Water Types

The oligotrophic lake, which produces oxygen through surface circulation, is ideally suited to the lake trout and its special needs. These lakes are extremely deep and offer very little shallow water for vegetation to establish and as a result have an abundance of oxygen deep within the hypolimnion. The oligotrophic lake is one of three types of lakes, classified by their physical aging process. Lakes are either young (oligotrophic), middle aged (mesotrophic), or old (eutrophic). A complete description of these types, along with illustrations, can be found in Unit 1 on page 7.

Although lake trout prefer the ideal conditions usually found in most oligotrophic lakes, they are tolerant of and many can be found in the middle-aged meso lakes, provided these lakes can stratify.

As already noted, optimum trout lakes should be around 100 feet deep with rocky reefs for spawning. Shallower lakes, unless they are fed by cool springs, do not have sufficient volume of cold water for trout populations. Although some trout enter the mouths of streams along the shores of Lake Superior, they do not travel upstream very far.

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