Some interesting info:
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 (60–200 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.
Two basic types of lake trout populations are generally accepted. Some lakes do not have
pelagic forage fish during the period of summer stratification. In these lakes, lake trout take on a life history known as
planktivory. 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, three distinct
phenotypes of lake trout persist, commonly known as "siscowet", "paperbelly" and "lean". The distinct groups operate, to some level at least, under genetic control and are not mere environmental adaptations.
[6] Siscowet numbers, especially, 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.
[7]
