| Lake trout | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Salmoniformes |
| Family: | Salmonidae |
| Genus: | Salvelinus |
| Subgenus: | Cristovomer Walbaum, 1792 |
| Species: | S. namaycush |
| Binomial name | |
| Salvelinus namaycush | |
Thelake trout (Salvelinus namaycush)[4] is a freshwaterchar living mainly in lakes in Northern North America. Other names for it includemackinaw,namaycush,lake char(orcharr),touladi,togue,laker, andgrey trout. InLake Superior, it can also be variously known assiscowet,paperbelly andlean. The lake trout is prized both as agame fish and as afood fish. Those caught with dark coloration may be calledmud hens.[5][better source needed]
It is the only member of the subgenusCristovomer, which is more derived than the subgenusBaione (the mostbasal clade ofSalvelinus, containing thebrook trout (S. fontinalis) andsilver trout (S. agasizii)) but still basal to the other members ofSalvelinus.[6]
Thespecific epithetnamaycush derives fromnamekush, a form of the word used in some inlandSouthern East Cree communities in referring to this species of fish. Other variations found in East Cree arekûkamâs[h],kûkamâw andkûkamesh.[7] Similar cognate words are found inOjibwe:namegos = "lake trout";namegoshens = "rainbow trout," literally meaning "little lake trout."[8]
From azoogeographical perspective, lake trout have a relatively narrow distribution. They are native only to the northern parts of North America, principally Canada, but alsoAlaska and, to some extent, the Northeastern United States.[9] Lake trout have been widely introduced into non-native waters in North America[10] 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 intoYellowstone National Park'sShoshone,Lewis andHeart lakes legally in the 1890s, they were illegally or accidentally introduced intoYellowstone Lake in the 1980s where they are now consideredinvasive.[11] They have also notably been introduced into theTahoe region, such as inLake Tahoe andDonner Lake.[12][13]
Lake trout have a commonSalmonidae body, with an elongated figure, a single dorsal andadipose fin, and lack spines on any of their fins. The pattern of lake trout is a uniform olive-grey, darker near the back, and white on the belly. They are covered in light beige or white spots along the body. The fins are yellow-ish, and may have white tips. During spawning, the belly becomes more yellow-orange, and the fins develop a red hue with more developed white edges. They have small but sharp teeth, which are more visible compared to other species of trout duringnon-spawning periods.
Lake trout are the largest of thechars; the record weighed almost 102 pounds (46 kg) with a length of 50 inches (130 cm), and was caught with agillnet.[14] 15–40-pound (6.8–18.1-kilogram) fish are not uncommon, and the average length is 24–36 inches (61–91 centimetres). The largest caught on a rod and reel according to theIGFA was 72 pounds (33 kg), caught inGreat Bear Lake in 1995 with a length of 59 inches (150 cm).[15] In the Tahoe region, the fish do not exceeded 36 pounds (16 kg), but are on average over 10 pounds (4.5 kg).[12][13]
Lake trout inhabit cold, oxygen-rich waters. They arepelagic during the period ofsummer stratification indimictic lakes, often living at depths of 20–60 m (66–197 ft).
The lake trout is a slow-growing fish, typical ofoligotrophic waters. It is also very late to mature. Populations are extremely susceptible tooverfishing. Many native lake trout populations have been severely damaged through the combined effects ofhatchery stocking (planting) and over harvest. Another threat to lake trout isacidification, which can have longterm effects on their populations through both direct harm and reduced prey populations (e.g.Mysis relicta).[16]
There are threesubspecies 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 havepelagicforage fish during the period of summer stratification.[17][full citation needed] In these lakes, lake trout act asplanktivores. Lake trout in planktivorous populations are highly abundant, grow very slowly andmature at relatively small sizes. In those lakes that do contain deep-water forage, lake trout becomepiscivorous. Piscivorous lake trout grow much more quickly, mature at a larger size and are less abundant. Notwithstanding differences in abundance, the density ofbiomass of lake trout is fairly consistent in similar lakes, regardless of whether the lake trout populations they contain are planktivorous or piscivorous.[citation needed]
InLake 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 theextirpation of some of the fish's deep watercoregonine prey and tooverexploitation. 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 theUniversity of Wisconsin-Madison James Kitchell credits effective constraint of commercial fisheries and persistentsea 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."[18]
Lake trout are known tohybridize in nature with thebrook trout (S. fontinalis); such hybrids, known as "splakes" (between a male brook and female lake trout) or the less common "brookinaw" (between a male lake and female brook trout,) are normallysterile but self-sustaining populations exist in some lakes.[19] Splake are also artificially propagated inhatcheries, and then stocked into lakes in an effort to provide sport-fishing opportunities.[20]
Lake trout werefished commercially in theGreat Lakes until lampreys,overharvest and pollutionextirpated or severely reduced thestocks. Commercial fisheries still exist in some areas of the Great Lakes and smaller lakes in northern Canada. Commercial fishing by Ottawa (Odawa) and Chippewa (Ojibwe) Indians for Lake Trout in Lake Michigan, Lake Huron andLake Superior is permitted under varioustreaties and co-managed and regulated by many tribes andGreat Lakes Indian Fish & Wildlife Commission (GLIFWC).[21]
When lake trout are caught and released, the experience can cause short-termphysiological and behavioural stress. Blood stress markers such ascortisol,lactate, andglucose increase after capture, particularly when fish fight for long periods, are exposed to air, or are angled from deep water[22][23]. Deep-water captures can also causebarotrauma (i.e., injuries caused by rapid changes in pressure), resulting in bloating or disorientation due to rapid pressure changes. These effects are more common in larger fish and in warm-water conditions[23].
Responses differ betweenice-angling andopen-water angling. During ice-angling, fish often show higher lactate and glucose levels, lowerblood pH, and loss of reflexes such asorientation and equilibrium, with some mortality observed after release[22]. In open-water, stress responses are generally brief and mild with minor mortality; gill tissues show temporary activation ofhsp70 stress genes, while othermetabolic processes return to normal within two days[24]. Differences are also influenced by factors such as sex, depth, and season[23]. Careful handling, limiting fight time, reducing air exposure, and avoiding deep-water captures can improve survival and recovery following release[22][23][24].
Geneva,New York claims the title "Lake Trout Capital of the World," and holds an annual lake trout fishing derby.[25]Baraga county inMichigan also hosts an annual "lake trout festival" in June.[26][27]
Trout and char of the world | ||
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| Trout of Europe andAtlantic basin Salmo |   .png) | |
| Trout of thePacific basin Oncorhynchus | ||
| True char Salvelinus | ||
 Media related toTrout at Wikimedia Commons | ||
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