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      Salmo salar (Photo: Anders Lamberg) - Click for full size   Salmo salar (Photo: Anders Lamberg) - Click for full size   Salmo salar (Photo: Anders Lamberg) - Click for full size
    Taxonomic name: Salmo salar Linnaeus, 1758
    Synonyms: Salmo brevipes Smitt, 1882, Salmo caerulescens Schmidt, 1795, Salmo goedenii Bloch, 1784, Salmo gracilis Couch, 1865, Salmo hamatus Cuvier, 1829, Salmo hardinii Günther, 1866, Salmo nobilis Olafsen, 1772, Salmo nobilis Pallas, 1814, Salmo ocla Nilsson, 1832, Salmo renatus Lacepède, 1803, Salmo rilla Lacepède, 1803, Salmo salar biennis Berg, 1912, Salmo salar brevipes relictus Berg, 1932, Salmo salar brevipes Smitt, 1882, Salmo salar europaeus Payne, Child & Forrest, 1971, Salmo salar saimensis Seppovaara, 1962, Salmo salar lacustris Hardin, 1862, Salmo salar Linnaeus, 1758, Salmo salmo Valenciennes, 1848, Salmo salmulus Walbaum, 1792, Trutta relicta Malmgren, 1863, Trutta salar (Linnaeus, 1758)
    Common names: alabalik atlantik (Turkish), Amerikanskiy atlanticheskiy losos' (Russian), Atlanterhavslaks (Danish), Atlantic salmon, Atlantic salmon (English), Atlantischer salmon (German), Atlantisk laks (Danish), black salmon (English), bradan, braddan, breeder (English), caplin-scull salmon (English), common atlantic salmon (English), echter lachs (German), fiddler (English), grayling (English), grilse (English), grilt (English), gullspångslax (Swedish), hengst (Dutch), hoplax (Icelandic), Ijle zalm (Dutch), Jacobzalm (Dutch), kapisalirksoak, kapisilik, kavisilik, kebleriksorsoak, kelt (English), kumaliq, kutenut lohi (Finnish), k'wit'thet (Salish), k'wolexw (Salish), lachs (German), laks (Danish), laks (Norwegian), laks atlantisk (Norwegian), landlocked salmon (English), las (German), lax (Icelandic), lax (Norwegian), lax (Swedish), lohi (Finnish), losos (Polish), losos (Russian), losos (Serbian), losos atlantsky (Czech), losos obecný (Czech), losos szlachetny a. atlantycki (Polish), N. Atlantic salmon (English), nedfaldslaks (Danish), ouananiche (English), ouinanish (English), outside salmon (English), parr (English), saama, saamakutaak, saamarug, sake masu-rui (Japanese), salmao (Portuguese), salmão (Portuguese), salmâo-do-atlântico (Portuguese), sãlmao-do-atlântico (Portuguese), salmling (German), salmo (Italian), salmó (Catalan), salmon (English), salmón (Spanish), salmón del atlántico (Spanish), salmon peel (English), salmone (Italian), salmone atlantico (Italian), salmone del reno (Italian), sâma, saumon atlantique (French), saumon d'eau douce (French), schaanexw (Salish), sea salmon (English), sebago salmon (English), semga (Russian), shamet skelex (Salish), shmexwalsh (Salish), silver salmon (English), sináech (Salish), skællaks (Danish), sk'wel'eng's schaanexw (Salish), slhop' schaanexw (Salish), slink (English), smolt (English), solomos (Greek), solomós (Greek), somon de atlantic, spak'ws schaanexw (Salish), spring fish (English), spring salmon (English), st'thkway' (Salish), tacon atlantique (French), unaniche, vraklax (Swedish), winnish (English), zalm (Dutch)
    Organism type: fish
    Salmo salar ranks among the most popularly cultivated fish in the world. Commercial stocks have inflicted significant impacts of wild populations of wild salmon and other fish by way of competition, hybridization, and spread of disease. Great care should be taken to protect these wild fish populations while cultivating S. salar.
    Occurs in:
    coastland, lakes, marine habitats, water courses
    Habitat description
    Salmo salar is an anadromous species which inhabits the benthopelgaic zone of freshwater watercourses and sea. Large, cool rivers with extensive, gravelly bottom headwaters are essential to early development. As they grow, older juveniles prefer deeper waters and faster currents. They spend 1-6 years in rivers before moving to sea in spring or summer when the sea surface temperature in coastal areas are above 8 °C. Although, some populations remain landlocked. While at sea, S. salar roam vast feeding ranges, preferring temperatures of 4-12 °C, for 1-5 years and grow quickly. They return to rivers in the autumn to spawn. Most were found to return to the same river in which they were spawned. S. salar may withstand depths of up to about 210 m and temperatures 0-28 °C for short periods of time (Renzi, 1999; Fiske, 2006; FishBase, 2009).
    General impacts
    The negative ecological impacts associated with Salmo salar seem to be limited only to domestic fish farm stocks. Sea cages used are prone to tearing from storms, human error, predators or other causes, resulting in the mass escape of fish annually. For example a single storm in Norway resulted in the release of 490,000 farmed Atlantic salmonwhose total weight exceded the wild salmon harvest there for a whole year. Domesticate farm stocks of S. salar that escape can wreak havoc on wild populations by spreading disease and parasites to, competing with, and hybridizing with native salmon and other fish. Fish farming also fouls sea waters with varies toxicants associated with and produced by fish cultivation (Alaskan Department of Fish and Game, 2002; Thorstad et al, 2006; Volpe, undated; Hindar et al, 2006) .

    Crowding fish in net pens increases stress, which makes them more susceptible to disease. Therefore, when outbreaks do occur they tend to spread rapidly through the captive population. Diseases that occur in captive populations, such as furunculosis and sea lice Lepeophtheirus salmonis can spread to wild fish (Alaskan Department of Fish and Game, 2002; Amundrud & Murray, 2009; Naylor et al, 2005).

    Escaped S. salar compete with wild populations and other native fishes for resources. Farmed salmon and hybrids (farm x wild) can be expected to interact and compete directly with wild fish for food, habitat, and territory. Farm juveniles are generally more aggressive and consume similar resources as wild fish. They grow faster than wild fish, which may give them a competitive advantage at some life stages (Thorstad et al, 2006).

    Farm-raised S. salar also hybridize with wild stocks and other fishes, thereby reducing the wild stock's ability to survive in the wild by changing the level of genetic variability and frequency and types of alleles in the gene pools. The extremely high abundance of espaced salmon can completely dominate wild populations, comprising up to 80% of all breeders in smaller wild populations. Such an influx in these genetically divergent farmed Atlantic salmon can have dire consequences to wild populations and their genetics (Thorstad et al, 2006; Hindar et al, 2006).

    The net 'walls' of sea cages or net pens allow virtually complete interaction between the farm and the surrounding environment. Therefore, clean, oxygenated water is free to pass into the net pen while uneaten food pellets, feces, antibiotics and toxic anti-foulants flow out. The exchange of clean water into the farm and dispersal of industrial wastes away from the farm means that the industry benefits from a subsidy from nature (Volpe, undated).
    The likelihood of S. salar establishing reproducing populations in introduced habitats is extremely low. Over 130 attempts to introduce Atlantic salmon across 32 states in the United States, over 60 attempts in British Columbia, Canada, several attempts in Tasmania, and numerous attempts in Chile have all failed (Thorstad et al, 2006).

    Salmo salar is an extremely important food fish with over 1,000,000 tons cultivated annually. S. salar comprises over 90% of farmed salmon and over 50% of total salmon harvested. It is also a highly desirable sport fish by anglers (FAO, 2009).
    The ecological impacts of Salmo salar stem from cultivated populations which exert negative impacts on wild S. salar and other fish populations within native and introduced ranges. These farmed populations may be considered invasive even in native locations as it affects the long-term survival or genetic variation of native species, or the integrity or sustainability of natural communities (Chadderton, 2001).
    Geographical range
    Native range: The native, wild distribution of Salmo salar includes the rivers and northern Atlantic Ocean bound by North America, Scandinavia, and Europe between 40° and 70°N (Gross, 1998).
    Known introduced range: Salmo salar is not known to have naturalised anywhere outside its native range. It is stocked and/or commercially cultivated in locations throughout the world that constitute introduced ranges even if they are within the native range of S. salar.
    Introduction pathways to new locations
    Aquaculture: The commercial culture of S. salar in sea-cages in Tasmania has recently become a major part of the aquaculture industry (Kailola et al. 1993). S. salar are also farmed commercially in fish farms in mainland south eastern Australia, primarily in New South Wales and Victoria (Cadwallader, 1996).
    Management information
    Preventative measures: The use of potentially invasive alien species for aquaculture and their accidental release/or escape can have negative impacts on native biodiversity and ecosystems. Hewitt et al, (2006) Alien Species in Aquaculture: Considerations for responsible use aims to first provide decision makers and managers with information on the existing international and regional regulations that address the use of alien species in aquaculture, either directly or indirectly; and three examples of national responses to this issue (Australia, New Zealand and Chile). The publication also provides recommendations for a ‘simple’ set of guidelines and principles for developing countries that can be applied at a regional or domestic level for the responsible management of Alien Species use in aquaculture development. These guidelines focus primarily on marine systems, however may equally be applied to freshwater.

    Copp et al, (2005) Risk identification and assessment of non-native freshwater fishes presents a conceptual risk assessment approach for freshwater fish species that addresses the first two elements (hazard identification, hazard assessment) of the UK environmental risk strategy. The paper presents a few worked examples of assessments on species to facilitate discussion. The electronic Decision-support tools- Invasive-species identification tool kits that includes a freshwater and marine fish invasives scoring kit are made available on the Cefas (Centre for Environment, Fisheries & Aquaculture Science) page for free download (subject to Crown Copyright (2007-2008)).

    The impacts of farmed Salmo salar may be prevented by a number of strategies and technologies. Care should be taken in choosing farm sites as to prevent or reduce the spread of infections diseases and parasites suchs as sea lice (Lepeophtheirus salmonis) to wild fish populations (Thorstad et al, 2006; Amundrud & Murray, 2009).

    Sterilization of farm stocks by high pressure induction of triploidy in newly fertilized eggs would reduce the effects of hybridization of escaped S. salar with wild populations and other fishes. It may also reduce the competive effects of these escapees as well. This practice may reduce their survival and growth rate, increase the likelihood of deformities and susceptibility to disease, and induce negative market reactions. Culture of triploid S. salar was attmpted and abandoned in Fundy, Canada due to high susceptibility to the infectious salmon anemia virus. However, promising studies on this method continue (Thorstad et al, 2006).

    Domestication of S. salar to the point that individuals can no longer breed or even survive in nature is another possible means of negating possible impacts of farmed stocks on wild populations. It would be a complicated and long term process to do so without comprimising characteristics necessary for a quality yeild (Thorstad et al, 2006).

    Physical: The establishment of protected zones that prohibit the cultivation of S. salar is a means of retaining unaffected wild populations of Atalntic salmon. Norway, the top cultivator of S. salar, maintains 29 national salmon fjords and 52 national salmon rivers where new Atlantic salmon farming is prohibited. This protects 75% of wild salmon within the country. Large zones without existing salmon farms exhibited the inteded effect, but existing farms were allowed to remain. Establishing these zones before salmon farms are begun is essential to the effectiveness of this method. Recapture of escaped farmed salmon has been deemed ineffective (Thorstad et al, 2006).

    Salmo salar spend up to 4 years in deep-sea feeding grounds feeding on pelagic species such as herring, sprat and squid (FAO, 2009).
    Renzi (1999) reports that, "S. salar spawn in late fall/early winter. 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 colour, 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 25.4cm. 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."
    Lifecycle stages
    The Alaskan Department of Fish and Game (2002) reports that, "Salmo salar spawn in medium to large rivers from fall through spring. Juveniles can spend up to three years in streams and rivers before they migrate to the sea where they then spend up to three more years before returning to their birthplace to spawn and continue the cycle. Some S. salar may survive the spawning event (Pacific salmon do not) and return to the ocean to spawn again".
    Reviewed by: Version 1: Dr John Volpe, Adjunct. University of Alberta Faculty of Biological Sciences Canada Dr John Volpe, Adjunct. University of Alberta Faculty of Biological Sciences Canada
    Principal sources: Alaskan Department of Fish and Game, 2002. Atlantic Salmon: White Paper - March 5 2002.
    Renzi, 1999. Salmo salar Atlantic salmon.
    Compiled by: Profile revision: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Tuesday, 11 April 2006

ISSG Landcare Research NBII IUCN University of Auckland