Life Cycle of the Trout

There are four stages in a trout's life cycle:
egg, alevin, fry and adult.

Eggs
The whole process begins when the female trout lays clutches of eggs which are in turn fertilised by the male trout. Depending on the temperature of the water, after several weeks an embryo will begin to develop inside the egg.

Eyed Eggs
The developing trout embryo is black. Because it resembles an eye, at this stage of development it is referred to as 'eyed egg'.

Alevins
Around two weeks after the 'eyed eggs' shown themselves, the eggs hatch and tiny fish called 'alevins' emerge. Attached to the stomach of the alevin is a large yolk-sac which contains protein, sugars, minerals and vitamins, everything the little fish needs to survive until it begins to feed.

It takes several weeks for the alevin's mouth and eyes to fully develop and consume all of its yolk-sac. When the yolk-sac has been fully absorbed the little fish will shift from the bottom where they have been nestling, and start to swim freely.

Fry
At this stage when the trout begin to swim and are ready to start eating they are called 'fry'.The small fry will continue to consume food and grow as fast as it can.

Adults
The trout reaches full maturity at around two years. It is now able to reproduce and begin the cycle again.

British Trout Association, The Rural Centre, West Mains, Ingliston EH28 8NZ
Tel: 0131 472 4080    Fax: 0131 472 4083     E-mail: mail@britishtrout.co.uk