Fish Facts » Lake Trout
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). 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.
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. 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.
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)
Lake trout were once a valued commercial fish in Lake Superior but were almost eliminated there by the sea lamprey, an exotic fish that attaches itself to other fish and eventually kills them. United States and Canada have worked together to reduce lamprey numbers. Most lake trout lakes are within the Boundary Waters Canoe Area Wilderness.
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).
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.
University of Michigan Museum of Zoology Animal Diversity Web, Minnesota Department of Natural Resources
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