often farmed for food. It has tender flesh and a mild, somewhat nutty flavor. However, farmed trout and those taken from certain lakes have a pronounced muddy flavor which many people find unappealing; many shoppers therefore make it a point to ascertain the source of the fish before buying.

[edit] Subspecies

A few populations are recognized as subspecies:

• California golden trout, Oncorhynchus aguabonita aguabonita (Jordan, 1892).
• Columbia River redband trout, Oncorhynchus mykiss gairdnerii (Richardson, 1836).
• Kern golden trout, Oncorhynchus aguabonita gilberti (Jordan, 1894).
• Coastal rainbow trout, Oncorhynchus mykiss irideus (Gibbons, 1955).
• Kamchatkan rainbow trout, Oncorhynchus mykiss mykiss (Walbaum, 1792).
• Baja California rainbow trout, Nelson's trout, or San Pedro Martir trout, Oncorhynchus mykiss nelsoni (Evermann, 1908).
• Great Basin redband trout, Oncorhynchus mykiss newberrii (Girard 1859)
• Sacramento golden trout, Oncorhynchus aguabonita stonei (Jordan, 1894).
• Little Kern golden trout, Oncorhynchus aguabonita whitei (Evermann, 1906).

[edit] Also See

• Sport fishing
• Fly fishing
• Golden trout
• Fishing
• Trout worms

[edit] References

• "Oncorhynchus mykiss". FishBase. Ed. Ranier Froese and Daniel Pauly. February 2006 version. N.p.: FishBase, 2006.
• Oncorhynchus mykiss (TSN 161989). Integrated Taxonomic Information System. Accessed on 30 January 2006.

[edit] External links

• Rainbow trout page from the Alaska Department of Fish and Game
• Rainbow trout information from Northern State University
• Australian Aquaculture Portal