Rivers come in many sizes and shapes, provide habitat for many fish species. Different stretches of the same river can have contrasting personalities, producing entirely different aquatic flora and fauna. For example, a young, clear, coldwater river plunges from mountainous terrain, flowing over and cutting through bedrock. Here, trout, grayling, and whitefish thrive, but not crappies. The same river plunges into an area of hilly terrain. It widens and slows, becoming home to large trout, a few bass, pike, and walleyes—perhaps a few crappies in impoundments and in backwaters. Finally, the river empties into truly flat terrain, meandering easily, leaving its banks and creating new channels where soft substrates in the floodplain give way to create oxbow lakes, backwaters, and marshes. This is where crappies and species like largemouth bass, gar, and catfish thrive.

Middle-aged and old rivers are slow-flowing, shallow, and accompanied by broad floodplains. These wide floodplains create complex backwater areas with abundant habitat for crappies. Everywhere along the Mississippi River, for example—from Minnesota to Louisiana—backwater areas harbor excellent populations of crappies. Many of these backwaters have maximum depths of only 5 or 6 feet, but enough current finds its way in to reestablish oxygen content on a regular basis, while vast areas lie out of the current—the kind of habitat crappies utilize most in rivers. Brushpiles, stumpfields, deadfalls, and other woodcover are common crappie magnets within these areas.

RIVER CLASSIFICATION

Streams must be examined segment by segment. A stream can be shallow with only gradual gradient changes for miles, replete with backwaters, oxbows, and primarily soft-bottom habitat where crappies find an adequate home. Downstream, the river may cascade down a steep grade in the landscape, creating multiple sets of rapids, riffles, chutes, and falls—and harbor only trout. Eventually, the same stream could revert back to crappie-catfish water.

Rarely is a river the same from beginning to end, because few regions are topographically consistent. Because of these flow variations from fast to slow within the same river, we use the following method to classify rivers. “Very young” or “very old” are, perhaps, misnomers in most cases, as some old rivers run quite fast out of the Blue Ridge and Smokey mountains. The key is understanding gradient. The steeper the drop, the harder the bottom will be, as softer substrates are washed away by powerful currents. In flatter terrain, the sediments settle, covering the rock with sand and silt. Most river stretches in North America fall within one of seven categories. River stretches, though, often exhibit transitional tendencies, just as a natural lake may have eutrophic bays while its main body is mesotrophic.