Surveys conducted to determine the attitudes and preferences of Iowa anglers in l975 and l98l showed about one in five fishing trips was to one of the interior rivers. This means, that on the average, more than 2.5 million activity days take place on these streams each season. Part of the popularity of our rivers and streams probably is due to the fact most of our cities, and therefore our greatest population, are adjacent to rivers. Stream fishing has a particular fascination to people who like elbow room, enjoy wildlife of a never-ending variety, and a different angling challenge to solve around every bend.

With the exception of our largest rivers, most streams headwater within the state, and a majority of them join with parent streams well within the boundaries of Iowa. All interior streams are a part of either the Mississippi or Missouri river drainages.

Most Iowa streams flow through and drain some of the richest and most intensively cultivated soils on this planet. Because of the nature of our soils, intensive farming of small grain crops and drainage, our flowing waters are subject to violent and sudden fluctuations. Intense storms or snow-melt runoff often cause complete valley flooding at certain periods of the year, while in others flows are greatly diminished until many rivers resemble a series of shallow pools joined only by a trickle. Heavy silt load carried from agricultural lands in high flow have caused a slow, but systematic, decline in some fish species while others are more abundant than ever.

In spite of some unfavorable characteristics, such as heavy sedimentation and agricultural chemical pollution, our streams are very rich in nutrients, and the primary production of life is great. Our streams probably produce a greater poundage of fish today than when the pioneers first knew them. Recent river studies have shown that fish populations of up to 6,000 pounds per mile are not uncommon in our interior streams.

During the last century, silt loads from the ever-increasing farming activity, particularly for corn and soybeans, have caused many changes in the quality of our rivers, and consequently the aquatic life that live there. Lighter soil particles have been carried away leaving the heavier sand particles along the bottom of the channel, covering valuable food-producing riffles, filling in the deep, sheltering pools and generally lowering fish habitat diversity. The headwaters of our streams are usually quite clear, less subject to water level fluctuations, and have larger populations of sight-feeding fish. Lower stream reaches tend to be turbid, subject to greater agricultural and industrial pollution, and as a result contain far more fish species tolerant of environmental degradation.