lake trout

A freshwater food and game fish (Salvelinus namaycush) of the Great Lakes. Also called Mackinaw trout, namaycush; Also called togue.

Salvelinus namaycush

FAMILY

Salmonidae

TAXONOMY

Salmo namaycush Walbaum, 1792, Hudson Bay.

OTHER COMMON NAMES

English: Great Lake trout, lake charr, Mackinaw trout, salmon trout; French: Omble d'Amérique; German: Amerikanische Seeforelle; Spanish: Trucha lacustre; Inuktitut: Isuuq.

PHYSICAL CHARACTERISTICS

Average length 59 in (150 cm); average weight 72 lb (32.7 kg). Body typically troutlike, elongate, somewhat rounded, with a stout head that is dorsally broad. The deeply forked tail distinguishes them from other species. The lateral line is slightly curved at the front. Coloration characterized by white or yellowish spots on a dark green to grayish background, but also have pale spots on dorsal, adipose, and caudal fins, and usually on base of anal fin; sometimes orange-red on paired fins. During spawning males develop a dark lateral stripe and become paler on the back.

DISTRIBUTION

North America, from northern Canada and Alaska, south to New England in United States, and Great Lakes basin in Canada and the United States. Successfully introduced in many other areas, including South America, Europe, and New Zealand.

HABITAT

Shallow and deep waters of northern lakes and streams, rarely brackish waters.

BEHAVIOR

Sexually mature fishes return to the rocky creek where they were spawned in the same manner that river-living salmonids return home to their natal stream.

FEEDING ECOLOGY AND DIET

Extremely voracious. Most populations feed on freshwater sponges, crustaceans, insects, fishes, and small mammals; others feed on plankton throughout their lives. Planktivorous trouts show characteristics typical of plastic (variable) populations. For example, they grow more slowly, mature earlier and at smaller size, die sooner, and attain smaller maximum size than do their fish-eating counterparts. Vulnerable to larger fishes, otters, bears, and fish-eating birds.

REPRODUCTIVE BIOLOGY

More or less dispersed away from the spawning beds during the day, returning in late afternoon and spawning mostly at night, particularly between dusk and 9 or 10 P.M. Males establish their territory by rocks on the substrate, females arrive a few days later when males court them. From one to seven males will approach one to three females in the same area and press themselves against the sides of one or more females. Then the eggs fall into the crevices and the spawners disperse. This behavior is repeated until the female releases all her eggs. The eggs are heavy and sink to the bottom.

CONSERVATION STATUS

Not listed by the IUCN, yet they are highly susceptible to insecticides. In the 1930s sea lampreys invading the Great Lakes reduced this species almost to extinction. Great Lakes populations are largely sustained by extensive stocking of hatcheryreared fry.

SIGNIFICANCE TO HUMANS

Fished by both commercial and sport fishers.

For more information on lake trout, visit Britannica.com.

salvelinus namaycush.

For the band, see Lake Trout (band).

Lake trout
Salvelinus namaycush
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Salmoniformes Family: Salmonidae Genus: Salvelinus Species: S. namaycush
Binomial name
Salvelinus namaycush (Walbaum, 1792)

Lake trout (Salvelinus namaycush) is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, they can also be variously known as siscowet, paperbellies and leans. Lake trout are prized both as game fish and as food fish.

Lake trout are the largest of the trouts, the record weighing almost 46.3 kg (102 lb). They were fished commercially in the Great Lakes until lampreys, overharvest and pollution extirpated or severely reduced the stocks. Commercial fisheries still exist in some smaller lakes in northern Canada.

Lake trout are dependent on cold, oxygen-rich waters. They are pelagic during the period of summer stratification in dimictic lakes.

The lake trout is a slowly growing fish, typical of oligotrophic waters. It is also very late to mature. Populations are extremely susceptible to overexploitation. Many native lake trout populations have been severely damaged through the combined effects of hatchery stocking (planting) and overharvest.

A lake trout being held in an angler's hands.

It is generally accepted that there are two basic types of lake trout populations. Some lakes do not have pelagic forage fish during the period of summer stratification. In these lakes, lake trout take on a life history known as planktivory. Lake trout in planktivorous populations are highly abundant, grow very slowly and mature at relatively small size. In those lakes that do contain deep water forage, lake trout become piscivorous. Piscivorous lake trout grow much more quickly, mature at a larger size and are less abundant. Notwithstanding differences in abundance, the density of biomass of lake trout is fairly consistent in similar lakes, regardless of whether the lake trout populations they contain are planktivorous or piscivorous.

In Lake Superior, three distinct phenotypes of lake trout persist, commonly known as "siscowet", "paperbelly" and "lean". The distinct groups operate, to some level at least, under genetic control and are not mere environmental adaptations.^[1] Siscowet numbers, especially, have become greatly depressed over the years due to a combination of the extirpation of some of the fish's deep water coregonine prey and to overexploitation. Siscowet tend to grow extremely large and fat and attracted great commercial interest in the last century.

From a zoogeographical perspective, lake trout are quite rare. They are native only to the northern parts of North America, principally Canada but also Alaska and, to some extent, the northeastern United States. Lake trout have been introduced into many other parts of the world, mainly into Europe but also into South America and certain parts of Asia. In Canada, approximately 25% of the world's lake trout lakes are found in the province of Ontario. Even at that, only 1% of Ontario's lakes contain lake trout.

Lake trout have been known, very rarely, to hybridise in nature with the brook trout but such hybrids are almost invariably reproductively sterile. Hybrids are also artificially propagated in hatcheries and then planted into lakes in an effort to provide sport fishing opportunities.

The specific epithet namaycush derives from an indigenous North American name for the species, most likely in one of the Algonquian languages (c.f. Ojibwe: namegos = "lake trout"; namegoshens = "rainbow trout").

References

1. ^ Burnham-Curtis, M.K. and G.R. Smith, 1994. Osteological evidence of genetic divergence of lake trout (Salvelinus namaycush) in Lake Superior. Copeia (4):845-850.

• Salvelinus namaycush (TSN 162002). Integrated Taxonomic Information System. Accessed on 30 January 2006.

See also

• Lake Trout (band), a rock/ambient/jamband from Baltimore, Maryland.

External links

• Fishbase description of Lake trout

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