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Life Cycle of a Rainbow Trout (Spawning to Adult)

The life cycle of a rainbow trout has six stages. These are spawning, eggs, Alevins, parr, juvenile and Adult. These stages are almost similar for all types of trout.

Rainbow trout is very familiar to the trout lovers and trout fishermen. Here we will know how a rainbow trout grows before we find it on our table. The life cycle of a rainbow trout is similar to the life cycle of a brown trout. Every step of the rainbow trout’s lifecycle discussed below.


Trout’s nests are known as redds. The trout usually built their nest in the river gravel and lay their eggs there. The nest where the trout lay their eggs needs much oxygen. Otherwise, eggs won’t hatch properly. So, the female trout start building the nest in November and completes building the nest within January. In November-January, water remains cold and brings the necessary oxygen to the nest. The female trout searches for such gravel where the good flow of water is available. This ensures that the gravel is free from slits. The female trout checks many gravels and if finds a good one, she digs a hole there flexing the body.

The female trout release eggs in the nest called redd and then an adult male trout comes and release sperms to fertilize the eggs. Once the male trout releases sperms over the eggs, the female trout will seal the hole with the gravel.

Egg hatching

Hatching the eggs of trout can take 60 days to 97 days based on the temperature of the eggs. The percentage of successful hatching rate also depends on the condition of the water, water flows etc. if the water condition is good, more than 80% eggs can hatch but if the condition is not good it can be as low as 4% of the eggs. Eggs with a central line and black eyes are considered as healthy eggs.


The journey of trout begins from here, alvein is the name of newly hatched trout. Alveins slowly grows and gets the characteristics of an adult trout. Alveins remains closer to the gravels until it grows up.

Trout Fry

This is an important stage of the trout life cycles. In this stage alveins become fry and they start coming out of the gravel. A fry is tiny in size so there is a chance that the flowing water will move that away. So, shallow water is needed for them. In this stage, they start searching for tiny insects to eat. Though they are very small in size at this stage, they need much energy and so need many foods. The mortality rate of trout in this stage is extremely high and the adults try to keep the fry away from the neighbors.

Trout Parr

After successfully passing the dangerous fry stage, it’s time for a trout to become parr. A trout with age not more than 1 year is considered as per. They bear the distinctive sign that is called parr mark. But as they become adult, the mark disappears. Though they can now cope with the water flow, still they need to be guarded against fish-eating birds and other predators. In this stage, the trout like to find their territory in the downstream. A trout parr and a salmon parr are difficult to distinguish.


A trout that is adult but not able to spawn yet is called juvenile. Trout between age 1 and 2 are considered as a juvenile.

Adult Trout

Trout that remains after passing all the previous stages are the adult trout. They are responsible for protecting their territories in the river. Adult trout defend the territory from neighbors and take part in reproduction.

Before being the trout we catch and eat, every rainbow trout must pass these six stages of the life cycle. The adult male trout defend the young all the time and the adult female trout takes the responsibility of building a nest and look after the eggs.

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