Salmo salar

Salmon can grow very large: up to 1.5 meters long. They eat herring, smelt and crustaceans. The first years of life is spent in fresh water, after which they migrate to sea. After 1 to 3 years at sea, they migrate back to their place of birth to spawn. There is little known about where they stay at sea. From marked specimen, it appears that a large number of salmon migrate to waters around Greenland, thousands of kilometers from their spawning grounds.

Until the early 19th century the life cycle of the Atlantic salmon was not understood and juvenile stages were thought to be different species. Females dig a depression in the gravel into which eggs and sperm are released simultaneously. The first juvenile stage (alevins) hatch and remain in the gravel, feeding on yolk sacs that are attached to the body. The next stage (fry) feed on microscopic particles in the stream. When vertical markings appear on the young fish's body the juveniles are known as parr. This stage remains in the river for two to six years before they transform into 'smolt'. A silvery colouration develops and complex internal changes occur to allow survival in salt water. Adult Atlantic salmon spend most of their lives at sea where they roam vast distances in small groups in search of food. At sea their diet consists of squid, shrimp and small fish such as herring or cod. After one or more years the salmon return to their birthplace in order to spawn, and do not eat during this phase of their life cycle. It appears that an olfactory sense (sense of smell) enables the salmon to identify their exact natal location and they are able to leap vertical distances of up to an amazing 12 feet in their endeavour to return there.

The Atlantic salmon, 'the leaper', has been called the king of fish, due primarily to their spectacular ability to clear seemingly insurmountable obstacles. Their large body is long and hydrodynamic and can measure up to 150 cm in length and weigh up to 39 kg. Adults are usually a silvery grey colour with some black spots but become more reddish with purple spots in the breeding season, and males develop a hooked lower jaw for fighting.

Amphihaline species, spending most of its life in freshwater (Ref. 51442). Some landlocked populations exist. Found in all rivers where temperature rises above 10° C for about 3 months per year and does not exceed 20° C for more than a few weeks in summer (Ref. 59043) (preferred temperatures 4-12°C). Juveniles may live in cold lakes in northern Europe (Ref. 59043). Parr (i.e. juveniles) are territorial and are found in the upper reaches of rivers and streams, in riffle areas with strong current and rough gravel bottoms (Ref. 7471). During winter, parr seek refuge in small spaces or under stones during the day (Refs. 59043, 89461). Young remain in freshwater for 1 to 6 years, then migrate to coastal marine waters or even to open oceans where they remain for 1 to 4 years before returning to freshwater for spawning (Ref. 51442). Adults inhabit cooler waters with strong to moderate flow (Ref. 44894). The Atlantic salmon is reported to live up to 10 years, but most individuals only reach 4-6 years (Ref. 88187). Juveniles feed mainly on aquatic insects, mollusks, crustaceans and fish; adults at sea feed on squids, shrimps, and fish (Ref. 51442). Most populations depend mostly or exclusively on stocking due to degradations of environmental conditions. Fishing pressure on wild stocks has decreased due to intensive farming but other problems have increased. Farmed salmons escape in large numbers and move to any river and hybridize with wild stocks (Ref. 59043). This species may hybridize with trout (Salmo trutta) (Ref. 59043). Diseases of the species include furunculosis (Aeromonas salmonicida), corynebacterial kidney disease (Renibacterium salmoninarum), enteric red mouth disease (Yersinia ruckeri), infectious pancreatic necrosis virus, bacterial kidney disease, fin rot and fungus infections (Ref. 5951). Marketed fresh, dried or salted, smoked, and frozen; eaten steamed, fried, broiled, cooked in microwave, and baked (Ref. 9988).

 Salmo salar can grow up to 150 cm in length and weights of 39 kg or more. The colour is dependant on habitat and age. When at sea, the dorsal area is silvery and blue-green, the sides silvery, the belly white and there are dark spots along the lateral line. In freshwater, the silvery colour is lost and the fish becomes a more mottled brown, the spots darken, become larger and are ringed by a paler colour. The number and size of spots and the depth of colour also varies with age and sexual maturity. Atlantic salmon have two dorsal fins, the second is situated near the tail and is small and fleshy with no fin rays. The tail fin is slightly forked.Due to a highly acute sense of smell, Salmo salar is able to remember the smell of the river in which it was born and on maturity return to these home grounds to spawn (Dipper, 2001). As a result of the numerous hazards, both natural and anthropogenic, most females do not make it back to the sea from their spawning grounds (Dipper, 2001). Salmo salar is a non-shoaling species (Whitehead et al. 1986) and may be confused with the similar looking brown trout (Salmo trutta), which is smaller and has much larger, more widely distributed spots.

Aquaculture of Salmo salar is big business and highly contentious. Production has increased dramatically since the 1960s and now dwarfs the wild salmon fisheries (WWF, 2001). Farming salmon to relieve pressure from wild stocks may seem like a good idea but it can have severe environmental consequences. In Britain, salmon farms are established in Scottish sea lochs and in estuaries. Salmon are cultivated in high concentrations, making them susceptible to parasites and disease. The proximity of these farms to wild populations, and the frequency with which cultivated salmon escape, puts the local wild populations at risk, both from the spread of disease and increased competition (Hendry & Cragg-Hine, 2003).

The Atlantic salmon is native to the basin of the North Atlantic Ocean, from the Arctic Circle to Portugal in the eastern Atlantic, from Iceland and southern Greenland, and from the Ungava region of northern Quebec south to the Conneticut River (Scott and Crossman, 1973).

Biogeographic Regions: nearctic (Native ); palearctic (Native ); atlantic ocean (Native )

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: North Atlantic, south to Portugal in the east, south to Connecticut and Housatonic rivers in the west (possibly formerly to Delaware); north to Ungava Bay (northern Quebec) and to the Nastapoka River in eastern Hudson Bay (Morin 1991); inland in North America to Lake Ontario, where now extirpated; widely stocked in lakes but seldom successfully. A spawning population, evidently derived from feral adults used for aquaculture, appears to be established in the Tsitika River in British Columbia, and freshwater and marine recoveries are well documented in Alaska (Volpe et al. 2000). Locally common, but depleted or extirpated from western and southern parts of range (Page and Burr 1991). The only remaining populations that are believed to consist, at least in part, of native fishes in U.S. rivers occur in Maine: Dennys, Machias, East Machias, Narraguagus, Pleasant, Ducktrap, and Sheepscot rivers (Colligan and Nickerson 1996); a few populations have been partially restored through hatchery production (Federal Register, 20 January 1994).

North Atlantic Ocean: temperate and arctic zones in northern hemisphere (Ref. 51442).In the western Atlantic, it ranges from western Greenland and the coastal drainages of Quebec, Canada, to Connecticut, USA (Ref. 5723). Landlocked stocks are present in North America (Ref. 1998). In the eastern Atlantic, it ranges from the White and Barents Sea basins through northeastern Europe to the Baltic and North Sea basins, including Iceland (Ref. 59043). Introduced to New Zealand, Chile, southern Argentina (Ref. 59043) and Australia (Ref. 6390).Listed in Appendix III of the Bern Convention (2002) (freshwater only).Listed in Annex II (freshwater only; excluding Finnish population) and V (freshwater only) of the EC Habitats Directive (2007).

Historic Range:

Western Atlantic, Eastern Atlantic, North Sea, Baltic Sea, Mediterranean Sea, North America and northern Europe; farmed elsewhere with escapees; also introduced elsewhere.

Coastal waters of the North Atlantic, In the Eastern Atlantic extends northward to the Arctic Circle, southward to the Mino River, at the boundary between Spain and northern Portugal.

Historically the Atlantic salmon could be found throughout the North Atlantic in a range spreading from Quebec to Connecticut in the west and from the Arctic Circle to Portugal in the east. In the last 30 years however, the salmon population has suffered a devastating decline with catches falling by more than 80 percent. Today many populations are teetering on the brink of extinction or have already been lost, and it is believed that Atlantic salmon numbers are only reasonably healthy in four countries; Norway, Ireland, Iceland and Scotland. Across the UK, populations in nearly 50 percent of salmon rivers are at risk and over 30 percent are endangered.

Sea-run Atlantic salmon usually attain a larger size than do landlocked (those living in entirely fresh water) salmon. Sea-run salmon range from 2.3 to 9.1 kg and commercially caught fish average 4.5 to 5.4 kg. The world record rod-caught Atlantic salmon weighed 35.89 kg and was caught in the Tana River of Norway.

The adult Atlantic salmon is a graceful fish, deepening rearward from a small pointed head to the deepest point under the dorsal fin, then tapering to a slender caudal peduncle which supports a spreading and slightly emarginate caudal fin. Atlantic salmon are distinguished from the Pacific salmon because they have fewer than 13 rays in the anal fin. Their mouth is moderately large. The shape, length of head, and depth of body vary with each stage of sexual maturity.

Color varies with age of this fish. Small "parr," older young salmon, have 8 to 11 pigmented bars, or "parr marks," along each side of their body, alternating with a single row of red spots along the lateral line. These markings are lost when the "smolt" age is reached. Salmon in the sea are silvery on the sides and belly, while the back varies with shades of brown, green, and blue. Atlantic salmon also have numerous black spots, usually "X"-shaped and scattered around the body. When spawning, both sexes take on an overall bronze-purple coloration and may acquire reddish spots on the head and body. After spawning, the "kelts" are so dark in color that these fish are also called "black salmon"

(Eddy and Underhill, 1974; Bigelow, 1963; Scott and Crossman, 1973).

Range mass: 2.3 to 35.89 kg.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Dorsal spines (total): 3 - 4; Dorsal soft rays (total): 9 - 15; Anal spines: 3 - 4; Analsoft rays: 7 - 11; Vertebrae: 58 - 61

Length: 140 cm

Maximum size: 1500 mm TL

150 cm TL (male/unsexed; (Ref. 7251)); 120 cm TL (female); max. published weight: 46.8 kg (Ref. 41037); max. reported age: 13 years (Ref. 274)

to 150 cm TL; max. weight: 174 kg.

Distinguished from congeners by having the following unique characters: 10-13 scales between end of adipose base and lateral line; 17-24 gill rakers (Ref. 59043); caudal fin deeply forked in individuals smaller than 20 cm SL; hyaline or grey adipose margin; posterior part of vomer toothless (Ref. 59043). Mouth extends only to area below rear of eye and has well developed teeth (Ref. 51442). Vomerine teeth weak (Ref. 7251). Caudal fin with 19 rays (Ref. 2196). Little scales (Ref. 51442). Juveniles have 8-12 blue-violet spots on the flanks with little red spots in-between (Ref. 51442). Adults at sea are bluish-green dorsally becoming silvery along the sides and white ventrally; with a few black spots but none under lateral line (Ref. 37032, Ref. 51442). Caudal fin usually unspotted and adipose fin not black bordered. During reproduction individuals lose the silvery shine and become dull brown or yellowish. Males may be mottled with red or have large black patches (Refs. 37032, 51442, 88171). Skin becomes thick and leathery. Survivors lose their spawning coloration and are generally dark in colour (Ref. 84357). During the spawning season, males are characterized by elongated hooked jaws that meet at the tips, thicker fins, and slime covering their body. Hook of males dwindle after spawning (Ref. 35388).

The Atlantic salmon is an anadromous species, living in fresh water for at least the first 2 or 3 years of life before migrating to sea. Relatively large cool rivers with extensive gravelly bottom headwaters are essential during their early life. Smolts migrate to sea where they may live for 1 or 2 years before returning to fresh water. The movements of Atlantic salmon at sea are not well understood. Tagging has shown that while some salmon wander, the great majority return to the river in which they were spawned. When at sea, salmon seem to prefer temperatures of 4 to 12 C. They may withstand exposure to temperatures in their lower lethal limit (-.7 C) and their upper lethal limit (27.8 C), but only for a short period of time (Bigelow, 1963).

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: rivers and streams; coastal

Habitat and Ecology

Systems

• Freshwater
• Marine

Habitat Type: Freshwater

Habitat Type: Freshwater

Comments: Rocky runs and pools of small to large rivers; lakes (Page and Burr 1991). Young remain in gravelly streams for 1-5 years (generally 1-2 years, but up to 8 years in some areas), then (as smolts) enter sea (or lake in landlocked populations) and remain there for 1-4 years. Migration habitat between spawning area and ocean optimally should have a minimum of slow- or no-flow areas. At sea, may remain within influence of estuary or move as far as Greenland. Prior to spawning, holds in streams through summer and early fall; optimum conditions include pools of 6 ft or more, water velocity below 1.6 ft/sec, and temperatures of 50-54 F (Clark et al. 1993).

Spawns in streams, usually in gravel-bottomed riffle above or below a pool. In Canada, streams with pH below 4.7 have no existing salmon runs; no impact was observed in streams with pH above 5.4 (Watt 1986, cited by Clark et al. 1993). Eggs are laid in a nest and covered with gravel. Normal egg development requires water temperatures less than 50 F (optimum 43 F). Rearing habitat includes shallow riffle areas interrupted by pools and deeper riffles. Parr require cover such as large rocks. Adults die or return to sea after spawning (males sometimes overwinter in stream). Usually spawns in natal stream.

benthopelagic; anadromous (Ref. 92381); freshwater; brackish; marine; depth range 0 - 210 m (Ref. 57178), usually 10 - 23 m

Depth range based on 160 specimens in 1 taxon.
Water temperature and chemistry ranges based on 33 samples.

Environmental ranges
  Depth range (m): 0 - 210
  Temperature range (°C): -0.404 - 9.505
  Nitrate (umol/L): 1.687 - 13.503
  Salinity (PPS): 8.500 - 34.117
  Oxygen (ml/l): 2.247 - 7.806
  Phosphate (umol/l): 0.354 - 1.719
  Silicate (umol/l): 3.300 - 48.967

Graphical representation

Depth range (m): 0 - 210

Temperature range (°C): -0.404 - 9.505

Nitrate (umol/L): 1.687 - 13.503

Salinity (PPS): 8.500 - 34.117

Oxygen (ml/l): 2.247 - 7.806

Phosphate (umol/l): 0.354 - 1.719

Silicate (umol/l): 3.300 - 48.967
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 The adult Atlantic salmon spends its a life at sea, returning to freshwater to spawn. The juveniles inhabitat freshwater areas, before migrating to the sea. Juveniles undergo smolting; morphological and physiological changes which allow them to adapt to life in sea-water.

Benthopelagic; freshwater; brackish; marine; depth to 10 m. Spend first 6 years in freshwater, then move to ocean existence.

Adult Atlantic salmon are found in the open ocean at depths between 2 to 10 metres. They return to freshwater to spawn in the streams in which they themselves were born, often only returning to pristine river systems. This makes them a useful indicator species of a river's quality.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Migrates up to thousands of kilometers between freshwater spawning habitat and marine nonspawning habitat. A number of native landlocked populations are known. Resident and anadromous populations may be sympatric in some areas. Returns to natal stream in spring. In New England, adults ascend rivers beginning in spring, with a peak in June and continuing into fall.

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.

Young Atlantic salmon in streams eat mainly the larvae of aquatic insects such as blackflies, stoneflies, caddisflies, and chironomids. Terrestrial insects may also be important, especially in late summer. When at sea, salmon eat a variety of marine organisms. Plankton such as euphausiids are important food for pre-grisle but amphipods and decapods are also consumed. Larger salmon eat a variety of fishes such as herring and alewives, smelts, capelin, small mackerel, sand lace, and small cod. Prior to spawning, salmon cease to feed; they do not eat after they re-enter fresh water to spawn, despite their apparent willingness to take an artificial fly (Bigelow, 1963).

Animal Foods: fish; insects; aquatic crustaceans; other marine invertebrates; zooplankton

Primary Diet: carnivore (Piscivore , Insectivore , Eats non-insect arthropods)

Juveniles feed mainly on aquatic insects and crustaceans. At sea the Atlantic salmon is pelagic, usually found feeding near the surface (Ref. 59043) preying on fish and crustaceans (Ref. 35387). May make long distance feeding migrations while at sea (e.g. individuals from European rivers may migrate to rich feeding grounds around the Faeroes Islands and in western Greenland (Ref. 58137)). Adults do not feed in freshwater during the spawning and post-spawning migrations (Refs. 30578, 51442, 59043). Preyed upon by American mergansers, kingfishers, harbor seals, grey seals, sharks, pollock and tuna.

Comments: Adults eat fishes and crustaceans (euphausiids, amphipods, decapods) in salt water, do not feed in fresh water. Young in streams eat mainly aquatic insect larvae and terrestrial insects (Scott and Crossman 1973), sometimes fish eggs.

Juveniles: mollusks, crustaceans, insects, and fish. Adults: squids, shrimps, and fish.

Salmo salar (Salmo salar fry (0.3-5 cm)) preys on:
Baetis
Micronecta poweri
Chimarrha marginata
Chironomidae
Bacillariophyceae
algae
protozoa
Leuctra
Ephemeroptera
Diptera
Entomostraca
Collembola
Helmidae

Based on studies in:
Wales, Dee River (River)

This list may not be complete but is based on published studies.

Epitheliocystis. Bacterial diseases

Enteric Redmouth Disease. Bacterial diseases

Edwardsiellosis. Bacterial diseases

10,000 to >1,000,000 individuals

Comments: As of 2000, the estimated annual number of spawners in eastern North America was about 350,000, down from 1.5 million 30 years ago (Anderson et al. 2000). As of the late 1980s, New England population included about 3000-7000 adults returning to 16 rivers; of these, 1500-2500 were believed to be of wild origin. Prior to European colonization, Maine spawning runs may have been 125,000-500,000 (Beland 1984, cited by Clark et al. 1993). See Clark et al. (1993) and USFWS (1995) for information on current status in Maine.

Salmon have a great sense of smell, hearing, and taste which helps them find food and sense danger. Salmon are also able to sense danger by feeling the waves on their body.

Atlantic salmon also use their senses to find and return to their home river. Through imprinting, young fry memorize details about their home streams, and they use this knowledge as adult spawners to find their way back. Scientists are not exactly sure how salmon complete this feat, but some theories are the salmon use the sun and stars as navigational guides, while others claim these fish have stored the taste of their home water in their brain. Most feel that salmon are guided home by the characteristic odor of the parent stream which is imprinted during the smolts' migration (Maynor, 1996).

Communication Channels: visual ; tactile ; chemical

Perception Channels: visual ; tactile ; chemical

Hatching of the eggs usually occurs in April but the young remain in the gravel until the yolk sac is absorbed and finally emerge in May or June of the year following egg deposition. The newly hatched salmon, called "alevins," remain in rapid water until they are about 65mm long. The fish are now called "parr," and their growth is slow. Parr are called "smolts" when they reach a length of 12 to 15 cm and are ready to go to sea. Salmon grow rapidly while at sea. Some may return to the river to spawn after one year at sea, as "grilse," or may spend 2 years at sea, as "2 sea-year salmon" (Bigelow, 1963; Scott and Crossman, 1973).

At the onset of sexual maturity this species is known to return from the ocean to the river where it was born, and even to its specific natal site (Refs. 7471, 51442). Lacustrine populations move to tributaries (Ref. 59043). Spawning migration into freshwater lasts from June to November. Spawns at 6-10°C (Ref. 89464) in gravel river areas far upstream with moderate to fast-flowing, well-oxygenated waters and a succession of riffles and pools (Refs. 6390, 59043). The female selects a site where the gravel is of the right size and of sufficient depth (0.1 to 0.3 m) (Refs. 7471, 51442) and water depth is around 0.5-3 m (Ref. 35387). The female digs a depression ("redd") by turning on her side and flexing her body up and down, without touching the stones (Ref. 36794). This species spawns in pairs. The male guards and defends the female against other males (Ref. 59043). A female releases between 8,000-25,000 eggs during a spawning season (Ref. 7471, 88187); 500 to 2000 per kg (Ref. 51442). Fertilized eggs sink into the redd and are covered with a layer of gravel (0.1-0.3 m) usually by the male (Refs. 7471, 59043). Females are also observed to cover the eggs. Individual spawning is completed in 2-3 days (Ref. 7471) after a female digging several redds and spawning with several males. Period of spawning lasts for 1-2 weeks. Most males die after spawning, while 10-40% of females may survive and return to the sea in autumn or overwinter in rivers, feed one summer, and migrate again. They may spawn in the year following the first reproduction or may remain at sea for 18 months before returning once more to the river. Of the returning females, about 0.3-6 % spawn a second time and very few spawn a third or fourth time. In short rivers with presumably less exhaustive upstream migration, up to 34% of returning individuals spawn a second time; some individuals may spawn for up to six seasons (Ref. 59043). Eggs hatch in spring, usually after 70-160 days (Ref. 59043). Upon hatching, alevins (i.e. newly-hatched young up to 1 month) are negatively phototactic and move deeper into the gravel (Refs. 58137, 59043). As their yolk sac is absorbed, the fry emerge from the bottom and move to shallow riffles just downstream of their redd (Ref. 59043). Mortality of young individuals during the first months may range from 14-61 % (Ref. 89465). Parr (i.e. juveniles) may remain in freshwater environments for 1-7 years (depending on temperature and feeding conditions) but most stay for 2-3 years. Parr undergo morphological and physiological changes called smoltification which prepares them for life in the sea. At the southern end of their range, many reach a length of 12-15 cm, transform into smolts and are ready for migration in spring of the first year after hatching (Refs. 7471, 51442). At the northern end of the range they may take 5-6 years to reach smolt stage (Ref. 36794). Smolts move towards estuaries, the continental shelf and eventually the open ocean (Ref. 89462). The Atlantic salmon matures between 3-7 years (Ref. 41851). After 1-4 years at sea, it migrates back to the upper reaches of its natal river to spawn (Refs. 59043, 89461). It has an acute sense of smell and it is suggested that it imprints a sequence of odours while inhabiting rivers and during its smolt run. It presumably reverses this sequence to return to its natal site (Ref. 89461). Several studies have shown that smolt runs are strongly correlated to increasing water temperature and water flow during spring (Ref. 89461).

Range lifespan
Status: wild: 3 (high) years.

Average lifespan
Status: captivity: 3.3 years.

Average lifespan
Status: wild: 5.0 years.

Average lifespan
Status: wild: 13.0 years.

Maximum longevity: 13 years (wild) Observations: Like in many other salmonid species, most animals die after spawning (Patnaik et al. 1994). While most animals return to spawn in rivers, however, there are alternative life histories: parr and jacks have a small body size and mature early, yet while jacks return early to spawn from the ocean, parr never migrate and can survive reproduction and breed again (Hutchings and Myers 1994). Unverified estimates suggest these animals may live up to 14 years (http://www.fishbase.org/).+p Interestingly, one study showed that animals infected with a Pearl mussel parasite live longer, have a lower cancer incidence, and avoid the typical "programmed death" that follows reproduction possibly because the parasite needs the salmon to live one more year to complete its life cycle (Ziuganov 2005).

Atlantic salmon spawn in October and November, the peak of spawning usually occurring in late October. As spawning time nears, males undergo conspicuous changes in head shape: the head elongates and a pronounced hook, or kype, develops on the tip of the lower jaw. The nesting site is chosen by the female, usually a gravel-bottom riffle above a pool. The female digs the nest, called the "redd," by flapping strongly with her caudal fin and peduncle while on her side; the redd is formed by her generated water currents. The female rests freely during redd preparation while the male continues to court her and drive away other males. When the redd is finished, the male aligns himself next to the female, the eggs and sperm are released, and the eggs are fertilized during the intermingling of the gametes. On average, a female deposits 700-800 eggs per pound of her body weight. The eggs are pale orange in color, large and spherical, and somewhat adhesive for a short time. The female then covers the eggs with gravel, using the same method used to create the redd. The eggs are buried in gravel at a depth of about 12.7 to 25.4 cm.

The female rests after spawning and then repeats the operation, creating a new redd, depositing more eggs, and resting again until spawning is complete. The male continues to court and drive off intruders. Complete spawning by individuals may take a week or more, by which time the spawners are exhausted. Some Atlantic salmon die after spawning but many survive to spawn a second time; a very few salmon spawn three or more times.

Spawning completed, the fish, now called "kelts," may drop downriver to a pool and rest for a few weeks, or they may return at once to the ocean. Some may also remain in the river over winter and return to sea in the spring.

Hatching of the eggs usually occurs in April but the young remain in the gravel until the yolk sac is absorbed and finally emerge in May or June of the year following egg deposition. The newly hatched salmon, called "alevins," remain in rapid water until they are about 65mm long. The fish are now called "parr," and their growth is slow. Parr are called "smolts" when they reach a length of 12 to 15 cm and are ready to go to sea. Salmon grow rapidly while at sea. Some may return to the river to spawn after one year at sea, as "grilse," or may spend 2 years at sea, as "2 sea-year salmon" (Bigelow, 1963; Scott and Crossman, 1973).

Breeding interval: Breed once yearly, few breed twice before dying

Breeding season: October and November

Range age at sexual or reproductive maturity (female): 1 to 2 years.

Range age at sexual or reproductive maturity (male): 1 to 2 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

There is no parental investment beyond spawning.

Parental Investment: pre-fertilization (Provisioning)

Spawns in fall (late October and early November in Maine). Eggs hatch in early spring. Young spend 1-3 years in stream rearing habitat, go to sea (in spring), return to spawn after 1-4 winters at sea (most from New England spend two years at sea). Adults may spawn in more than one year. In Europe, the majority of the smallest adults spawned annually, the largest biennially (Jonsson et al. (1991). Apparently, severe post-spawning mortality is normal in natural habitats, but survivorship generally is higher in artificially "reconditioned" kelts or in lake-locked populations (Stearley 1992).

Anadromous, returning to natal rivers. Gravelly area in current.. Females produce 8,000 - 26,000 eggs. Juvenile salmon (parr) spend most of their freshwater life in shallow riffles; At length of 12 to 15 cm, transform to smolt and migrate to sea. Speed of growth slower in northern part of range.

Genomic DNA is available from 14 specimens with morphological vouchers housed at British Antarctic Survey

Year Assessed

• Needs updating

Assessor/s

Reviewer/s

Contributor/s

Canada

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: TNR - Not Yet Ranked

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Large breeding range in streams draining into the North Atlantic; many populations in the U.S. have been extirpated or have declined, but there are many occurrences and large numbers elsewhere; principal threats are habitat loss/degradation and overharvest.

Current Listing Status Summary

Status: Endangered
Date Listed: 07/20/2009
Lead Region:   Northeast Region (Region 5) 
Where Listed: U.S.A., ME, Gulf of Maine Distinct Population Segment. The GOM DPS includes all anadromous Atlantic salmon whose freshwater range occurs in the watersheds from the Androscoggin River northward along the Maine coast to the Dennys River, and wherever these fish occur in the estuarine and marine environment. The following impassable falls delimit the upstream extent of the freshwater range: Rumford Falls in the town of Rumford on the Androscoggin River; Snow Falls in the town of West Paris on the Little Androscoggin River; Grand Falls in Township 3 Range 4 BKP WKR, on the Dead River in the Kennebec Basin; the un-named falls (impounded by Indian Pond Dam) immediately above the Kennebec River Gorge in the town of Indian Stream Township on the Kennebec River; Big Niagara Falls on Nesowadnehunk Stream in Township 3 Range 10 WELS in the Penobscot Basin; Grand Pitch on Webster Brook in Trout Brook Township in the Penobscot Basin; and Grand Falls on the Passadumkeag River in Grand Falls Township in the Penobscot Basin. The marine range of the GOM DPS extends from the Gulf of Maine, throughout the Northwest Atlantic Ocean, to the coast of Greenland. Included are all associated conservation hatchery populations used to supplement these natural populations; currently, such conservation hatchery populations are maintained at Green Lake National Fish Hatchery (GLNFH) and Craig Brook National Fish Hatchery (CBNFH). Excluded are landlocked salmon and those salmon raised in commercial hatcheries for aquaculture.

Population detail:

Population location: U.S.A., ME, Gulf of Maine Distinct Population Segment. The GOM DPS includes all anadromous Atlantic salmon whose freshwater range occurs in the watersheds from the Androscoggin River northward along the Maine coast to the Dennys River, and wherever these fish occur in the estuarine and marine environment. The following impassable falls delimit the upstream extent of the freshwater range: Rumford Falls in the town of Rumford on the Androscoggin River; Snow Falls in the town of West Paris on the Little Androscoggin River; Grand Falls in Township 3 Range 4 BKP WKR, on the Dead River in the Kennebec Basin; the un-named falls (impounded by Indian Pond Dam) immediately above the Kennebec River Gorge in the town of Indian Stream Township on the Kennebec River; Big Niagara Falls on Nesowadnehunk Stream in Township 3 Range 10 WELS in the Penobscot Basin; Grand Pitch on Webster Brook in Trout Brook Township in the Penobscot Basin; and Grand Falls on the Passadumkeag River in Grand Falls Township in the Penobscot Basin. The marine range of the GOM DPS extends from the Gulf of Maine, throughout the Northwest Atlantic Ocean, to the coast of Greenland. Included are all associated conservation hatchery populations used to supplement these natural populations; currently, such conservation hatchery populations are maintained at Green Lake National Fish Hatchery (GLNFH) and Craig Brook National Fish Hatchery (CBNFH). Excluded are landlocked salmon and those salmon raised in commercial hatcheries for aquaculture.
Listing status: E

For most current information and documents related to the conservation status and management of Salmo salar , see its USFWS Species Profile

Classified as Lower Risk/least concern (LR/lc) on the IUCN Red List and listed on Appendix III of the Berne Convention. Freshwater populations are listed on Annex II of the EC Habitats Directive and Schedule 3 of the Conservation Regulations (1994).

Comments: Native U.S. populations south of Maine are essentially extirpated due primarily to the effects of dams and water pollution; excessive harvest of adults by humans, stream acidification, sedimentation of spawning and holding habitat, and possibly changes in water temperature regimes contributed to the decline in some areas. Evidence from New England indicates that landlocked populations of Atlantic salmon may be negatively influenced as abundance of northern pike and/or Esox hybrids increases. In the U.S., some of these threats have been alleviated; water quality has improved in recent decades, and fish ladders have been constructed at many dams; reintroduction programs are in progress. Poor marine survival continues to result in reduced returns to U.S. rivers (USFWS 1995, Anderson et al. 2000); depletion of forage species by commercial fisheries and freshwater exposure of juveniles to an endocrine disrupter (leads to mortality in marine phase) are suggested possible causes. Escaped farmed salmon may pose a threat to native populations in coastal Maine rivers (USFWS 1995). See USFWS (1995), NMFS (Federal Register, 29 September 1995), Colligan and Nickerson (1996), and Anderson et al. (2000) for further information on threats to North American populations.

Lower Risk: least concern (LR/lc)

The Atlantic salmon has shown a steady decline over the last two centuries, seemingly related to increased industrial development throughout their traditional home range. The situation has become drastically worse since the 1970s and catches of wild salmon have fallen by 80 percent. River pollution caused by industrialisation can severely damage local populations as can the increased number of man-made obstacles such as dams, weirs or the alteration of watercourses, which makes migration impossible. Salmon has become an extremely popular dish in the western world and commercial farming can affect wild populations in a number of ways; escaped salmon may erode the gene pool through interbreeding, or farms may act as foci for the spread of parasites and diseases to wild stocks.

Management Requirements: See Mills and Piggins (1988) and Mills (1989). See Clark et al. (1993) for a summary of management efforts in Maine. See Kornfield et al. (1995) for management recommendations for Maine populations. See "Maine Atlantic Salmon Restoration and Management Plan 1995-2000." See "Atlantic Salmon Conservation Plan for Seven Maine Rivers."

Needs: See USFWS (1997) for an explanation of the decision to withdraw the proposed rule to list a distinct population segment in Maine as threatened. See "Review of the status of anadromous salmon (Salmo salar) under the U.S. Endangered Species Act, July, 1999," available from USFWS (Paul Nickerson, 413-253-8615, Hadley, Massachusetts).

The North Atlantic Salmon Conservation Organisation was established in 1983 under the Convention for the Conservation of Salmon in the North Atlantic. It is an international organisation that aims to conserve and promote the rational management of salmon stocks in the wild. The organisation includes all countries in which the Atlantic salmon is historically found and many different measures have been taken to reduce exploitation and protect the salmon. However, numbers of salmon are not recovering and further research is being carried out into why this is the case.

The Atlantic salmon is renowned among game fishermen and is a highly prized food fish. Because of the strong market demand, an active aquaculture industry, which involves cage-rearing, hatcheries, and some sea ranching, has been developed all over the world. The commercial yield of the Atlantic salmon is estimated to be in the millions of dollars with expected annual doubling in the future (Scott and Crossman, 1973).

fisheries: highly commercial; aquaculture: commercial; gamefish: yes; price category: very high; price reliability: reliable: based on ex-vessel price for this species

Species Impact: A non-native population apparently established in British Columbia raises concerns that Atlantic salmon could jeopardize native Pacific salmonids "through competition for resources and occupation of niches that are currently underutilized" (Volpe et al. 2000).