ECOS Guide to the Ecology of the Northern Rockies

Name: Salvelinus namaycush - Lake Trout

Family: Salmonidae (Trout and Salmon)

Order: Salmoniformes (Salmon/Trout/Pike)

Class: Osteichthyes (Bony Fishes)

Abundance: Patchy

Origin: Native

Active Season: Year Round

Size:

average: 22 inches
largest: 47 inches

Colors: red-orange (fins),white-gray (spots are lighter than body), green (slight tint on sides), blue-purple (slight tint on sides).

General Description: Like all members of the Salmonidae family, lake trout have adipose fins and a pelvic axillary process. Lake trout (as well as all trout species) have small scales and a large mouth. Lake trout in particular have very light spots on their bodies, and sometimes have wavy lines on their backs. They often have white edges on their fins, and fins are often slightly orange. Lastly, they have a deep fork in their tail (the lenght of the tail at the shortest point is less than half the length of the tail at the longest point).

Similar Species: Lake trout may be confused with bull trout, but bull trout tend to have fewer spots, and some spots may be red or brown. Lake trout, on the other hand, always have black spots, and have a more deeply forked tail. Lake trout may also be confused with brook trout, but brook trout have a square, mostly unforked tail, and their spots are surrounded by blue halos.

Life History: Lake trout spawn along the shorelines of lakes, usually in water between 10 and 120 feet deep. Interestingly, they spawn at night during the fall, and instead of laying their eggs in a gravel nest, or a redd, as many trout species do, they broadcast their eggs over a wide area. The lake trout eggs hatch in March or April when the temperature of the lake has warmed, and the young trout move almost immediately to deeper water. The young eat mainly plankton, and become sexually mature at seven or eight years of age. Lake trout usually live for about 20 years, but they have been known to live for 40 years!

Distribution: Lake trout are found in parts of Alaska, most of Canada, and many parts of the northern United States. In Montana, they are native to Elk Lake, Twin Lake, Saint Mary's Lake, and the Waterton Lakes. They have been introduced into other lakes, like Flathead Lake and Fort Peck Reservoir.

Habitat Description: Lake trout are found in deep, cold lakes and resevoirs.

Feeding Habits: Lake trout are the top predators in many lakes. The young mainly eat plankton while they are small, but larger trout eat aquatic insects, other fish, and even small mammals (like mice and shrews) and birds!

Enemies & Diseases: The Great Lakes once had a huge population of lake trout, and supported a booming fishing industry. The fishery has collapsed, however, due in part to predation by sea lampreys. Sea lampreys are originally from the Atlantic, and are large, parasitic, eel-like fish with sharp, circular mouthparts. The sea lampreys are capable of swimming very fast once they find a lake trout, and they use their mouthparts to attach themselves to the trout and suck out blood and other fluids. Unfortunately, lampreys kill many of their hosts or leave huge wounds on others. To protect the lake trout in the Great Lakes, barriers have been set up at entering tributaries that keep the lampreys out. As well, certain chemicals that kill lampreys but do not harm fish (these are calles "lampricides") are used. Besides lampreys, the other main predator of lake trout is humans. They are valued for their delicious, creamy flesh.

Did You Know: In Lake Superior, there are three main types of lake trout, each with a slightly different body shape, thought to help them survive in certain depths. The "lean" trout is slender, and is found in areas less than 70 meters deep. The "siscowet" trout is more robust, and is found in areas between 50 and 150 meters deep. The "humper" or "paperbelly" trout has a very thin abdominal wall and large eyes, and is found on shallow shoals (50 meters deep) surrounded by very deep water. Each types has different amounts of body fat, growth rates and body size, which are thought to help them survive in their particular depth.

Glossary:

Adipose fin: the small fin found on the topside of a fish nearest the tail fin.
Axillary process: the very small fin attatched to the pelvic fin.
Dorsal fin: the large fin on the topside of a fish.
Hybridize: the interbreeding of two different species.
Pelvic fin: the fin on the underside of the fish nearest the head.
Plankton: very small organisms (sometimes microscopic) that have no backbone and drift through the water.
Spawn: to deposit eggs.

Keywords:

References:

Alaska Department of Fish and Game. Wildlife Notebook. http://www.adfg.state.ak.us/pubs/notebook/fish/l^trout.php

Baggio, Anna. Sea Lamprey Information Page. http://www.science.mcmaster.ca/Biology/Harbour/SPECIES/SEALAMP/TITLE.HTM.

Burnham-Curtis, M. K., and G. R. Smith. 1944. Osteological evidence of genetic divergence of lake trout (Salvelinus namaychus) in Lake Superior. Copeia 1944: 843-850

Holton, G. D. and H. E. Johnson. 2003. A Field Guide to Montana Fishes, Third Edition. Montana Fish, Wildlife & Parks, Helena, MT.

Montana Fish, Wildlife, and Parks Animal Field Guide. Lake Trout. http://fwp.mt.gov/fieldguide/detail_AFCHA05050.aspx

Contributor:

Allison Greene


Home Plant Guide Insect Guide Bird Guide Mammal Guide Geology Guide Fish Guide Fish by Name Fish by Family Fish by Order Glossary of Fish Terms Amphibian Guide Reptile Guide Habitats Descriptions Maps Contributors ECOS Home		Physical Characteristics - General Description - Similar Species - Life History - Distribution - Habitat - Feeding Habits - Did You Know - Glossary - References Name: Salvelinus namaycush - Lake Trout Family: Salmonidae (Trout and Salmon) Order: Salmoniformes (Salmon/Trout/Pike) Class: Osteichthyes (Bony Fishes) Abundance: Patchy Origin: Native Active Season: Year Round Size: average: 22 inches largest: 47 inches Colors: red-orange (fins),white-gray (spots are lighter than body), green (slight tint on sides), blue-purple (slight tint on sides). General Description: Like all members of the Salmonidae family, lake trout have adipose fins and a pelvic axillary process. Lake trout (as well as all trout species) have small scales and a large mouth. Lake trout in particular have very light spots on their bodies, and sometimes have wavy lines on their backs. They often have white edges on their fins, and fins are often slightly orange. Lastly, they have a deep fork in their tail (the lenght of the tail at the shortest point is less than half the length of the tail at the longest point). Similar Species: Lake trout may be confused with bull trout, but bull trout tend to have fewer spots, and some spots may be red or brown. Lake trout, on the other hand, always have black spots, and have a more deeply forked tail. Lake trout may also be confused with brook trout, but brook trout have a square, mostly unforked tail, and their spots are surrounded by blue halos. Life History: Lake trout spawn along the shorelines of lakes, usually in water between 10 and 120 feet deep. Interestingly, they spawn at night during the fall, and instead of laying their eggs in a gravel nest, or a redd, as many trout species do, they broadcast their eggs over a wide area. The lake trout eggs hatch in March or April when the temperature of the lake has warmed, and the young trout move almost immediately to deeper water. The young eat mainly plankton, and become sexually mature at seven or eight years of age. Lake trout usually live for about 20 years, but they have been known to live for 40 years! Distribution: Lake trout are found in parts of Alaska, most of Canada, and many parts of the northern United States. In Montana, they are native to Elk Lake, Twin Lake, Saint Mary's Lake, and the Waterton Lakes. They have been introduced into other lakes, like Flathead Lake and Fort Peck Reservoir. Habitat Description: Lake trout are found in deep, cold lakes and resevoirs. Feeding Habits: Lake trout are the top predators in many lakes. The young mainly eat plankton while they are small, but larger trout eat aquatic insects, other fish, and even small mammals (like mice and shrews) and birds! Enemies & Diseases: The Great Lakes once had a huge population of lake trout, and supported a booming fishing industry. The fishery has collapsed, however, due in part to predation by sea lampreys. Sea lampreys are originally from the Atlantic, and are large, parasitic, eel-like fish with sharp, circular mouthparts. The sea lampreys are capable of swimming very fast once they find a lake trout, and they use their mouthparts to attach themselves to the trout and suck out blood and other fluids. Unfortunately, lampreys kill many of their hosts or leave huge wounds on others. To protect the lake trout in the Great Lakes, barriers have been set up at entering tributaries that keep the lampreys out. As well, certain chemicals that kill lampreys but do not harm fish (these are calles "lampricides") are used. Besides lampreys, the other main predator of lake trout is humans. They are valued for their delicious, creamy flesh. Did You Know: In Lake Superior, there are three main types of lake trout, each with a slightly different body shape, thought to help them survive in certain depths. The "lean" trout is slender, and is found in areas less than 70 meters deep. The "siscowet" trout is more robust, and is found in areas between 50 and 150 meters deep. The "humper" or "paperbelly" trout has a very thin abdominal wall and large eyes, and is found on shallow shoals (50 meters deep) surrounded by very deep water. Each types has different amounts of body fat, growth rates and body size, which are thought to help them survive in their particular depth. Glossary: Adipose fin: the small fin found on the topside of a fish nearest the tail fin. Axillary process: the very small fin attatched to the pelvic fin. Dorsal fin: the large fin on the topside of a fish. Hybridize: the interbreeding of two different species. Pelvic fin: the fin on the underside of the fish nearest the head. Plankton: very small organisms (sometimes microscopic) that have no backbone and drift through the water. Spawn: to deposit eggs. Keywords: References: Alaska Department of Fish and Game. Wildlife Notebook. http://www.adfg.state.ak.us/pubs/notebook/fish/l^trout.php Baggio, Anna. Sea Lamprey Information Page. http://www.science.mcmaster.ca/Biology/Harbour/SPECIES/SEALAMP/TITLE.HTM. Burnham-Curtis, M. K., and G. R. Smith. 1944. Osteological evidence of genetic divergence of lake trout (Salvelinus namaychus) in Lake Superior. Copeia 1944: 843-850 Holton, G. D. and H. E. Johnson. 2003. A Field Guide to Montana Fishes, Third Edition. Montana Fish, Wildlife & Parks, Helena, MT. Montana Fish, Wildlife, and Parks Animal Field Guide. Lake Trout. http://fwp.mt.gov/fieldguide/detail_AFCHA05050.aspx Contributor: Allison Greene