North Shore steams are beautiful but challenging habitats for trout. Unlike trout streams in other parts of the state, North Shore streams receive only limited amounts of flow from groundwater. As a result flows are unstable, surging after a rain and dwindling to a trickle during drought and the winter season. Because they lack spring water, the streams get very cold in winter. In fact, "anchor ice" sometimes forms on the bedrock of the streambed, harming aquatic life and habitat. In the summer some stretches get warmer than is best for trout.
In their lower reaches, these streams cascade over falls and steep rapids. As pretty as these features may be, they are difficult for trout which must find places of quiet water amid the turbulence. The volcanic bedrock over which they flow also lacks some minerals that drive production of bugs in the stream that are trout?s main food source, making food scarcer than in trout streams in other parts of Minnesota.
Despite their challenges, North Shore streams have two things in their favor. First is their cool, northern, lake-moderated climate. Second is the deep-forest bank cover, which shades the streams and keeps them cool. These influences keep these streams just cool enough to support trout.
Interestingly, trout are not native to the upper reaches of many North Shore streams. Historically, brook trout occupied Lake Superior and ascended the rivers only as far as the first barrier falls-usually less than a mile from the lake. During the last century brook trout been stocked above these natural barriers. The DNR presently stocks brook trout in heavily fished creeks in and near Duluth, though brook trout are self-sustaining in most North Shore streams. The small size of the streams and their low productivity limit the number of trout exceeding 12 inches. As one North Shore fisheries manager noted: "We can raise a lot of small fish." In the deeper water of seclude beaver ponds brook trout occasionally may reach up to two pounds. However, numerous beaver dams do more harm than good, warming the water and contributing to siltation. North Shore trout management sometimes includes breaching beaver dams.
In North Shore streams that provide marginal trout habitat, the DNR stocks brown trout, which can tolerate warmer water than brook trout. Some larger streams are stocked with young steelhead which migrate to the lake in two to three years, briefly returning to streams as adults in spring to spawn. Many North Shore streams have steelhead populations that are partially or fully supported by natural reproduction. northeastern Minnesota maps (updated Spring 2007).