Mississippi River

Geology of the River

The Mississippi River borders Iowa for more than 300 miles, entering the state between swift bluffs that rise four to six hundred feet above the river level. Bluffs diminish in size and spectacular appearance from Bellevue southward. The river meanders east and west through many side channels, chutes, and sloughs across its two- to six-mile wide valley. 

From north to south along our entire border, the river becomes steadily wider - but shallower. The river bed is mostly sand and mud, with few bedrock outcroppings, the most notable are the Rock Island Rapids between  LeClaire and Davenport and the Keokuk Rapids above the mouth of the Des Moines River.

Appearance & Seasonal Changes

Mississippi waters become muddy during flooding. Much of the time, it is quite and clear, particularly in late summer, autumn and winter. Our part of the river flows about two miles per hour during normal water stages, but current speeds of up to five miles per hour are common during high water times.

The Mississippi River in its original appearance had a seemingly unending series of pools separated by shoals, bars and rapids, with a channel or series of channels between -- much like our larger interior streams today. These channels were blocked by rocks and snags which, during low water levels, separated into many side channels of narrow width and little depth until the stream took on a "braided" look.

Historical Improvements

• In 1824, Congress authorized improvement for navigation on the Mississippi River by removing snags and other channel obstructions. 
• As early as 1836, snags and steamboat wrecks were removed from the rapids at Keokuk and Rock Island. Shortly after, a canal and locks were built in the river at Keokuk. 
• In 1905, an act of Congress permitted construction of the Keokuk power dam. An act two years later authorized provisions of a six-foot channel for navigation from the Missouri River to Minneapolis by "construction works, dredging, diking, canals and locks." 
• In 1935, additional legislation was approved which authorized a nine-foot channel over the same river reach by means of locks and dams supplemented by dredging. The present dams that control the river resulted from this act. Engineering and environmental studies are currently being conducted to determine the feasibility of a twelve-foot navigation channel with year-long navigation.

Permanent Channel Dams

Eleven permanent channel dams affect the river bordering Iowa: 

• Lock and Dam No. 9, Lynxville 
• Lock and Dam No. 19, Keokuk
• Lock and Dam No. 10, Guttenberg
• Lock and Dam No. 11, Dubuque
• Lock and Dam No. 12, Bellevue
• Lock and Dam No. 13, Clinton
• Lock and Dam No. 14, LeClaire
• Lock and Dam No. 15, Quad-Cities
• Lock and Dam No. 16, Muscatine
• Lock and Dam No. 17, New Boston
• Lock and Dam No. 18, Burlington

Clams & Mussels

Unbelievable numbers of clams (freshwater mussels) of various kinds originally lived in the river. This abundance of clams was responsible for a huge pearl button industry, the largest in the world, centered at Muscatine. 

Before dam construction, millions of tons of shells were taken, but since the nine-foot channel was established, suitable habitat for mollusks has largely disappeared under heavy silt deposits. The remaining button industry is supported mostly from man-made materials. By the early 1930's, commercial clamming had almost disappeared along the Mississippi.

Development and use of prepared clam shell pieces in the culture of pearls revived clamming in the mid-1970`s, but clam harvest was nowhere near that at the turn of this century. The reported catch of clammers licensed in Iowa waters of the Mississippi in 1976 was less than 300 tons, which held stable into the 1980`s. Most of this harvest was exported to the Orient for the seeding of pearl clams in the culture of these valuable jewels.

Commercial Fishing

From an infant industry in the early river settlements, commercial fishing grew as the population in the midwest increased. Rapid transportation facilities and refrigeration, plus the introduction and establishment of carp in the 1880`s, put commercial fishing on the Mississippi River into a "big time" class. Commercial food-fish catches from the river provide a large proportion of the freshwater fish species eaten in the midwest and along the east coast today. Value of the fishery in Iowa exceeds well over one million dollars each year.

Fishing Statistics

The fishing industry on the Mississippi supports wholly or, in part, many families. Over the past forty years, the annual catch of fish has not changed much. 

• The average commercial fish harvest for the 5 year period between 1943-1948 was about three million pounds, the catch was made up of 
  • 47 percent carp
  • 22 percent buffalo
  • 15 percent catfish
  • 10 percent drum
  • 6 percent other species. 
• Between 1970-1982, total catch was slightly over 3.l million pounds each year. Species composition wa
  • 34 percent carp
  • 27 percent buffalo
  • 17 percent catfish
  • 15 percent drum
  • 7 percent miscellaneous species. 

The most dramatic change has been the number of commercial fishermen licensed. Before 1970, seldom were more than 400 licenses bought. But in the mid-70's, that number increased steadily until by 1983 over 2,250 Iowans were licensed to commercial fish - most in the Mississippi River. Over the years, the number of full-time commercial fishermen has declined to only a few, while the number of part-time operators has greatly increased.

Commercial Fishing Techniques

Most of the commercial fish species are taken with nets and seines, but large numbers of catfish are caught on trotlines in the river channel and backwaters and chutes. Commercial fishing is strictly regulated, with fishermen required to license all gear and equipment and report the number and kinds of fish taken. Catfish populations, which are intensively fished, are protected from over-harvest by a 15-inch minimum length limit. Before channelization of the Mississippi River, angling was much the same as that in the larger interior Iowa streams at the present time.

With construction of the six-foot navigation channel in 1907, large numbers of wing dams and channel training structures jutting out from the shore into the current to deepen the channel were built. This greatly changed earlier angling activities. Considerable fishing was done on the wing dams, where large numbers of crappie, northern pike, walleye, and smallmouth bass were taken. The wing dams, along with extensive shoreline rip-rapping, provided lush feeding spots for fish, and they gathered where small forage fish found food and shelter. The six-foot channel probably had very little effect on fishing in the rapid chutes between the numerous islands in the Mississippi. Here, too, large groups of foraging game fish were the source of excellent fishing. 

With establishment of the nine-foot channel dams, most of the wing dams were submerged. Most of the rapid chutes between islands and even the islands themselves were inundated by backwaters, forever destroying many of the formerly productive game fishing grounds.

With the navigation locks and dams creating a series of lake-type pools in the river, there was a decided change in the make-up of fish populations. Fast-flowing water fish species, such as smallmouth bass, declined in abundance, and fish that preferred more pond-like habitat, such as crappie, bluegill, walleye, carp and freshwater drum increased in abundance. The new channel dams also changed favorite fishing spots.

Best Fishing on the Mississippi

Best fishing for walleye, sauger, and paddlefish is directly in the tail race of the navigation dams, especially in late spring and fall. 

The popularity of fishing below the dams is accounted for by several basic factors that influence fish behavior. For most of each year, the dams are a physical barrier to fish movement - mostly in the upstream direction. For some distance below each structure, the bottom is scoured into a series of deep holes with diverse fish habitats, giving a particularly favorable bottom environment with highly oxygenated water. These conditions create excellent environment for forage fishes and other forms of fish food. 

Predacious sport fish concentrate in these havens of easy feeding. Most of the dams are easily accessible for fishing either from shore or by boat. Boat ramps and parking facilities are within a short distance of all Mississippi locks and dams. 

There are 58 launching sites on the Iowa side of the river. Public lands usually stretch a considerable distance downstream and are open to fishing. Some restrictions for safety are in effect at all dams and must be obeyed.