About the Salmon

About the Salmon

Atlantic salmon (Salmo salar) are anadromous, that is they spend their adult lives in the sea and migrate to rivers to spawn where their offspring spend their juvenile life stages.

Salmon mainly enter our rivers between March and October and once they have entered the river they stop feeding and survive from the body mass derived from the rich feeding grounds in the sea. The salmon spawn (lay their eggs in gravel nests in the river bed called redds) between November and January and the eggs incubate under the gravel until early spring when they hatch with a yolk sac attached, known as alevins. When the yolk sac is absorbed they push out from the gravel and disperse into the stream and are called fry. Later in the year they are called parr distinguished by clear ‘parr’ markings down their flanks which are like thumb prints.

The salmon spend between one and four years in a river before they turn silver and are called smolts. In the Frome which is in the south of England, most salmon go to sea after only one year in the river because they grow quickly in the milder climate and warm spring fed waters. Further north salmon tend to be slower growing and spend longer in the river before migrating to sea. This silvering process takes place in late winter/early spring and these little fish swim downstream congregating in shoals and arriving in the estuaries in April and May where they then enter the sea.

The small fish follow the ocean currents swimming northwards towards the feeding grounds off the Faroe Islands and Greenland. Some salmon mature and return to the river of their birth to spawn after only one winter in the sea and are called grilse, weighing between 4lbs and 10lbs. However, some salmon will stay at sea for two winters and some for even three winters before returning to their natal river. These fish can be very large weighing between 14lbs and 30lbs.

Illustration Courtesy of the Atlantic Salmon Trust and Robin Ade