Animal Diversity Web

Ge­o­graphic Range

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

Habi­tat

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

Phys­i­cal De­scrip­tion

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.

• Other Physical Features
• bilateral symmetry

• Range mass

  0 to 0 kg

  0.00 to 0.00 lb

• Average mass

  3 kg

  6.61 lb

Re­pro­duc­tion

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 (female)
  Sex: female

  4927 days

  AnAge

• Average age at sexual or reproductive maturity (male)
  Sex: male

  4745 days

  AnAge

Lifes­pan/Longevity

• Average lifespan
  Status: wild

  41.0 years

  Max Planck Institute for Demographic Research

• Average lifespan
  Status: captivity

  12.0 years

  Max Planck Institute for Demographic Research

Be­hav­ior

• Key Behaviors
• natatorial
• motile

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

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)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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.

Con­ser­va­tion Sta­tus

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).

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Stephen Lenart (au­thor), East­ern Michi­gan Uni­ver­sity, Cyn­thia Sims Parr (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Hansen [ED], M. 1996. A Lake Trout Restora­tion Plan For Lake Su­pe­rior. Ann Arbor: Great Lakes Fish­ery Com­mis­sion.

Moyle, P. 1976. In­land Fishes of Cal­i­for­nia. Berke­ley: Uni­ver­sity of Cal­i­for­nia Press.

Page, L., B. Burr. 1991. A Field Guide to Fresh­wa­ter Fishes: North Amer­ica north of Mex­ico. Boston: Houghton Mif­flin.

Ryan, P., T. Mar­shall. 1994. Niche De­f­i­n­i­tion for Lake Trout and Its Use to Iden­tify Pop­u­la­tions at Risk. Cana­dian Jour­nal of Fish­ery and Aquatic Sci­ence, 51: 2513-2519.

Shuter, B., M. Jones, R. Ko­rver, N. Lester. 1998. A gen­eral, life his­tory based model for re­gional man­age­ment of fish stocks.... Cana­dian Jour­nal of Fish­ery and Aquatic Sci­ence, 55: 2161-2177.

Uni­ver­sity of Wis­con­sin, S. 1999. "Fish of the Great Lakes by Wis­con­sin Sea Grant" (On-line). Ac­cessed De­cem­ber 13, 1999 at http://​www.​seagrant.​wisc.​edu/​communications/​publications/​fish.

Van­der Zan­den, J. 1999. "Que­bec Bio­di­ver­sity Web­site- Fishes of Que­bec" (On-line). Ac­cessed De­cem­ber 19, 1999 at http://​www.​redpath-museum.​mcgill.​ca/​Qbp/​fish/​specpages.