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Overview

Brief Summary

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.
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Biology

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.
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Description

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.
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Comprehensive Description

Biology

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).
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Description

  •  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).

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    Distribution

    National Distribution

    Canada

    Origin: Native

    Regularity: Regularly occurring

    Currently: Present

    Confidence: Confident

    Type of Residency: Year-round

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

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    National Distribution

    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

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    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).

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    northern Quebec to Connecticut
    • North-West Atlantic Ocean species (NWARMS)
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    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).
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    Geographic Range

    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 )

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    Historic Range:


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    Western Atlantic, Eastern Atlantic, North Sea, Baltic Sea, Mediterranean Sea, North America and northern Europe; farmed elsewhere with escapees; also introduced elsewhere.
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    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.
    • Bigelow, H. B. and Schroeder, W. C., 1953; Page, L. M. and B. M. Burr, 1991; Billard, R., 1997; Drummond Sedgwick, S., 1982.
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    Range

    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.
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    Physical Description

    Morphology

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

    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

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    Size

    Length: 140 cm

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    Maximum size: 1500 mm TL
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    Max. size

    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)
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    to 150 cm TL; max. weight: 174 kg.
    • Bigelow, H. B. and Schroeder, W. C., 1953; Page, L. M. and B. M. Burr, 1991; Billard, R., 1997; Drummond Sedgwick, S., 1982.
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    Diagnostic Description

    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).
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    Ecology

    Habitat

    Habitat Type: Freshwater

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    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.

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    nektonic
    • North-West Atlantic Ocean species (NWARMS)
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    anadromous species; born in large, cool rivers, migrate to sea after 1-6 years, then return to natal rivers to spawn
    • North-West Atlantic Ocean species (NWARMS)
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    Habitat and Ecology

    Habitat and Ecology
    An anadramous species.

    Systems
    • Freshwater
    • Marine
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    Environment

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

    This taxon is one of a number of benthopelagic species, whose habitat includes the Seine River system of Western Europe. Benthopelagic fish are found near the bottom of the water column, feeding on benthos and zooplankton

    The Marne and Yonne exhibit the greatest torrential flows, due to the percentage of their courses underlain by impermeable strata, in combination with the river gradients. Although the Loing manifests the highest percentage of impermeable strata of all the tributaries, its low gradient mitigates against torrential velocities. Thus the majority of the Seine and its tributaries exhibit a relaxed generally even flow rate.

    Seine water pollutant loads of heavy metals, nutrients, sediment and bacteria are relatively high, especially influnced by wastewater and surface runoff from Paris and its suburbs. Parisian pollutant loadings are noted to be particularly high during periods of high rainfall, not only due to high runoff, but also from the inadequate sewage treatment facilities in periods of high combined wastewater/stormwater flow.

    Heavy metal concentrations at Poses weir reveal the following levels: copper, 1.9 milligrams per liter; cadmium, 32 mg/l; and lead, 456 mg/l. Concentrations of zinc are also quite high, making the Seine Estuary one of the most highly contaminated estuaries in the world with respect especially to lead and cadmium. Significant amounts of toxic pollutants are also attached to sediments deposited in the Seine during the last two centuries, including mercury, nickel, chromium, toluene, DDT and a variety of herbicides and pesticides. Downriver from Paris, significant quantites of ammonium are discharged into the Seine from effluent of the Achères wastewater treatment plant.

    There are a total of 37 fish species inhabiting the Seine, and another two taxa that are known to have been extirpated in modern times. Two of the largest aquatic fauna known to have lived in the Seine are now locally extinct: the 500 centimeter (cm) long sturgeon (Acipenser sturio) and the 83 cm long allis shad (Alosa alosa).



    The largest bentho-pelagic species occurring in the Seine are:

    * the introduced 105 cm silver carp (Hypophthalmichthys molitrix);

    * the native 120 cm barbel (Hypophthalmichthys molitrix);

    * the native 150 cm Atlantic salmon (Salmo salar); and,

    * the native 500 cm Wels catfish (Silurus glanis).

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    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

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    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.

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     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.
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    Benthopelagic; freshwater; brackish; marine; depth to 10 m. Spend first 6 years in freshwater, then move to ocean existence.
    • Bigelow, H. B. and Schroeder, W. C., 1953; Page, L. M. and B. M. Burr, 1991; Billard, R., 1997; Drummond Sedgwick, S., 1982.
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    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.
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    Migration

    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.

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    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.

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    Introduction

    This species has been introduced or released in Dutch waters.
    • Nijssen, H.; de Groot, S.J. (1987). De vissen van Nederland: systematische indeling, historisch overzicht, het ontstaan van de viskweek, uitheemse vissoorten, determineersleutels, beschrijvingen, afbeeldingen, literatuur, van alle in Nederlandse wateren voor komende zee- en zoetwatervissoorten [Fishes of the Netherlands: systematic classification, historical overview, origins of fish culture, non-indigenous species, determination keys, descriptions, drawings, literature references on all marine and freshwater fish species living in Dutch waters]. KNNV Uitgeverij: Utrecht, The Netherlands. ISBN 90-5011-006-1. 224 pp.
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    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.
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    Trophic Strategy

    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.

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    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.
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    Food Habits

    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)

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    Juveniles: mollusks, crustaceans, insects, and fish. Adults: squids, shrimps, and fish.
    • Bigelow, H. B. and Schroeder, W. C., 1953; Page, L. M. and B. M. Burr, 1991; Billard, R., 1997; Drummond Sedgwick, S., 1982.
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    Associations

    Known prey organisms

    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.
    • R. M. Badcock, 1949. Studies in stream life in tributaries of the Welsh Dee. J. Anim. Ecol. 18:193-208, from pp. 202-206 and Price, P. W., 1984, Insect Ecology, 2nd ed., New York: John Wiley, p. 23
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    Diseases and Parasites

    Epitheliocystis. Bacterial diseases
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    Enteric Redmouth Disease. Bacterial diseases
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    Edwardsiellosis. Bacterial diseases
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    Population Biology

    Global Abundance

    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.

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    Life History and Behavior

    Behavior

    Diet

    Feeds on mollusks, crustaceans, insects, squids, shrimps, herring, alewives and smelts
    • North-West Atlantic Ocean species (NWARMS)
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    Communication and Perception

    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

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    Life Cycle

    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).
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    Development

    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).

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    Life Expectancy

    Lifespan/Longevity

    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.

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    Lifespan, longevity, and ageing

    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).
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    Reproduction

    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).

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    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)

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    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.
    • Bigelow, H. B. and Schroeder, W. C., 1953; Page, L. M. and B. M. Burr, 1991; Billard, R., 1997; Drummond Sedgwick, S., 1982.
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    Evolution and Systematics

    Functional Adaptations

    Functional adaptation

    Fish thrives in freshwater and seawater: Atlantic salmon
     

    Salmon can spend part of their lives in freshwater and part in seawater due to adaptive changes in their physiology.

         
      "The Atlantic salmon (Salmo salar) begins its life in a river, in the wild mountain streams of Norway or Scotland, hatching from an egg there in springtime. The salmon usually spends up to four years in the river before beginning the outward phase of its marathon migration as a smolt (a young salmon ready to migrate to the sea), traveling downriver to the ocean. During this period, the smolt's physiology adapts to enable it to live in seawater." (Shuker 2001:76)
      Learn more about this functional adaptation.
    • Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
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    Functional adaptation

    Olfactory sense pinpoints spawning river: Atlantic salmon
     

    Salmon identify a specific spawning river using their keen olfactory sense.

       
      "The salmon's extraordinary ability to locate the river where it was born is due to its highly developed olfactory sense, which enables it to distinguish between different rivers by scent." (Shuker 2001:76)
      Learn more about this functional adaptation.
    • Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
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    Molecular Biology and Genetics

    Molecular Biology

    Statistics of barcoding coverage: Salmo salar

    Barcode of Life Data Systems (BOLDS) Stats
    Public Records: 121
    Specimens with Barcodes: 155
    Species With Barcodes: 1
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    Barcode data: Salmo salar

    The following is a representative barcode sequence, the centroid of all available sequences for this species.


    There are 114 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

    CGATGATTTTTCTCAACCAACCACAAAGACATTGGCACCCTCTATTTAGTATTTGGTGCCTGAGCCGGAATAGTCGGCACCGCCCTA---AGTCTCTTGATTCGAGCAGAACTCAGCCAGCCTGGCGCCCTTCTGGGAGAT---GACCAAATTTATAACGTAATTGTTACAGCCCATGCCTTCGTCATAATTTTCTTTATAGTCATACCGATTATGATCGGCGGCTTTGGAAACTGATTAATTCCTCTTATA---ATCGGGGCCCCCGACATAGCATTCCCCCGAATGAATAACATAAGTTTTTGACTTCTCCCTCCCTCCTTTCTTCTCCTCCTGGCCTCATCTGGAGTTGAAGCCGGCGCTGGCACCGGATGAACAGTCTACCCCCCTCTAGCAGGTAATCTTGCCCACGCAGGAGCTTCCGTTGACTTA---ACTATTTTTTCCCTCCATTTGGCTGGTATTTCTTCAATTCTTGGGGCCATTAATTTTATTACAACCATTATGAATATAAAACCCCCAGCTATCTCTCAGTATCAAACCCCACTTTTTGTTTGAGCTGTATTAGTCACTGCCGTCCTTTTGTTACTCTCCCTCCCTGTTCTAGCAGCA---GGCATTACCATACTACTTACAGACCGAAATCTAAATACCACTTTCTTTGACCCGGCAGGCGGAGGAGACCCAATCTTGTACCAACATCTCTTTTGGTTCTTTGGCCATCCAGAAGTCTATATTCTCATTCTCCCAGGCTTTGGTATAATTTCACACATCGTTGCATACTACTCTGGCAAAAAA---GAACCTTTCGGGTACATAGGAATAGTCTGAGCTATGATAGCCATCGGACTCTTAGGTTTTATCGTTTGAGCCCACCATATGTTTACTGTCGGGATAGATGTAGACACTCGTGCCTACTTCACATCTGCCACT------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------TTC
    -- end --

    Download FASTA File
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    Genomic DNA is available from 14 specimens with morphological vouchers housed at British Antarctic Survey
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    Conservation

    Conservation Status

    National NatureServe Conservation Status

    Canada

    Rounded National Status Rank: NNR - Unranked

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    NatureServe Conservation Status

    Rounded Global Status Rank: TNR - Not Yet Ranked

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    National NatureServe Conservation Status

    Canada

    Rounded National Status Rank: N4 - Apparently Secure

    United States

    Rounded National Status Rank: N4 - Apparently Secure

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    NatureServe Conservation Status

    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.

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    IUCN Red List Assessment


    Red List Category
    LR/lc
    Lower Risk/least concern

    Red List Criteria

    Version
    2.3

    Year Assessed
    1996
    • Needs updating

    Assessor/s
    World Conservation Monitoring Centre

    Reviewer/s

    Contributor/s
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    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

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    North America's population of large salmon is at its lowest point in history. Declining numbers and loss of whole stocks in some rivers are causing increasing concern. Habitat destruction, denial of access to spawning grounds by dams and other obstructions, overfishing (including high-seas fishing and poaching), pollution, and especially acid rain are taking their toll. Cooperation and compromise by the major groups harvesting Atlantic salmon are essential if native stocks are to be saved. Scientific research has led to the creation of artificial spawning channels which provide a significant supplement to the production of salmon from natural streams. The Atlantic Salmon Federation is the largest, most effective organization devoted to the conservation of the Atlantic salmon and its habitat. This group has been successful in reducing commercial salmon fishing and some salmon streams have reported encouraging increases in the number of returning sea run fish as a result (Scott and Crossman, 1973; Atlantic Salmon Federation, 1996). Atlantic salmon are listed as lower risk by the IUCN, and they are considered an endangered species by the U.S. Fish and Wildlife Service.

    US Federal List: endangered

    CITES: no special status

    State of Michigan List: no special status

    IUCN Red List of Threatened Species: lower risk - least concern

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    Status

    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).
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    Threats

    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.

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    Lower Risk: least concern (LR/lc)
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    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.
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    Management

    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."

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    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).

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    Conservation

    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.
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    Relevance to Humans and Ecosystems

    Benefits

    Importance

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

    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).

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    Risks

    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).

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    Wikipedia

    Atlantic salmon

    Atlantic salmon

    The Atlantic salmon, Salmo salar, is a fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and, due to human introduction, the north Pacific.[2][3]

    Other names used to reference Atlantic salmon are: bay salmon, black salmon, caplin-scull salmon, Sebago salmon, silver salmon, fiddler, or outside salmon. At different points in their maturation and life cycle, they are known as parr, smolt, grilse, grilt, kelt, slink, and spring salmon. Atlantic salmon that don't journey to sea, usually because of past human interference, are known as landlocked salmon or ouananiche.

    Life stages[edit]

    Most Atlantic salmon follow an anadromous fish migration pattern,[3] in that they undergo their greatest feeding and growth in salt water; however, adults return to spawn in native freshwater streams where the eggs hatch and juveniles grow through several distinct stages.

    Atlantic salmon do not require salt water. Numerous examples of fully freshwater (i.e., "landlocked") populations of the species exist throughout the Northern Hemisphere.[3] In North America, the landlocked strains are frequently known as ouananiche.

    Freshwater phase[edit]

    The freshwater phases of Atlantic salmon vary between one and eight years, variably according to river location.[4] While the young in southern rivers, such as those to the English Channel, are only one year old when they leave, those further north, such as in Scottish rivers, can be over four years old, and in Ungava Bay, northern Quebec, smolts as old as eight years have been encountered.[4] The average age correlates to temperature exceeding 7 °C (45 °F).[2]

    The first phase is the alevin stage, when the fish stay in the breeding ground and use the remaining nutrients in their yolk sacs. During this developmental stage, their young gills develop and they become active hunters. Next is the fry stage, where the fish grow and subsequently leave the breeding ground in search of food. During this time, they move to areas with higher prey concentration. The final freshwater stage is when they develop into parr, in which they prepare for the trek to the Atlantic Ocean.

    During these times, the Atlantic salmon are very susceptible to predation. Nearly 40% are eaten by trout alone. Other predators include other fish and birds.[citation needed]

    Saltwater phases[edit]

    When parr develop into smolt, they begin the trip to the ocean, which predominantly happens between March and June. Migration allows acclimation to the changing salinity. Once ready, young smolt leave, preferring an ebb tide.

    Having left their natal streams, they experience a period of rapid growth during the one to four years they live in the ocean. Typically, Atlantic salmon migrate from their home streams to an area on the continental plate off West Greenland. During this time, they face predation from humans, seals, Greenland sharks, skate, cod, and halibut. Some dolphins have been noticed playing with dead salmon, but it is still unclear whether they consume them.

    Once large enough, Atlantic salmon change into the grilse phase, when they become ready to return to the same freshwater tributary they departed from as smolts. After returning to their natal streams, the salmon will cease eating altogether prior to spawning. Although largely unknown, odor – the exact chemical signature of that stream – may play an important role in how salmon return to the area where they hatched. Once heavier than about 250 g, the fish no longer become prey for birds and many fish, although seals do prey upon them. Grey and common seals commonly eat Atlantic salmon. Survivability to this stage has been estimated at between 14 and 53%.[2]

    Nomenclature[edit]

    The Atlantic salmon was given its scientific binomial name by zoologist and taxonomist Carolus Linnaeus in 1758. Later, the differently coloured smolts were found to be the same species.

    The name, Salmo salar, is from the Latin salmo, meaning salmon, and salar, meaning leaper, according to M. Barton,[5] but more likely meaning "resident of salt water". Lewis and Short's Latin Dictionary (Clarendon Press, Oxford, 1879) translates salar as a kind of trout from its use in the Idylls of the poet Ausonius (4th century CE).

    Physiology[edit]

    This is a fairly large salmonid; after 2 years at sea they measure 71 to 76 cm (28 to 30 in) long and weighing 3.6 to 5.4 kg (7.9 to 11.9 lb) on average.[6] Record-sized specimens have been measured to a maximum of 153 cm (60 in) and a weight of 45 kg (99 lb).[7] The colouration of young Atlantic salmon does not resemble their adult stage. While they live in fresh water, they have blue and red spots. While they mature, they take on a silver-blue sheen. When adult, the easiest way of identifying them is by the black spots predominantly above the lateral line, although the caudal fin is usually unspotted. When they reproduce, males take on a slight green or red colouration. The salmon has a fusiform body, and well-developed teeth. All fins, save the adipose, are bordered with black.

    Distribution and habitat[edit]

    Ocean migration of Atlantic salmon from Connecticut River[8]

    The distribution of Atlantic Salmon is temperature dependent. Because of global warming, some southern populations in Spain and other warm countries are expected to be extirpated soon. Before human influence, the natural breeding grounds of Atlantic Salmon were rivers in Europe and the Eastern coast of North America. When North America was settled by Europeans, eggs were brought on trains to the West coast and introduced in the rivers there. Other attempts to bring Atlantic salmon to new settlements were made; e.g. New Zealand. But since there are no suitable ocean currents on New Zealand, most of these introductions failed. There is at least one landlocked population of Atlantic salmon on New Zealand, where the fish never go out to sea.

    Young salmon spend 1–4 years in their natal river. When they are large enough (ca. 15 cm), they smoltify which means they undergo a physiological change where they change camouflage from stream-adapted with large gray spots to sea-adapted with shiny sides. They also undergo some endocrinological changes which means they adapt for the change in osmosis from fresh water to salt water. Finally, the parr (young fish) will finish smoltification by swimming with the current instead of swimming against the current. When this change of behavior occurs, they are no longer called parr, but are referred to as smolt. When the smolt reach the sea, they follow sea surface currents and feed on plankton or fry from other fish species such as herring. During their time at sea, they can sense the change in the Earth magnetic field through iron in their lateral line.

    When they have had a year of good growth, they will move to the sea surface currents that transport them back to their natal river. It is a major misconception that salmon swim thousands of kilometers at sea; instead they surf through sea surface currents. When they reach their natal river they find it by smell; only 5% of Atlantic salmon go up the wrong river. Thus, the habitat of Atlantic salmon is the river where they are born and the sea surface currents that are connected to that river in a circular path.

    Wild salmon disappeared from many rivers during the twentieth century due to overfishing and habitat change.[2] By 2000 the numbers of Atlantic salmon had dropped to critically low levels.[9]

    Diet[edit]

    Young salmon begin a feeding response within a few days. After the yolk sac is absorbed by the body, they begin to hunt. Juveniles start with tiny invertebrates, but as they mature, they may occasionally eat small fish. During this time, they hunt both in the substrate and in the current. Some have been known to eat salmon eggs. The most commonly eaten foods include caddisflies, blackflies, mayflies, and stoneflies.[2]

    As adults, the fish feed on much larger food: Arctic squid, sand eels, amphipods, Arctic shrimp, and sometimes herring, and the fishes' size increases dramatically.[2]

    Behaviour[edit]

    Fry and parr have been said to be territorial, but evidence showing them to guard territories is inconclusive. While they may occasionally be aggressive towards each other, the social hierarchy is still unclear. Many have been found to school, especially when leaving the estuary.

    Adult Atlantic salmon are considered much more aggressive than other salmon, and are more likely to attack other fish than others. Where they have become an invasive threat, attacking native salmon, such as Chinook salmon and coho salmon, has become a concern.[2]

    Breeding[edit]

    See also: Salmon run

    Atlantic salmon breed in the rivers of Western Europe from northern Portugal north to Norway, Iceland, and Greenland, and the east coast of North America from Connecticut in the United States north to northern Labrador and Arctic Canada.

    Many Atlantic salmon escape from cages at sea. These salmon tend to lessen the genetic diversity of the species leading to lower survival rates, and lower catch rates. On the west coast of North America, the non-native salmon can be an invasive threat, especially in Alaska and parts of Canada. This causes them to compete with native salmon for resources. Extensive efforts are underway to prevent the spread of Atlantic salmon in the Pacific and elsewhere.[10]

    The species constructs a nest or "redd" in the gravel bed of a stream. The female creates a powerful downdraught of water with her tail near the gravel to excavate a depression. After she and a male fish have eggs and milt (sperm), respectively, upstream of the depression, the female again uses her tail, this time to shift gravel to cover the eggs and milt which have lodged in the depression.

    Unlike the various Pacific salmon species which die after spawning (semelparous), the Atlantic salmon is iteroparous, which means the fish may recondition themselves and return to the sea to repeat the migration and spawning pattern several times, although most spawn only once or twice.[3][11] Migration and spawning exact an enormous physiological toll on individuals, such that repeat spawners are the exception rather than the norm.[11] Atlantic salmon show high diversity in age of maturity and may mature as parr, one- to five-sea-winter fish, and in rare instances, at older sea ages. This variety of ages can occur in the same population, constituting a ‘bet hedging’ strategy against variation in stream flows. So in a drought year, some fish of a given age will not return to spawn, allowing that generation other, wetter years in which to spawn.[4]

    Hybridization[edit]

    When in shared breeding habitats, Atlantic salmon will hybridize with brown trout (Salmo trutta).[12][13][14] Hybrids between Atlantic salmon and brown trout were detected in two of four watersheds studied in northern [Spain]. The proportions of hybrids in samples of 'salmon' ranged from 0 to 7-7% but they were not significantly heterogeneous among locations, resulting in a mean hybridization rate of 2-3%. This is the highest rate of natural hybridization so far reported and is significantly greater than rates observed elsewhere in Europe.[15]

    Aquaculture[edit]

    In its natal streams, Atlantic salmon are considered prized recreational fish, pursued by fly anglers during its annual runs. At one time, the species supported an important commercial fishery and a supplemental food fishery. However, the wild Atlantic salmon fishery is commercially dead; after extensive habitat damage and overfishing, wild fish make up only 0.5% of the Atlantic salmon available in world fish markets. The rest are farmed, predominantly from aquaculture in Norway, Chile, Canada, the UK, Ireland, Faroe Islands, Russia and Tasmania in Australia. Sport fishing communities, mainly from Iceland and Scandinavia, have joined in the North Atlantic Salmon Fund to buy away commercial quotas in an effort to save the wild species of Salmo salar.[11]

    Process[edit]

    A salmon farm holds yearlings for up to two years; many hold broodstock for even longer in these conditions to help ensure large, sexually mature adults. As is the case with this British Columbia farm, a majority of salmon farms are located in waters where Atlantic salmon is not native and risk becoming an invasive species upon release or escape.

    Adult male and female fish are anaesthetised; their eggs and sperm are "stripped" after the fish are cleaned and cloth dried. Sperm and eggs are mixed, washed, and placed into fresh water. Adults recover in flowing, clean, well-aerated water.[16] Some researchers have even studied cryopreservation of their eggs.[17]

    Fry are generally reared in large freshwater tanks for 12 to 20 months. Once the fish have reached the smolt phase, they are taken out to sea, where they are held for up to two years. During this time, the fish grow and mature in large cages off the coasts of Canada, the USA, or parts of Europe.[11]

    Generally, cages are made of two nets. Inner nets, which wrap around the cages, hold the salmon. Outer nets, which are held by floats, keep predators out.[16]

    Controversy[edit]

    In the past, some Atlantic salmon have escaped from cages at sea. In the Atlantic Ocean, this has resulted in some breeding with native populations, but generally most surviving offspring were from the domesticated Atlantics, not hybrids.

    On the West Coast of Northern America, aquaculturists have taken great care to ensure the non-native salmon cannot escape from their open-net pens, and escape is no longer considered a major concern. Evidence of Atlantic salmon surviving and establishing wild populations in the Pacific is lacking.

    From 1905 until 1935, in excess of 8.6 million Atlantic salmon of various life stages (predominantly advanced fry) were intentionally introduced to more than 60 individual BC lakes and streams. Historical records indicate, in a few instances, mature sea-run Atlantic salmon were captured in the Cowichan River; however, a self-sustaining population never materialized. Environmental assessments by the US National Marine Fisheries Service (NMFS), the Washington Department of Fish and Wildlife and the BC Environmental Assessment Office have concluded the potential risk of Atlantic salmon colonization in the Pacific Northwest is low.[18]

    Human impact[edit]

    Seine fishing for salmon – Wenzel Hollar, 1607–1677

    Atlantic salmon were once abundant throughout the North Atlantic. European fishermen gillnetted for Atlantic salmon in rivers using hand-made nets for at least several centuries.[19] Wood and stone weirs along streams and ponds were used for millennia to harvest salmon in the rivers of Maine and New England,[20] and gillnetting was an early fishing technology in colonial America.[21]

    Human activities have heavily damaged salmon populations across their range. The major impacts were from overfishing and habitat change, and the new threat from competitive farmed fish. Salmon decline in Lake Ontario goes back to the 18th–19th centuries, due to logging and soil erosion, as well as dam and mill construction. By 1896, the species was declared extirpated from the lake.[22] When dams were constructed on the Oswego River, their spawning areas were cut off and they went extinct locally.

    In the 1950s, salmon from rivers in the United States and Canada, as well as from Europe, were discovered to gather in the sea around Greenland and the Faroe Islands. A commercial fishing industry was established, taking salmon using drift nets. After an initial series of record annual catches, the numbers crashed; between 1979 and 1990, catches fell from four million to 700,000.[23] Overfishing at sea is generally considered the primary factor.

    Beginning around 1990, the rates of Atlantic salmon mortality at sea more than doubled. In the western Atlantic, fewer than 100,000 of the important multiple sea-winter salmon were returning. Rivers of the coast of Maine, southern New Brunswick and much of mainland Nova Scotia saw runs drop precipitously, and even disappear. To find out more about the increased mortality rate, a concerted international effort has been organized by the North Atlantic Salmon Conservation Organization.[24]

    Possibly because of improvements in ocean feeding grounds, returns in 2008 were positive. On the Penobscot River in Maine, returns were about 940 in 2007, and by mid-July 2008, the return was 1,938. Similar stories were reported in rivers from Newfoundland to Quebec. In 2011, more than 3,100 salmon returned to the Penobscot, the most since 1986, and nearly 200 ascended the Narraguagus River, up from the low two digits just a decade before.[25]

    Recovery[edit]

    Around the North Atlantic, efforts to restore salmon to their native habitats are underway, with slow progress. Habitat restoration and protection are key to this process, but issues of excessive harvest and competition with farmed and escaped salmon are also primary considerations. In the Great Lakes, Atlantic salmon have been introduced successfully, but the percentage of salmon reproducing naturally is very low. Most are stocked annually. Atlantic salmon were native to Lake Ontario, but were extirpated by habitat loss and overfishing in the late 19th century. The state of New York has since stocked its adjoining rivers and tributaries, and in many cases does not allow active fishing.[3][10]

    In New England, many efforts are underway to restore salmon to the region by knocking down obsolete dams and updating others with fish ladders and other techniques that have proven effective in the West with Pacific salmon. There is some success thus far, with populations growing in the Penobscot and Connecticut Rivers. Lake Champlain now has Atlantic salmon. In Ontario, the Atlantic Salmon Restoration Program[26] was started in 2006, and is one of the largest freshwater conservation programs in North America. It has stocked Lake Ontario with over 700,000 young Atlantic salmon. In October 2007, salmon were video-recorded running in Toronto's Humber River by the Old Mill. In November 2007, a migrating salmon was observed in the Credit River.[22] There has also been some success in establishing Atlantic salmon in Fish Creek, a tributary of Oneida Lake in central New York.

    Atlantic salmon still remains a popular fish for human consumption.[3] It is commonly sold fresh, canned, or frozen.

    Beaver impact[edit]

    The decline in anadromous salmonid species over the last two to three centuries is correlated with the decline in the North American beaver and European beaver, although some fish and game departments continue to advocate removal of beaver dams as potential barriers to spawning runs. Migration of adult Atlantic salmon may be limited by beaver dams during periods of low stream flows, but the presence of juvenile Salmo salar upstream from the dams suggests the dams are penetrated by parr.[27] Downstream migration of Atlantic salmon smolts was similarly unaffected by beaver dams, even in periods of low flows.[27]

    A 2003 study of Atlantic salmon and sea-run brown trout/sea trout spawning in the Numedalslågen River and 51 of its tributaries in southeastern Norway were unhindered by beaver.[28] In a restored, third-order stream in northern Nova Scotia, beaver dams generally posed no barrier to Atlantic salmon migration except in the smallest upstream reaches in years of low flow where pools were not deep enough to enable the fish to leap the dam or without a column of water over-topping the dam for the fish to swim up.[29]

    The importance of winter habitat to salmonids afforded by beaver ponds may be especially important in streams of northerly latitudes without deep pools where ice cover makes contact with the bottom of shallow streams.[27] In addition, the up to eight-year-long residence time of juveniles in fresh water may make beaver-created permanent summer pools a crucial success factor for Atlantic salmon populations. In fact, two-year-old Atlantic salmon parr in beaver ponds in eastern Canada showed faster summer growth in length and mass and were in better condition than parr upstream or downstream from the pond.[30]

    Legislation[edit]

    The first laws regarding the Atlantic salmon were started nearly 800 years ago.[citation needed]

    England and Wales[edit]

    Edward I instituted a penalty for collecting salmon during certain times of the year. His son Edward II continued, regulating the construction of weirs. Enforcement was overseen by those appointed by the justices of the peace. Because of confusing laws and the appointed conservators having little power, most laws were barely enforced.

    Based on this, a royal commission was appointed in 1860 to thoroughly investigate the Atlantic salmon and the laws governing the species, resulting in the 1861 Salmon Fisheries Act. The act placed enforcement of the laws under the Home Office's control, but it was later transferred to the Board of Trade, and then later to the Board of Agriculture and Fisheries.

    Another act passed in 1865 imposed charges to fish and catch limits. It also caused the formation of local boards having jurisdiction over a certain river. The next significant act, passed in 1907, allowed the board to charge 'duties' to catch other freshwater fish, including trout.

    Despite legislation, board effects decreased until, in 1948, the River Boards Act gave authority of all freshwater fish and the prevention of pollution to one board per river. In total, it created 32 boards.

    In 1974, the 32 boards were reduced to 10 regional water authorities (RWAs). Although only the Northumbrian, Welsh, northwest and southwest RWA's had considerable salmon populations, all ten also cared for trout and freshwater eels.

    The Salmon and Freshwater Fisheries Act was passed in 1975. Among other things, it regulated fishing licences, seasons, and size limits, and banned obstructing the salmon's migratory paths.[2]

    Scotland[edit]

    Legislation in Scotland to help Atlantic salmon began in 1318 by Alexander II. It prohibited certain types of traps in rivers.

    During the 15th century, many laws were passed; many regulated fishing times, and worked to ensure smolts could safely pass downstream. James III even closed a meal mill because of its history of killing fish attracted to the wheel. Because the fish were held in such high regard, poachers were severely punished.

    More recent legislation has established commissioners who manage districts. Furthermore, the Salmon and Freshwater Fisheries Act in 1951 required the Secretary of State be given data about the catches of salmon and trout to help establish catch limits.[2][16]

    United States[edit]

    Several populations of Atlantic salmon are in serious decline, and are listed as endangered under the Endangered Species Act (ESA). Currently, runs of 11 rivers in Maine are on the list – Kennebec, Androscoggin, Penobscot, Sheepscot, Ducktrap, Cove Brook, Pleasant, Narraguagus, Machias, East Machias and Dennys. The Penobscot is the "anchor river" for Atlantic salmon populations in the US. Returns in 2008 have been around 2,000, more than double the 2007 return of 940.

    Section 9 of the ESA makes it illegal to take an endangered species of fish or wildlife. The definition of "take" is to "harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct".[31]

    Canada[edit]

    The federal government has prime responsibility for protecting the Atlantic salmon, but over the last generation, effort has continued to shift management as much as possible to provincial authorities through memoranda of understanding, for example. A new Atlantic salmon policy is in the works, and in the past three years,[when?] the government has attempted to pass a new version of the century-old Fisheries Act through Parliament.

    Federal legislation regarding at-risk populations is weak.[citation needed] Inner Bay of Fundy Atlantic salmon runs were declared endangered in 2000. As of 2008, no recovery plan is in place.

    It takes constant pressure from nongovernmental organizations, such as the Atlantic Salmon Federation, for improvements in management, and for initiatives to be considered. For example, the technology for mitigation of acid rain-affected rivers used in Norway is needed in 54 Nova Scotia rivers. Yet, an initiative of the ASF and the Nova Scotia Salmon Association raised the funds to get a project in place, in West River-Sheet Harbour.

    In Quebec, the daily catch limit for Atlantic salmon is one fish over 63 cm (25 in), two fish under 63 cm or one fish over and one under 63 cm, provided the smaller fish was the first one caught (a provision designed to prevent an angler from continuing to fish if a large fish is already in possession). The annual catch limit is seven Atlantic salmon of any size.

    NASCO[edit]

    The North Atlantic Salmon Conservation Organization is an international council made up of Canada, the European Union, Iceland, Norway, the Russian Federation, and the United States, with its headquarters in Edinburgh.[32] It was established in 1983 to help protect Atlantic salmon stocks, through the cooperation between nations. They work to restore habitat and promote conservation of the salmon.

    Sustainable consumption[edit]

    In 2010, Greenpeace International has added the Atlantic salmon to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries".[33]

    See also[edit]

    Notes[edit]

    1. ^ World Conservation Monitoring Centre (1996). "Salmo salar". IUCN Red List of Threatened Species. Version 2.3. International Union for Conservation of Nature. Retrieved 7 March 2011. 
    2. ^ a b c d e f g h i Shearer, W. (1992). The Atlantic Salmon. Halstead Press. 
    3. ^ a b c d e f The Audubon Society Field Guide to North American Fishes, Whales & Dolphins. Chanticleer Press. 1983. p. 395. 
    4. ^ a b c Klemetsen A, Amundsen P-A, Dempson JB, Jonsson B, Jonsson N, O’Connell MF, Mortensen E (2003). "Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): a review of aspects of their life histories". Ecology of Freshwater Fish. doi:10.1034/j.1600-0633.2003.00010.x. 
    5. ^ Barton, M.: "Biology of Fishes.", pages 198–202 Thompson Brooks/Cole 2007
    6. ^ [1]
    7. ^ Burnie D and Wilson DE (Eds.), Animal: The Definitive Visual Guide to the World's Wildlife. DK Adult (2005), ISBN 0789477645
    8. ^ Atlantic Salmon Life Cycle Connecticut River Coordinator's Office, U.S. Fish and Wildlife Service. Updated: 13 September 2010.
    9. ^ . B. Dempson, C. J. Schwarz, D. G. Reddin, M. F. O’Connell, C. C. Mullins, and C. E. Bourgeois (2001). "Estimation of marine exploitation rates on Atlantic salmon (Salmo salar L.) stocks in Newfoundland, Canada". ICES Journal of Marine Science: 331–341. Retrieved 7 May 2011. 
    10. ^ a b Mills, D. (1989). Ecology and Management of Atlantic Salmon. Springer-Verlag. 
    11. ^ a b c d Heen, K. (1993). Salmon Aquaculture. Halstead Press. 
    12. ^ Youngson, A. F., Webb, J. H., Thompson, C. E., and Knox, D. 1993. Spawning of escaped farmed Atlantic salmon (Salmo salar): hybridization of females with brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences, 50:1986-1990.
    13. ^ Matthews, M. A., Poole, W. R., Thompson, C. E., McKillen, J., Ferguson, A., Hindar, K., and Wheelan, K. F. 2000. Incidence of hybridization between Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in Ireland. Fisheries Management and Ecology, 7:337-347.
    14. ^ Seawater tolerance in Atlantic salmon, Salmo salar L., brown trout, Salmo trutta L., and S. salar × S. trutta hybrids smolt. Urke HA, Koksvik J, Arnekleiv JV, Hindar K, Kroglund F, Kristensen T. Source Norwegian Institute of Water Research, 7462, Trondheim, Norway. henning.urke(@)niva.no
    15. ^ Natural hybridization between Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in northern Spain by Carlos Garcia de Leaniz
    16. ^ a b c Sedgwick, S. (1988). Salmon Farming Handbook. Fishing News Books LTD. 
    17. ^ N. Bromage (1995). Broodstock Management and Egg and Larval Quality. Blackwell Science. 
    18. ^ R. M. J. Ginetz (May 2002). "On the Risk of Colonization by Atlantic Salmon in BC waters" (PDF). B.C. Salmon Farmers Association. 
    19. ^ Jenkins, J. Geraint (1974). Nets and Coracles, p. 68. London, David and Charles.
    20. ^ "The River". The Penobscot River Restoration Trust. Retrieved 19 November 2013. 
    21. ^ Netboy, Anthony (1973) The Salmon: Their Fight for Survival, pp. 181-182. Boston, Houghton Mifflin.
    22. ^ a b Harb, M. "Upstream Battle", Canadian Geographic Magazine, June 2008, p. 24
    23. ^ "Salmon campaigner lands top award". BBC News. 22 April 2007. 
    24. ^ "Atlantic Salmon". animallist.weebly.com. Retrieved 19 November 2013. 
    25. ^ Carpenter, Murray (26 December 2011). "Shiny Patches in Maine’s Streambeds Are Bright Sign for Salmon". The New York Times. Retrieved February 2012. 
    26. ^ Atlantic Salmon Restoration Program
    27. ^ a b c P. Collen & R. J. Gibson (2001). "The general ecology of beavers (Castor spp.), as related to their influence on stream ecosystems and riparian habitats, and the subsequent effects on fish – a review" (PDF). Reviews in Fish Biology and Fisheries 10 (4): 439–461. doi:10.1023/A:1012262217012. 
    28. ^ Howard Park & Øystein Cock Rønning (2007). "Low potential for restraint of anadramous salmonid reproduction by beaver Castor fiber in the Numedalslågen river catchment, Norway". River Research and Applications 23 (7): 752–762. doi:10.1002/rra.1008. 
    29. ^ Barry A. Taylor, Charles MacInnis, Trevor A. Floyd (2010). "Influence of Rainfall and Beaver Dams on Upstream Movement of Spawning Atlantic Salmon in a Restored Brook in Nova Scotia, Canada". River Research and Applications: 183–193. doi:10.1002/rra.1252. 
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    32. ^ "NASCO ~ The North Atlantic Salmon Conservation Organization". Nasco.int. Retrieved 11 February 2012. 
    33. ^ Greenpeace International Seafood Red list

    References[edit]

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    Names and Taxonomy

    Taxonomy

    Comments: Distinct regional stocks have been identified using morphometric and biochemical characters (Claytor and McCrimmon 1988).

    See taxonomy comments for the Gulf of Maine population.

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