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The rainbow trout (Oncorhynchus mykiss)
=Interesting Creature=
By: Shervin Belgrave
Kaieteur News – The rainbow trout (Oncorhynchus mykiss) is a species of salmonid that is native to tributaries of the Pacific Ocean in Asia and North America as well as much of the central, western, eastern, and especially the northern portions of the United States.
The Rainbow Trout
The species has been introduced for food or sport to at least 45 countries, in every continent except Antarctica. In some of these locations, such as Southern Europe, Australia and South America, they have had very serious negative impacts on upland native fish species, either by eating them, outcompeting them, transmitting contagious diseases, or hybridization with closely related species and subspecies that are native to western North America. The maximum recorded life-span for a rainbow trout is approximate 11 years. This fish species is often sold as a replacement because they taste similar.
And since the rainbow trout is highly desired as both food and sportfish, a number of angling methods are commonly employed. In fact, they are a popular target for fly fishers. Spinners, spoons, and small crankbaits can also be used productively, either casting or trolling. They can also be caught on live bait; night crawlers, trout worms, and minnows are popular and effective choices.
They are farmed in many countries throughout the world. Since the 1950’s, commercial production has grown exponentially, particularly in Europe and recently in Chile. Worldwide, in 2007, 604,695 tonnes of farmed salmon trout were harvested with a value of US$2.589 billion dollars. The largest producer is Chile.
In Chile and Norway, the ocean cage production of this creature has expanded to supply export markets. Inland production of rainbow trout to supply domestic markets has increased strongly in countries such as Italy, France, Germany, Denmark and Spain. Other significant producing countries include the USA, Iran, Germany and the UK.
The rainbow trout has declined due to a number of human and natural causes. The U.S. National Marine Fisheries Service has a detailed description of threats. Some have been affected by habitat loss due to dams, confinement of streams in concrete channels, water pollution, groundwater pumping, urban heat island effects, and other byproducts of urbanization.
The rainbow trout is susceptible to enteric redmouth disease. There has been considerable research conducted on redmouth disease, as its implications for rainbow trout farmers are significant. The disease does not affect humans. So the trout and subspecies thereof, are currently EPA approved indicator species for acute fresh water aquatic toxicity testing.
It is known for its popularity and quality as a cuisine thus it is caught wild and farmed for as food. With tender flesh and a mild, somewhat nutty flavour, the rainbow trout is a delicacy. However, farmed trout and those taken from certain lakes have a pronounced earthy flavour which many people find unappealing; many shoppers therefore make it a point to ascertain the source of the fish before buying.
However, the rainbow trout is yet a predator with a varied diet and will eat nearly anything it can grab, in contrast to the legendary, selective image people often have of the fish’s dietary habits. Rainbows are not quite as piscivorous or aggressive as the brown trout or lake trout.
When young, insects make up a large portion of the diet, smaller fish (up to 1/3 of their length), along with crayfish and other crustaceans make up the remainder. As they grow, though, the proportion of fish increases in most all populations. Some lake dwelling lines may become planktonic feeders. While in flowing waters populated with salmon, trout will eat salmon eggs, alvein, fry, smolt and even salmon carcasses.
It is said that the sperm of rainbow trout contains protamine as does that of salmon and some other species of similar fish. Protamine sulphate is an “antidote” to the anticoagulant heparin. Originally protamine was isolated from fish sperm, but is now produced in the laboratory.
(Source: Wikipedia – The Free Online Encyclopedia)
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