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Learn about salmonids

The life cycle of anadromous Atlantic salmon. Illustration by Robin Ade (published with permission from The Atlantic Salmon Trust)

Lifecycle - from eggs to adults

Salmonids are a family of ray-finned fishes, including species of salmon, trout and char, as well as whitefishes and graylings. SMOLTPRO is primarily concerned with anadromous (sea-migrating) populations of two salmonid species: Atlantic salmon (Salmo salar) and Brown trout (Salmo trutta). Although these salmonids spend most of their adult life in the sea, they all spawn in fresh water.

In Northern rivers and streams, spawning occurs in september to december, when females deposit eggs into excavated gravel nests. The eggs are then fertilised by competing males, and subsequently covered with gravel by the female, as a protection against predation and displacement.

In the following spring, the salmonid eggs hatch into alevins (sac fry), remaining in the river bed and feeding off the yolk-sac for several weeks. Having depleted this energy reserve, the fish emerge from the gravel to start searching for food as free-swimming fry. The small fraction of fry that survive a summer of intense predation and competition, increase dramatically in size and develop into parr.

In sea-migrating populations, parr that have grown for one to four years undergo a suite of behavioral, morphological and physiological changes to become smolt, which group together and head out to sea. As young adults, salmonids spend years in the ocean, increasing further in size before they return to their natal stream, re-adapt to fresh water conditions and spawn.


Learn more

Watch the life cycle of Pacific salmon (Oncorhynchus sp.) in larger format here.

This film (The Brown Trout and the Mayfly) can also be viewed in larger larger format here.

Page Manager: RASMUS KASPERSSON|Last update: 12/13/2010

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