Salvelinus namaycush (lake trout)

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Title Adult Caption Salvelinus namaycush (lake trout); fisherman holding an adult lake trout, which is in spawning dress. Copyright Public Domain-USGOV-INTERIOR-FWS	Adult	Salvelinus namaycush (lake trout); fisherman holding an adult lake trout, which is in spawning dress.	Public Domain-USGOV-INTERIOR-FWS

Identity

Preferred Scientific Name

• Salvelinus namaycush (Walbaum, 1792)

Preferred Common Name

• lake trout

Other Scientific Names

• Cristivomer namaycush Walbaum, 1792
• Cristivomer namaycush (Walbaum, 1792)
• Cristovomer namayacush (Walbaum, 1792)
• Cristovomer namayacush Walbaum, 1792
• Salmo amethystinus Mitchill, 1818
• Salmo amethystinus Mitchill, 1818
• Salmo amethystus Mitchill, 1818
• Salmo amethystus Mitchill, 1818
• Salmo confinis DeKay, 1842
• Salmo confinis DeKay, 1842
• Salmo ferox Perley, 1852
• Salmo ferox Perley, 1852
• Salmo namaycush Walbaum, 1792
• Salmo namaycush Walbaum, 1792
• Salmo pallidus Rafinesque, 1817
• Salmo pallidus Rafinesque, 1817
• Salvelinus namaycush Walbaum, 1792

International Common Names

• English: char; great lake trout; great Lakes char; great Lakes trout; grey trout; lake charr; lake trout; laker; landlocked salmon; mackinaw; mackinaw trout; masamacush; mountain trout; namaycush; salmon trout; siscowet; taque; togue; touladi
• Spanish: trucha lacustre; trucha lacustre
• French: cristivomer; omble d'Amérique; omble du Canada; Omble du Canada; touladi; truite de lac d'Amérique; truite grise
• Russian: severoamerikanskiy kristivomer

Local Common Names

• Alaska: akalukpik; akalukpik; col-lic-puk; col-lic-puk; ikalukpik; ikalukpik; lake trout
• Argentina: trucha de lago
• Austria: Amerikanischer Seesaibling; lake trout
• British Columbia: hupin; k'wit'thet; k'wsech; shamet skelex; shmexwalsh; sk'wel'eng's schaanexw; slhop' schaanexw; spak'ws schaanexw
• Canada: Great Lakes char; Great Lakes trout; grey trout; idlorak; idlorak; ihok; ihok; iIuuraq; iIuuraq; ikhlorak; ikhlorak; ilortoq; ilortoq; islorak; islorak; isok; isok; isuuq; isuuq; isuuqiaq; isuuqiaq; isuuqiq; isuuqiq; isuuraaryuk; isuuraaryuk; isuuraq; isuuraq; ivitaruk; ivitaruk; keyteeleek; keyteeleek; lake charr; lake trout; laker; mackinaw trout; masamacush; mountain trout; naaqtuuq; naaqtuuq; näluarryuk; Näluarryuk; näluarryuk; namaycush; namekus; namekus; nauktoq; nauktoq; nemakos; nemakos; nemeks; nemeks; némèkus; némèkus; salmon trout; sigguayaq; sigguayaq; siscowet; siuktuuk; siyuktuuq; taque; togue; Touladi; truite grise
• Czech Republic: siven obrovký; siven obrovký
• Denmark: Amerikansk søørred; amerikansk søørred; canadarødding; Canadarødding; canadarøding; Canadarøding; kanadarødding; Kanadarødding; Kanadarøding; kanadarøding
• Finland: harmaanieriä; harmaanieriä
• France: cristivomer; omble d'Amérique; Omble du Canada; truite de lac d'Amérique
• Germany: Amerikanische Seeforelle
• Greenland: iclook; iclook; iqluq; iqluq
• Iceland: murta; murta
• Italy: trota di lago americana; trota di lago americana
• New Zealand: mackinaw trout
• Norway: canadaröye; Canadaröye; Canadarøye
• Portugal: salvelino-lacustre; salvelino-lacustre; truta-do-lago; truta-do-lago
• Quebec: ikhiloktok; ishioraliktâq; milaqkkâyoq
• Russian Federation: severoamerikanskiy kristivomer
• Serbia: pastrva
• Slovakia: sivon velký; sivon velký
• Spain: trucha lacustre
• Sweden: Canadaröding; canadaröding; Kanadaröding; kanadaröding
• Switzerland: amerikanische Seeforelle; Amerikanische Seeforelle
• UK: great lake trout; grey trout; lake trout; namaycush; togue; touladi
• USA: great lake trout; lake trout; siscowet
• Yugoslavia (Serbia and Montenegro): pastrva

Summary of Invasiveness

S. namaycush is a freshwater fish native to North America. It has been introduced to other areas within North America and to South America, Europe, New Zealand and Japan. It is a highly piscovourous top predator (Fuller, 2007) and competes with native fish for habitat and food. S. namaycush has been reported to be responsible for the decline numerous populations of cutthroat trout Oncorhynchus clarkii and has been reported to prey heavily on the Utah chub Gila atraria (Teuscher and Luecke, 1996). Predation by lake trout has been shown to be a major factor in the decline of kokanee O. nerka in Lake Chelan, Washington (Schoen et al., 2012).

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Chordata
•             Subphylum: Vertebrata
•                 Class: Actinopterygii
•                     Order: Salmoniformes
•                         Family: Salmonidae
•                             Genus: Salvelinus
•                                 Species: Salvelinus namaycush

Description

S. namaycush has a deeply forked caudal fin and a slate grey to greenish body with lighter undersides. Cream to yellow spots are generally present on the head, body and dorsal and caudal fins. The lower fins tend to be orange-red with a narrow white edge. The species has nine to twelve gill rakers. Breeding males will develop a dark stripe on their sides temporarily (Lenart, 2001).

The average weight of S. namaycush is about 3 kg, but individuals can grow to up 27 kg under appropriate conditions (Hubert et al., 1994). Average length of S. namaycush varies from 45 to 68 cm (Scott and Crossman, 1973).

Distribution

In its native range, S. namaycush is widely distributed from northern Canada to New England and the Great Lakes basin (Page and Burr, 1991). Its established introduced range within North America includes the US states of California, Colorado, Idaho, Massachusetts, North Dakota, South Dakota, Washington and Wyoming. S. namaycush has been introduced into other countries such as Argentina, Austria, Bolivia, Czech Republic, Denmark, Finland, France, Germany, Italy, Japan, Morocco, New Zealand, Norway, Peru, Slovakia, Spain, Sweden, Switzerland and the United Kingdom.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

S. namaycush has been intentionally stocked as a sport fish in the majority of its introductions, though Kaeding et al. (1996) suggested that it was illegally introduced into Yellowstone Lake, Wyoming, USA.

In the Great Lakes of North America, part of its native range, S. namaycush has been stocked to restore populations that had been severely reduced by the sea lamprey.

Introductions

Risk of Introduction

S. namaycush has been intentionally stocked as a sport fish in the majority of its introductions, and since it is still stocked intentionally this remains the most likely pathway for new introductions.

Habitat

S. namaycush is a cold-water species, preferring temperatures below 13°C and requiring relatively high concentrations of dissolved oxygen for survival (Ryan, 1994). S. namaycush is the only major native North American sport fish adapted to the deep, cold water of oligotrophic (low-nutrient) lakes, such as those often found in northern Canada and the northern Great Lakes region (Shuter, 1998). At the southern range of the species, S. namaycush requires deep-water refuges, where its preferred temperature ranges and oxygen levels exist. Residing exclusively in freshwater and most often found in lakes, S. namaycush might also inhabit large river systems that have the necessary habitat characteristics.

Habitat List

Biology and Ecology

Reproductive biology

Spawning occurs mostly at night, with peak activity between dusk and 9 or 10 pm (Royce, 1951; Martin, 1957). One or two males approach a female, press against her sides and quiver, causing the female to release eggs, which are then fertilized. A large female may contain up to 17,000 eggs.

The eggs, which are quite large, become lodged in crevices in the rubble bottom, where they remain for months before hatching. Unlike most other salmonid species, S. namaycush do create nests (redds) during spawning. Age at maturity varies widely from around 5 years in southern areas of its native range to more than 20 years in northern areas.

Longevity

S. namaycush tends to reach a maximum age of 25 years; however, the oldest fish on record, in the Northwest Territories (Canada), was aged at 65 years.

Activity patterns

In large water bodies such as the Great Lakes, S. namaycush may migrate up to 300 km (186 mi) to their spawning grounds.

Associations

Muzzall and Whelan (2011) reviewed the available literature for parasites of fish within the Great Lakes. Below is a list of all identified on S. namaycush:

Adult Cestoda: Eubothrium crassum (Cooper, 1919; Pearse, 1924); Eubothrium salvelini, (Amin, 1977; Muzzall, 1989; Wardle, 1933; Dechtiar and Christie, 1988; Bangham, 1955; Muzzall and Bowen, 2000).

Larval/Immature Cestoda: Proteocephalus sp. (Muzzall, 1989).

Adult Nematoda: Cystidicola farionis (Ward and Magath, 1916); Cystidicola farionis (Lankester and Smith, 1980; Dextrase, 1987); Cystidicola stigmatura (Wright, 1879; Leidy, 1886; Black, 1983; Dechtiar and Lawrie, 1988;); Cystidicoloides ephemeridarum (Dechtiar and Lawrie, 1988); Cystidicola stigmatura (Ward and Magath, 1916).

Adult Acanthocephala: Acanthocephalus dirus (Amin, 1977; 1985; Muzzall, 1989); Echinorhynchus leidyi (Pearse, 1924b); Echinorhynchus salmonis (Pearse, 1924; Hnath, 1969; Amin and Burrows, 1977; Amin, 1985; Dechtiar and Christie, 1988; Muzzall, 1989; ); Echinorhynchus lateralis (Dechtiar and Lawrie, 1988); Echinorhynchus salmonis (Dechtiar and Lawrie, 1988).

Adult Digenea: Crepidostomum farionis (Dechtiar and Lawrie, 1988) Monogenea: Discocotyle sagittata (Dechtiar and Lawrie, 1988).

Larval/Immature Digenea: Diplostomum spathaceum (Collins and Dechtiar, 1974; Dechtiar et al., 1988); Diplostomum sp. (Bangham, 1955; Muzzall and Bowen, 2000); Ichthyocotylurus intermedia (Collins and Dechtiar, 1974).

Hirudinea: Unidentified leeches (Pearse, 1924).

Copepoda: Salmincola extensus (Pearse, 1924); Salmincola siscowet (Dechtiar and Lawrie, 1988).

Natural Food Sources

Climate

Latitude/Altitude

Air Temperature

Water Tolerances

Natural Enemies

Notes on Natural Enemies

There are several natural enemies of S. namaycush reported in its native range, including lamprey species (Ichthyomyzon unicuspis and Petromyzon marinus) and fish (Ameiurus nebulosus, Lota lota and Prosopium cylindraceum). Smaller S. namaycush are potentially predated upon by ducks and other birds.

Means of Movement and Dispersal

Natural dispersal

In large water bodies such as the Great Lakes, S. namaycush may migrate up to 300 km (186 mi) to their spawning grounds.

Intentional introduction

S. namaycush is primarily bred, introduced and stocked for recreational fisheries worldwide (Fuller, 2007).

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

S. namaycush was once an important commercial fish in the Great Lakes but numbers dropped sharply during the 1950s due to overfishing and predation by the sea lamprey Petromyzon marinus (Houston and Kelso, 1990). S. namaycush is still highly valued as a sport fish by anglers worldwide (Lenart, 2001). Recreational fishing and tourism may create a demand not only for food, accommodation and transportation, but also for related recreational activities such as camping, boating and canoeing, all of which may provide economic opportunities locally.

Environmental Impact

The various introductions of S. namaycush within the USA has had detrimental effects on native biodiversity. Several species of fish have been affected not only by competition from S. namaycush but by predation as well, as this species is a top predator (Fuller, 2007). For instance, numerous populations of cutthroat trout (Oncorhynchus clarki) have either been eliminated (e.g. in Lake Tahoe, western USA) or severely reduced (e.g. in Yellowstone Lake, Wyoming, USA). S. namaycush introduced into Flaming Gorge Reservoir were found to prey heavily on the Utah chub Gila atraria (Teuscher and Luecke, 1996). Predation by lake trout was shown to be a major factor in the decline of kokanee Oncorhynchus nerka in Lake Chelan, Washington (Schoen et al., 2012).

Social Impact

S. namaycush is a highly sought after recreational fishing species throughout North America. 

Risk and Impact Factors

Impact mechanisms

• Competition
• Competition - monopolizing resources
• Hybridization
• Pest and disease transmission
• Predation

Impact outcomes

• Altered trophic level
• Conflict
• Damaged ecosystem services
• Negatively impacts aquaculture/fisheries
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

Invasiveness

• Abundant in its native range
• Capable of securing and ingesting a wide range of food
• Has a broad native range
• Has high reproductive potential
• Invasive in its native range
• Long lived
• Tolerant of shade

Likelihood of entry/control

• Difficult/costly to control
• Highly likely to be transported internationally deliberately
• Highly likely to be transported internationally illegally

Uses

S. namaycush is a highly valued sport fish by anglers worldwide (Lenart, 2001).

Uses List

General

• Sport (hunting, shooting, fishing, racing)

Similarities to Other Species/Conditions

S. namaycush looks similar to the brook trout, S. fontinalis; however, S. fontinalis can be distinguished by a black stripe on the anterior edge of their pelvic and anal fins (Lenart, 2001).

Prevention and Control

Eradication

Numerous techniques have been used in an attempt to eradicate S. namaycush. In Yellowstone national park, USA, gillnetting and trapping were deemed the most suitable management techniques for its control (Kaeding et al., 1996). Electrofishing was effective in managing populations of S. namaycush, and is undertaken yearly in Yellowstone Lake (Greater Yellowstone Science Learning Center, 2012). Cox et al. (2012) examined the efficacy of high intensity sound from a seismic air gun in reducing survival of S. namaycush embryos, finding increased mortality in embryos at close range and younger age.

Control

As established populations are difficult and costly to control, further introductions or stocking should be avoided.

Chemical control

The only effective method of fish eradication is the application of rotenone, a piscicide that is also toxic to non target species.

Monitoring and surveillance (incl. remote sensing)

Both radio and acoustic telemetry can be used.

References

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Links to Websites

Principal Source

Draft datasheet under review

Contributors

08/10/14 Original text by:

Michael Godard, consultant, Canada

Distribution Maps

• = Present, no further details
• = Evidence of pathogen
• = Widespread
• = Last reported
• = Localised
• = Presence unconfirmed
• = Confined and subject to quarantine
• = See regional map for distribution within the country
• = Occasional or few reports

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