Marshes, by definition, are shallow bodies of water that sometimes go dry. Anyplace you see tall emergent vegetation such as cattails, you can be sure that the area was dry at sometime in the past. This is a safe assumption, because these plants normally will germinate only on mud flats, not under water.

Marshes, in fact go through a series of somewhat predictable stages: starting with the dry marsh, there is of course no water, no muskrats, and very few nesting or migratory birds. As water begins to return to the marsh, there will be shallow water, dense vegetation, few muskrats, and a few more birds. As more water returns, there will be less vegetation, more birds of all kinds and many more muskrats. In fact, when this stage reaches the 50:50 ratio of vegetation to open water, it is ideal. This ratio provides abundant nesting and migrating birds, abundant muskrats, and excellent hunting and trapping. The next stage in the normal marsh cycle, will be the "open marsh stage" which is characterized by mostly open water, declining muskrat numbers, few birds and rather poor hunting. The final marsh stage is "open water", which resembles a shallow lake. This is of little value to waterfowl, other wildlife or hunters. Any of these stages can last from one to five or more years.

Sure, we can just let Nature take its course, and on marshes without water level control, that's exactly what we have to do. Where we can regulate the water level, however, we attempt to maintain the marsh in the "middle", where we have plenty of vegetation, bird production, muskrats and waterfowl hunting. Sometimes this can be accomplished by minor changes in water levels, but more often it requires drastic measures.

Two of the biggest players in marsh management are muskrats and carp. Muskrats first. It is essential to have at least some muskrats present in most marshes if we have any hope of reaching and maintaining the marsh stage we want. The main reason the marsh goes from dense vegetation to open water is due to muskrats killing the vegetation as they use it for food and house building. For this reason we sometimes attempt to control muskrats (by Spring trapping, for example) to keep them - from becoming too abundant and ruining the marsh.

Carp often move into a marsh when it is in an ideal stage for other animals. If there are large numbers of carp, and there usually are, they make the water so turbid that plants cannot grow. They also destroy growing plants by rooting them out, and consume aquatic life that would otherwise have gone to feed ducks, blackbirds, rails, and other birds. Carp simply do not belong in a Iowa marshes.

Luckily, there is a technique that will get rid of the carp and allow plants to grow again. This is to drain or "draw-down" the area so that there is no surface water for at least one growing season. The carp will die or move downstream, and plants will germinate on the exposed mud flats.

Next the marsh needs to be re-filled with water. No matter what kind of water control structure we have, this depends on Mother Nature. It can take anywhere from a few days to several years to re-fill a drained marsh, depending on rainfall, watershed size, etc.

Finally, we hope to reach the "middle" or 50:50 stage that is so desirable to wildlife, and keep it there for as long as possible. When the marsh finally reaches the "open-water" stage (and it will), it is time to start the process all over. In the ideal situation (which rarely happens) none of these management decisions will be complicated by political "string-pulling", special interests or adverse weather.

In a nutshell, this is water level management on many Iowa marshes.

For further information regarding the water level management for wildlife contact Tom Neal at the Ruthven Wildlife Management Unit (712) 262-4177.

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