Hundreds of streams course Minnesota's woods and farmlands. They range from the Straight River near Park Rapids, with its rich silt beds, profuse mayfly hatches and large wild brown trout, to the marginal soft-water creeks of Pine County, some of which maintain trout only through stocking. The quality of these streams depends on suitable streambed geology, adequate groundwater, and compatible land use in the watershed. A good trout stream is a lucky mix of these ingredients that can be improved only within the limits of basic productivity.
Minnesota trout streams: A study in contrasts
North Shore streams and southeast streams differ in almost all ways that are important to trout. Many North Shore streams flow from warm water lakes that have northern pike and walleye populations. Joining small, brushy tributaries and racing through cool, shaded gorges, these creeks become cold enough in their middle reaches to support brook trout. In their lower reaches, below the barrier falls, they may support resident trout as well as steelhead, chinook salmon and other lake-run (or "anadromous") species.
Southeast trout streams rise from springs, and may support brook trout in their headwaters. Brown trout prevail in the middle reaches. Warm water tributaries, dependent on runoff, may join the main stream as it gradually changes from a trout stream to a warm water river harboring walleye, northern pike, bass and catfish.
Lakes Managed For Stream Trout
Though brook, brown and rainbow trout evolved to breed and live in streams, they grow bigger when they are put into lakes. So, the DNR stocks stream trout in about 160 lakes to give anglers a chance to catch trophy trout-brookies up to six pounds, rainbows up to 10 and browns as large as 16.
In selecting lakes for stream trout, the DNR looks for lakes that are cold, well-oxygenated and free of pollutants. Ideally, the basins have no inlets or outlets that would allow stocked trout to leave or other fish to enter the lake and eat the trout or compete with them for food. Because of the potential for competition between species, native fish are removed before trout are stocked. Consequently, only lakes with undesirable fish populations are chosen for "rehabilitation." Stocking continues regularly because rainbow and brown trout require current-washed gravel to spawn and can't reproduce in lakes. Brook trout are better adapted to lakes and can spawn where an upwelling of spring water in the lakebed washes the eggs, however, significant natural reproduction is rare.
Some large lakes are managed for both stream trout and native lake trout. Other lakes are "two-story" fisheries-the shallows occupied by warm water game fish (such as walleye, bass and sunfish), and the depths used by stream trout.
In addition to brook, brown and rainbow trout, the DNR stocks splake-a cross between the male brookie and female lake trout. Splake grow faster than lakers and bigger than brook trout. They are popular because they taste good and are easy to catch.
Anglers, ages 16 to 65 must by a trout stamp to fish on Minnesota's designated trout streams and lakes, including Lake Superior. Funds from stamp sales pay for habitat improvement, raising and stocking trout, and evaluating management actions through electrofishing, creel censuses and other methods.