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Atlantic Salmon

Atlantic Salmon: The Legendary King of the Fly-Fishing River

The Atlantic Salmon (Salmo salar) is a cold-water fish native to rivers flowing into the North Atlantic Ocean. Famous for its long migrations, powerful swimming ability and complex life cycle, it is one of the most recognizable salmon species in the world.

Unlike Pacific salmon, Atlantic Salmon can survive spawning and return to the ocean, giving some individuals the opportunity to reproduce more than once during their lives. They belong to the salmon family, Salmonidae, and the genus Salmo, making them close relatives of Brown Trout.

In Canada, wild populations occur primarily in eastern and northern regions. Ontario also considers Atlantic Salmon native and has reintroduced them to Lake Ontario after their historical disappearance from that system.

Identification

Adults have a streamlined, silvery body designed for long-distance swimming.

Their back generally appears blue-green, grey or dark olive, while the sides become bright silver and the belly remains pale.

Common identifying characteristics include:

Ontario notes that Atlantic Salmon have few large black spots on the gill cover and no spots on the tail, two useful features when separating them from similar salmonids.

Juveniles look quite different from ocean-going adults. Young fish develop dark vertical markings known as parr marks, often with red spots between them.

Where Are They Found?

The natural distribution spans both sides of the North Atlantic.

In North America, wild populations are concentrated primarily in eastern Canada, including:

The species also occurs across Greenland, Iceland, northern Europe and parts of western Russia.

Historically, Atlantic Salmon occurred in Lake Ontario. Ontario now lists the species as reintroduced to Lake Ontario, with occasional fish also occurring in the upper Great Lakes, some tributaries and Trout Lake near North Bay.

Preferred Habitat

Atlantic Salmon require different habitats during different stages of life.

Juveniles depend on cold, clean freshwater streams with suitable gravel, riffles, pools and reliable oxygen levels.

Important freshwater habitat can include:

Sea-run adults also depend on productive coastal and marine environments after leaving freshwater.

Connected migration routes are especially important because fish must move between spawning streams, juvenile habitat, estuaries and the ocean.

Dams, poor fish passage, degraded spawning gravel and warming water can interfere with that life cycle.

The Atlantic Salmon Life Cycle

The life cycle passes through several distinct stages.

Females deposit eggs in gravel nests called redds during fall. The eggs remain beneath the gravel through winter before hatching in spring.

Newly hatched fish are called alevins. They remain in the gravel while absorbing nutrients from an attached yolk sac.

After emerging, they become fry and begin feeding independently.

As juveniles grow, dark vertical parr marks appear along their sides. At this stage they are known as parr.

Parr can remain in freshwater for several years. DFO reports a freshwater residence of approximately 1 to 6 years, depending on water temperature and food availability.

Eventually, the young fish undergo smoltification, a physiological transformation that prepares them for saltwater.

The resulting smolts become more silver and migrate downstream toward the ocean.

After spending one or more years feeding at sea, mature adults return to freshwater to reproduce.

What Do They Eat?

Diet changes significantly throughout the life cycle.

Young river-dwelling salmon commonly consume aquatic insects and small invertebrates.

Their freshwater diet can include:

Once at sea, individuals shift toward larger prey and can feed heavily on small marine fish and crustaceans.

Marine prey can include herring, capelin, sand eels and other schooling fish.

Returning adults often reduce or stop feeding once they enter freshwater on spawning migrations. DFO notes that returning adults rely heavily on stored energy reserves while moving upriver.

Size and Growth

Size varies considerably among populations and life-history types.

Ontario lists fish approximately 25 to 70 centimetres (10 to 28 inches) long in provincial waters.

Sea-run adults can grow considerably larger because they gain access to abundant marine food.

Fish that spend multiple years at sea before returning generally attain larger sizes than one-sea-winter salmon.

A salmon returning after one year at sea is commonly called a grilse, while fish returning after two or more years at sea are known as multi-sea-winter salmon.

Growth depends on food availability, water temperature, time spent at sea and individual population characteristics.

Lifespan

Atlantic Salmon can live for several years and may complete more than one spawning migration.

Their lifespan varies among populations because juveniles can spend very different amounts of time in freshwater before entering the ocean.

Some parr remain in rivers for only a year or two, while others spend as many as six years in freshwater before becoming smolts.

After entering the ocean, adults may spend one or several additional years feeding before returning to spawn.

Individuals that survive spawning can add further years to their lives by returning to the ocean and potentially reproducing again.

Spawning and Reproduction

Spawning generally occurs during fall in cold freshwater rivers and streams.

Females select suitable gravel habitat and use their tails to excavate nests called redds.

Eggs are deposited in the gravel and fertilized by males. The female then covers the eggs with additional gravel.

DFO reports that females may produce approximately 1,500 eggs for each kilogram of body weight.

The eggs remain protected beneath the gravel throughout winter.

Spring warming eventually triggers hatching, beginning the next generation’s freshwater stage.

Do Atlantic Salmon Die After Spawning?

Not necessarily.

This is one of the biggest biological differences between Atlantic Salmon and Pacific salmon.

Pacific salmon such as Chinook, Coho, Pink, Sockeye and Chum generally die after reproduction.

Atlantic Salmon can survive.

Fish that survive spawning and begin returning toward the sea are known as kelts. After recovering and feeding in marine waters, some can return to freshwater and spawn again.

Repeated spawning isn’t guaranteed, but the ability to reproduce more than once is an important feature of the species.

Sea-Run vs. Landlocked Atlantic Salmon

Not every Atlantic Salmon migrates to the ocean.

Sea-run populations are anadromous. They hatch in freshwater, migrate to the ocean to feed and later return to rivers to reproduce.

Landlocked populations complete their entire life cycle within freshwater.

Both forms belong to the same species, Salmo salar.

Landlocked populations generally use large lakes as the feeding environment that would otherwise be provided by the ocean.

This life-history flexibility helps explain why the species can occur in both coastal river systems and some inland lakes.

Atlantic Salmon in Ontario

Ontario has a unique history with this species.

Atlantic Salmon were historically native to Lake Ontario but disappeared from the lake by the late 1800s.

The province has since undertaken restoration efforts aimed at re-establishing populations in the Lake Ontario ecosystem.

Ontario’s current species profile lists Atlantic Salmon as reintroduced to Lake Ontario and notes occasional occurrences in the upper Great Lakes, some tributaries and Trout Lake near North Bay.

This makes Ontario populations different from the large natural sea-run runs associated with Atlantic Canada.

Atlantic Salmon vs. Chinook Salmon

Atlantic and Chinook Salmon belong to different genera.

Atlantic Salmon are Salmo salar.

Chinook Salmon are Oncorhynchus tshawytscha.

One useful visual difference involves the mouth. Atlantic Salmon typically have a pale mouth and gums, while Chinook have a dark mouth and black gum line.

Tail spotting also differs. Atlantic Salmon generally lack spots across the tail, while Chinook usually show numerous dark spots.

Their life cycles provide another major difference. Atlantic Salmon can survive spawning, while Chinook normally die afterward.

This section would be a good internal-link location for your Chinook Salmon species page.

Atlantic Salmon vs. Coho Salmon

Coho Salmon also belong to the Pacific genus Oncorhynchus.

Both species can appear bright silver while feeding in open water, but tail and mouth characteristics help separate them.

Atlantic Salmon generally have little or no tail spotting.

Coho typically show dark spots on the upper portion of the tail and have different mouth pigmentation.

Their reproductive biology also differs. Coho die after spawning, while some Atlantic Salmon survive and return to sea.

Atlantic Salmon vs. Brown Trout

Atlantic Salmon and Brown Trout are especially closely related because both belong to the genus Salmo.

Their appearance can overlap, especially when young.

Brown Trout commonly display more obvious black and red spotting across their bodies, while adult Atlantic Salmon generally have a cleaner silver appearance with fewer large dark spots.

Atlantic Salmon also develop a strongly migratory life cycle in sea-run populations.

Because we’ve already rebuilt your Brown Trout species page, I’d link Brown Trout directly from this section.

Conservation

Conservation is particularly important for this species.

Wild Canadian populations don’t all share the same conservation status. COSEWIC evaluates Atlantic Salmon as multiple designatable units, meaning individual populations can face very different levels of risk.

Threats can include:

Some Canadian populations face severe conservation concerns.

The Inner Bay of Fundy population, for example, is federally protected and has experienced extremely large historical declines.

Fisheries and Oceans Canada now operates the National Atlantic Salmon Strategy 2024–2036, which focuses on restoration, science, policy and long-term stewardship.

Fishing for Atlantic Salmon

Atlantic Salmon have an enormous recreational fishing tradition, particularly in eastern Canada.

Fly fishing is strongly associated with the species, especially on rivers in Quebec, New Brunswick and Newfoundland and Labrador.

Anglers commonly use wet flies, streamers, traditional salmon flies and surface patterns.

However, recreational opportunities can change quickly because conservation requirements vary by population and river.

DFO currently notes that many recreational Atlantic Salmon fisheries in Atlantic Canada and Quebec are closed because of conservation concerns.

Anyone planning to fish for them should check the current regulations for the exact province, river and season rather than relying on general advice.

Interesting Facts

The scientific name is Salmo salar.

The species belongs to the same genus as Brown Trout.

Atlantic Salmon can migrate thousands of kilometres between freshwater and marine feeding areas.

Juveniles change from parr into smolts before entering saltwater.

Young fish can spend 1 to 6 years in freshwater before beginning their ocean migration.

Returning adults can survive spawning.

Post-spawning survivors are called kelts.

One-sea-winter adults are commonly called grilse.

Females can produce approximately 1,500 eggs for every kilogram of body weight.

Atlantic Salmon are native to Ontario and have been reintroduced to Lake Ontario.

Canada manages multiple genetically and geographically distinct populations rather than treating every Atlantic Salmon population as biologically identical.

Frequently Asked Questions

Where do Atlantic Salmon live?

Wild populations occur around the North Atlantic, including eastern Canada, Greenland, Iceland and northern Europe. Ontario has also reintroduced the species to Lake Ontario.

Are Atlantic Salmon native to Ontario?

Yes. They were historically native to Lake Ontario and have since been reintroduced after disappearing from the lake.

Do they live in saltwater or freshwater?

Both. Sea-run fish begin life in freshwater, migrate to the ocean and later return to freshwater to spawn. Landlocked populations remain in freshwater throughout their lives.

What do they eat?

Juveniles consume aquatic insects, larvae and small invertebrates. Ocean-going adults feed much more heavily on fish and marine organisms.

What is a parr?

A parr is a juvenile salmon living in freshwater. Parr display dark vertical bars along their sides that help provide camouflage.

What is a smolt?

A smolt is a juvenile that has undergone physiological changes allowing it to survive in saltwater. Smolts turn silvery and migrate downstream toward the ocean.

What is a grilse?

A grilse is an Atlantic Salmon returning to freshwater after approximately one year at sea.

Do Atlantic Salmon die after spawning?

Not always. Some survive, return to the ocean as kelts and may eventually reproduce again.

Are landlocked salmon a different species?

No. Landlocked Atlantic Salmon are still Salmo salar. They simply complete their life cycle entirely in freshwater rather than migrating to the ocean.

Are Atlantic Salmon endangered?

There isn’t one status that applies to every population. Canadian populations are assessed separately, and some face serious conservation concerns while others remain more abundant.