Atlantic SalmonSalmo salarWhere and when to see them

The Atlantic salmon is a migratory fish native to rivers draining into the North Atlantic and to the ocean itself. Most populations begin life in freshwater, grow at sea and return to rivers to reproduce. Once abundant in the Rhine basin, salmon disappeared from the river system during the twentieth century following pollution, river engineering and the construction of migration barriers. Improved water quality, stocking and fish-passage projects have enabled salmon to return to parts of the basin. Recovery remains incomplete, and returning fish still face substantial obstacles.

Size

Adults typically 50–100 cm long; exceptionally up to about 150 cm.

Weight

Adults commonly 2–10 kg; exceptionally over 30 kg.

Lifespan

Usually 4–10 years, sometimes longer.

Status

Near Threatened globally (IUCN).

Young salmon spend their early years in freshwater, defending feeding positions in flowing water. Before migrating downstream, they undergo a transformation called smoltification that prepares them for life in seawater. At sea, they travel widely in search of food and grow rapidly. Adults generally return to their natal river system, using several navigational cues, including their sense of smell. Upstream migration depends on river flow, temperature and access past obstacles. During spawning, a female excavates a gravel nest, called a redd, where eggs are fertilized and then covered. Unlike Pacific salmon species that die after spawning, Atlantic salmon can survive and reproduce again, although many do not.

• Young salmon preparing to enter the sea are called smolts.
• Their sense of smell helps them recognize their home river.
• Some adults survive spawning and return to the sea.
• Salmon restoration is a flagship effort in the Rhine basin.

Wildlife opportunities depend on the river reach, water levels and species. River-specific viewing months have not been confirmed; general species seasons are not a local sighting forecast.

Atlantic salmon use both freshwater and marine habitats during their life cycle. Eggs develop in clean, oxygenated gravel, while juveniles occupy flowing river sections with suitable cover and feeding areas. Adults at sea inhabit the North Atlantic before returning through estuaries to freshwater. In the Rhine basin, the main river serves primarily as a migration corridor to spawning and nursery habitats in accessible tributaries. Dams, warm water, pollution and sediment-clogged spawning gravel can all reduce habitat suitability.

Juveniles feed mainly on aquatic insect larvae and other small invertebrates, also taking insects that fall onto the water. At sea, salmon eat small fish, crustaceans and squid. Their prey changes with location, season and body size. Returning adults generally stop feeding in freshwater and rely on stored energy during migration and spawning.

Common name

Atlantic Salmon

Scientific name

Salmo salar

Animal group

Fish

Size

Adults typically 50–100 cm long; exceptionally up to about 150 cm.

Weight

Adults commonly 2–10 kg; exceptionally over 30 kg.

Lifespan

Usually 4–10 years, sometimes longer.

Status

Near Threatened globally (IUCN).

Identification

Sea-run adults are streamlined and silvery, with a darker back and small dark spots concentrated mainly above the lateral line. They have a small fleshy adipose fin between the dorsal fin and tail. Compared with sea trout, salmon usually have a slimmer tail base and a more noticeably forked tail, although these features vary with age and condition. Spawning adults darken, males may develop a hooked lower jaw, and juveniles show dark vertical markings called parr marks.