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Rainbow trout

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Rainbow trout
Scientific Classification
Binomial Name

Oncorhynchus mykiss

Rainbow trout zoomed in.jpg
Rainbow trout zoomed in

The rainbow trout is a species of trout known by the scientific name Oncorhynchus mykiss, which is also known as redband trout. [1] They are present throughout the world, and best known as a tasty meal and hard fighting game fish with a rainbow coloration. Their color changes throughout the year and reflects their habitat, age, sex and degree of maturity. Rainbow trouts are carnivores, mostly eating marine insects, and they may also eat crayfish, grasshopper, worms, and other fish. [2]

Body Design

Picture of rainbow trout's body color

External body

Rainbow trout have small, scale on their body. They usually lives in streams, rivers, or lakes. [3] Their fin colors are usually blue-green or yellow-green and have a pink stripe on the side of the body. Under abdomen, their colors are white or yellow, and have tiny black spots on their back and fins.[4] On the top of their bodies they have one dorsal fin and an adipose fin which makes the fish stable and smooth in the water. The tail is big enough to move which directs the fish while swimming. On the low side, they have pectoral fins. Even though it is small, they uses it to slow down. Larger pelvic fins are on the bottom to move up and down. Anal fins are in the lower bottom which are to help the fish steady in the water. [5] Rainbow trouts are usually about 20 to 30 inches (51 to 76 centimeters) long. The weight of the fish is around 8 pounds (3.6 kilograms). However, they can get up to 4 feet (1.2 meters) and weigh up to 53 pounds (24 kg).[6] The color of these fish can be changed by dieting and spawning. The fins create camouflage effect in the water because of protective slime that covers the scale, fish can live healthy.[7]

Internal body

The internal body design of the Rainbow trout is very similar to other trout's internal body design. They have a brain, neural spine, gills, heart, and swim bladder. The brain is for processing. The neural spine is to transmit signals to the body. The the gill for taking in oxygen from the water. The heart to pump blood. The swim bladder to help them float. Behind their eyes, Rainbow trout have earstones which are used for hearing and for keeping the fish balanced. Rainbow trout have several digestive organs that are covered by a bony ribcage. These digestive organs are the kidneys, liver, stomach, gall bladder, and anus. These fish usually consume a diet of insects, plankton, and small fish. Therefore, these digestive organs are specially developed for these diets. For example, there is an organ named pyloric ceca that helps the fish to digest and break down the hard foods like exoskeletal materials. Made up with two bones, these fish have an upper and lower jaw. The upper jaw helps the fish with flexibility when they are feeding. The lower jaw, which is lined with sharp and small teeth, it helps with catching the prey. Rainbow trout are famous for eating a lot of food. Also, their body design is very useful for hunting.[8]

Life Cycle

When the trout has grown up, it approaches to the sexual maturity. When the trout grows up to about 12-16 inches, it can spawn. This generally happens at the end of it's second year. During the end of the winter or the beginning of spring, when the temperature of the water rises, the adult rainbow trout looks for the shallow gravel or an appropriate clear water river. Breeding and spawning usually happens during late March to early July. It can be differed by the conditions of the winder or the place. Most of the rainbow trout lays egg in the streams, lakes, and rivers, where the water is stable and has gravel bottoms. Basically, spring or autumn is when rainbow trout spawns. Rainbow trout moves to the upper part of the stream to a spawning place in the early spring. After that, the female picks a right place like a gravel place or shallow. After she picks a place, she scoops out a shallow nest called a redd by turning her side and beating her tail up and down. The female prepares by putting herself in to spawn after the redd is ready. The male trout guards the female by shaking his body and swimming around her. The female goes to the bottom of the hole when she thinks that she is ready to lay. She starts to push her bottom stomach against the gravel. After she pushes her belly, about 200 to 8,000 eggs come out. They stay in the redd. Depending on water temperature, hatching usually takes about several weeks to four months. If a small fish attempts to come out from the gravel, it might take more than few weeks. The tiny trout gathers together as groups and take shelter along the stream. Their parents usually feed them by giving plant material, crustaceans, and other aquatic insects. Some parents give them their larvae. The young rainbow trout generally eats invertebrates because they can't eat the insects with bones. Rainbow trout live on the same environment for 2 or 3 years. After they have been living there for several years, they begin to move out into the larger and bigger ares such as oceans and lakes where rainbow trout can find various food.[9]


River where rainbow trout are found


Natural habitat of the Rainbow Trout is the cool, clear rivers, streams, and lakes. Rainbow trout have been introduced throughout the world. The eastern coast of Asia, the Pacific Ocean, and the Pacific Coast of Northern America are the places they came from. Nowadays, rainbow trout is distributed all over the United States except in some southern states, and in all the other continents. There are two different types of rainbow trout. One is Anadromous fish which are matured in the sea but goes to fresh water to produce. The second one is called steelhead trout, which is a sea going rainbow trout. They will leave their freshwater and follow a river to the sea. Then in the ocean, they will spend several years but later returns to the river of their birth to generate.[10][11]

Factors that affect rainbow trout

Rainbow trout is affected by pollution in many different ways. However, these affections are usually bad. Because of the pollution, there is a lot of loss of trout in many streams or rivers where they have been introduced. Trout receives suffering right from the poison and toxic such as chemical wastes that were thrown away into the rivers. A huge amount of aquatic life is killed by toxic wastes that were dumped without getting treated. This also causes the river to increase the temperature. This increase of temperature also affects the organisms that require certain temperature to sustain their lives. This pollution can also bother the levels of oxygen and it causes organisms to become sick or die if they cannot adapt these changes to their lives. Moreover, dams can affect rainbow trout. Rainbow trout has to migrate in order to maintain their live patterns. However, dams interrupt their live patters. Trout also are not used to different types of levels or water caused by dams. This can bring them to get confused when they are breeding, feeding, or spawning.Dams can always interrupt trout that are looking for food. Because of men's interruption to nature, less trout are found in rivers. They also have to raised in fish hatchery before they go into the rivers. These trout has to be fed with different types of food and adopt the life in a river later. There is another problem that trout always can compete each other for survival. In addition, there are some other things that affect the lives of trout; acid rain, chemicals, pesticide runoff, or mercury from nearby mines that enter the river after heavy rainfall. Surprisingly, rainbow trout are very significant for rivers to keep the ecosystem. Therefore, when they are interrupted by pollution, the streams and river can suffer with them. Trout also can be used food supply for humans. Therefore, if the number of trout decrease, it definitely affect the human life.[12]