Rainbow Trout ‒ Life cycle

Life cycle of trout has, like in other fishes, several interesting features. It starts in upper parts of rivers where males and females meet for breeding and eggs become fertilised. Mating may take place gregariously and in suitable areas one male can mate with more females. In our latitudes mating season includes Autumn and Winter and males improve their mating grounds by quickly flipping their fins. After laying and quick fertilization of eggs parents do not care about them in any other way. It is interesting that embryonal development continues even after hetching from an egg. Newly hatched trouts called allevins are feeding from their large yolk sac hanging from their bellies. Yolk sac is gradually getting smaller as it is digested by the trout and only after it is used up small fish starts getting food from their environment (it is called fry now). Europian as well as North American trouts create as adults several forms that look different from each other. Apart from the form of fast-flowing fresh streams there is another living in lakes and yet another form that lives in oceans and migrate to rivers only to reproduce.