The commercial lake trout fishery in Lake Superior alone supported an annual commercial harvest of 2 million kg from 1920 to 1950. Overfishing and predation by the non-native sea lamprey, -Petromyzon marinus-, led to a sharp decline in the commercial take in the 1950's. Continued stocking since 1952, chemical control of the sea lamprey and the closing of the commercial fishery in the early 1960's has stabilized the population, but has not acheived the goal of restoring self-sustaining stocks that can support an annual harvest comparable to that of the 1930's and early 1940's. (Great Lakes Fishery Commission, 1996).
Success of the stocked fish has varied depending on the area. Due to this and other factors, the restoration plan for Lake Superior has changed from a program that concentrated heavily on stocking to a program that emphasized management of wild lake trout populations.
Continued mangement of the sea lamprey, stringent fishing controls and better survival of stocked fish will be key components of future restoration plans. (Great Lakes Fishery Commission, 1996).
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Although once an important commercial fish stock, lake trout levels in the Great Lakes dropped sharply during the 1950's. Lake trout are still highly valued as a sport fish and anglers who seek this species contribute to the regional economy of areas with fishable populations through the purchase of fishing licenses.
As juveniles, lake trout feed on zooplankton and small invertebrates. As they mature, their foraging patterns shift and the fish become opportunistic piscivores.
As adults, lake trout are generally pisciverous, feeding on a wide variety of pelagic prey species. In the Great Lakes region, alewives, smelt, sculpin and chubs make up a large portion of the lake trout diet (Wisconsin Sea Grant, 1999).
Due to the cold water and dissolved oxygen content requirements of the species, lake trout which persist in the southern edge of their range must move to deeper water areas in the warmer summer months. If preffered prey species are not present at these depths, lake trout may then resort to feeding on zooplankton and invertebrates. In habitats that support no pelagic prey species, lake trout must subsist entirely on these secondary food sources. These dietary conditions often produce a leaner trout which grows more slowly and reaches sexual maturity earlier (Vander Zanden, 1999)
The native range of the lake trout (also known as lakers, tongue trout, mackinaw trout and mountain trout) includes the cold water regions of northern Canada, Alaska, the Great Lakes and parts of New England. The species has been widely introduced outside its native range in many parts of the western United States and in other areas, including New Zealand, South America and Sweden (Page, 1991).
Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); neotropical (Introduced ); australian (Introduced )
Lake trout are a cold-water species requiring relatively high concentrations of dissolved oxygen for survival (Ryan, 1994).
Lake trout are the only major native 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, lake trout require deep water refugia, where preferred temperature ranges and oxygen levels exist. Although most often found in lakes, lake trout may inhabit large river systems that have the neccessary habitat characteristics.
Aquatic Biomes: lakes and ponds; rivers and streams
Average lifespan
Status: wild: 41.0 years.
Average lifespan
Status: captivity: 12.0 years.
Lake trout possess 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. Younger fish will have seven to twelve interrupted parr marks along their sides (Page, 1991). The species supports nine to twelve gill rakers and unlike their cousin the brook trout, -Salvelinus fontinalis-, lake trout do not have a black stripe on the anterior edge of their anal and pelvic fins (Wisconsin Sea Grant, 1999). Breeding males develop a dark, lateral stripe on their sides (Page, 1991).
Although an average weight of around 3kg is reported for this species, much larger fish are encountered, some weighing in excess of 27kg. These larger trout are thought to have lived for twenty years or more (Trout Angler's Society, 1999). Lake trout average 45 to 68cm in length, with unusual specimens reaching 126cm (Page, 1991).
Lake trout are known to hybridize with brook trout where the range of the two species overlap. The resulting hybrid, known as a splake, supports intermediate features.
Range mass: 0 to 0 kg.
Average mass: 3 kg.
Other Physical Features: bilateral symmetry
Perception Channels: tactile ; chemical
Lake trout are a slow-growing, late-maturing species with generally low reproductive potential (Shuter, 1998). Though long-lived, both males and females, on average, do not reach sexual maturity until six to eight years of age (Wisconsin Sea Grant, 1999). Research has indicated that environmental factors, such as lake size and dissolved solid concentrations, may play a role in the age of first maturity and overall repoductive success of the lake trout (Shuter, 1998).
Lake trout seek substrates of cobble, rubble or gravel in which to spawn. Males will fan the bottom clean of finer silt so that the fertilized eggs of the female can be deposited in the substrate. As a female enters a spawning area, several males engage in amplexus (clasping) with the female; in this way eggs and sperm are broadcast over the substrate. Spawning generally takes place in fall or early winter and most often at night (Moyle, 1976).
Because of the colder water habitats preferred by -S. namaycush-, fertilized eggs require a long time to hatch. Eggs overwinter for four to six months before hatching. The developing trout remain in the crevices of the spawing substrate until their yolk-sac is completely absorbed. These "fingerlings" then move into deeper waters in search of food, usually in the form of zooplankton.
Average age at sexual or reproductive maturity (male)
Sex: male: 4745 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 4927 days.
The lake trout (Salvelinus namaycush)[2] is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also be variously known as siscowet, paperbelly and lean. The lake trout is prized both as a game fish and as a food fish. Those caught with dark coloration may be called mud hens.[3]
It is the only member of the subgenus Cristovomer, which is more derived than the subgenus Baione (the most basal clade of Salvelinus, containing the brook trout (S. fontinalis) and silver trout (S. agasizii)) but still basal to the other members of Salvelinus.[4]
From a zoogeographical perspective, lake trout have a relatively narrow distribution. They are native only to the northern parts of North America, principally Canada, but also Alaska and, to some extent, the northeastern United States.[5] Lake trout have been widely introduced into non-native waters in North America[6] and into many other parts of the world, mainly Europe, but also into South America and certain parts of Asia. Although lake trout were introduced into Yellowstone National Park's Shoshone, Lewis and Heart lakes legally in the 1890s, they were illegally or accidentally introduced into Yellowstone Lake in the 1980s where they are now considered invasive.[7]
Lake trout are the largest of the chars; the record weighed almost 102 pounds (46 kg) (netted) with a length of 50 inches (130 cm), and 15–40-pound (6.8–18.1-kilogram) fish are not uncommon. The average length is 24–36 inches (61–91 centimetres). The largest caught on a rod and reel according to the IGFA was 72 pounds (33 kg), caught in Great Bear Lake in 1995 with a length of 59 inches (150 cm).[8]
Lake trout inhabit cold, oxygen-rich waters. They are pelagic during the period of summer stratification in dimictic lakes, often living at depths of 20–60 m (66–197 ft).
The lake trout is a slow-growing fish, typical of oligotrophic waters. It is also very late to mature. Populations are extremely susceptible to overfishing. Many native lake trout populations have been severely damaged through the combined effects of hatchery stocking (planting) and over harvest. Another threat to lake trout is acidification, which can have longterm effects on their populations through both direct harm and reduced prey populations (e.g. Mysis relicta).[9]
There are three subspecies of lake trout. There is the common lake trout (Salvelinus namaycush namaycush), the siscowet lake trout (Salvelinus namaycush siscowet), and the less common rush lake trout (Salvelinus namaycush huronicus). Some lakes do not have pelagic forage fish during the period of summer stratification. In these lakes, lake trout act as planktivores. Lake trout in planktivorous populations are highly abundant, grow very slowly and mature at relatively small sizes. 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, common lake trout (S. n. namaycush) and siscowet lake trout (S. n. siscowet) live together. Common lake trout tend to stay in shallower waters, while siscowet lake trout stay in deeper water. Common lake trout (also called "lean" lake trout) are slimmer than the relatively fat siscowet. Siscowet numbers 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. Their populations have rebounded since 1970, with one estimate putting the number in Lake Superior at 100 million. Professor of Zoology at the University of Wisconsin-Madison James Kitchell credits effective constraint of commercial fisheries and persistent sea lamprey (Petromyzon marinus) control for the successful recovery of Lake Superior's lake trout. "Looking at what has happened in the lake and the results of computer simulations, it is clear that lamprey control needs to continue if Lake Superior is to keep its lake trout."[10]
Lake trout are known to hybridize in nature with the brook trout; such hybrids, known as "splake", are normally sterile but self-sustaining populations exist in some lakes.[11] Splake are also artificially propagated in hatcheries, and then stocked into lakes in an effort to provide sport-fishing opportunities.[12]
Lake trout were fished commercially in the Great Lakes until lampreys, overharvest and pollution extirpated or severely reduced the stocks. Commercial fisheries still exist in some areas of the Great Lakes and smaller lakes in northern Canada. Commercial fishing by Ojibwe for Lake Trout in Lake Superior is permitted under various treaties and regulated by the Great Lakes Indian Fish & Wildlife Commission (GLIFWC).[13]
The specific epithet namaycush derives from namekush, a form of the word used in some inland Southern East Cree communities in referring to this species of fish. Other variations found in East Cree are kûkamâs[h], kûkamâw and kûkamesh.[14] Similar cognate words are found in Ojibwe: namegos = "lake trout"; namegoshens = "rainbow trout", literally meaning "little lake trout".[15]
Geneva, New York claims the title "Lake Trout Capital of the World," and holds an annual lake trout fishing derby.[16]
The lake trout (Salvelinus namaycush) is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also be variously known as siscowet, paperbelly and lean. The lake trout is prized both as a game fish and as a food fish. Those caught with dark coloration may be called mud hens.
