OUTDOOR CORNER: CHANGES IN MIDDLE MISSISSIPPI RIVER AFFECT ANIMAL LIFE

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You may have hear the phrase, build it and they will come." I guess the reverse is also true, "take it away and they will leave."

These phases seem appropriate for the middle Mississippi River because much habitat has been taken from it resulting in fewer fish and wildlife resources.

The middle Mississippi River is defined by its two major tributaries, the Missouri and the Ohio River. St. Louis is where it begins, Cape Girardeau is in the lower third, and Cairo, Ill., is where it ends. That is a distance of 300 miles, all the way providing water, transportation and commerce to everyone living near it.

There has always been beautiful scenery and abundant animal life in and along the river. Habitat is where an animal lives and without habitat there is no animal. For some animals that live in or along the rivers, there is less space to live than was in the past.

Fish are a good example. That doesn't mean the river has a poor fishery. In fact, the river can provide some excellent angling opportunities year round. But we do know that we have lost some fish species and numbers of others have declined. These declines have probably occurred because of a loss of habitat.

There are different habitats for difference species of fish. Like people, fish need several habitats to eat, grow and rest. Some fish species can live in many different habitat types, whereas others have strict requirements. If you are a fish in the river, your place to live has been cut almost in half over the last 40 years. The width of the river has been reduced to maintain a deep channel for safe navigation.

To understand problems associated with habitat loss, biologists look for certain changes over time. For example, decreasing numbers of fish can indicate a problem, much like a low number of bushels of corn per acre of land indicates a harvest problem. Changes in numbers of fish and species present can come from a combination of many things. Overharvest, water quality, non-native fish introductions or habitat loss to name a few can all affect fish numbers.

The most difficult task is determining which problem is responsible and if it can be corrected. Water quality has improved in the river as a result of the Clean Water Act in the 1970's. Fisheries Management practices have reduced overharvest of some fish but not all. We may never know the full effect of non-native fish introductions on native fish. However, habitat issues have received little attention.

Habitat changes are a natural process in a river. In a natural state a river flows in curves and loops called meanders. However, alterations to the river now keep the processes within fixed banks. Channelization, flow control, flooding and erosion all affect habitat.

Some habitat changes have been obvious. Large rock dikes or wingdams extend from the bank to the main channel.

Rock or revetted banks armor much of the river's shoreline. Although these structures provide some habitat at times, their purpose was to deepen the channel to improve navigation.

Other habitat changes are not as obvious. Locks and dams occur in the river above St. Louis. Seasonal floods that historically occurred in the river are held back by the dams to prevent flooding. Many species of fish in the river used these floods as a stimulus for spawning and seasonal migration. Changes in amount and duration of flow affects not only what habitat is available, but also when some species use the habitat.

So how have habitat changes affected fish in the river? Surprisingly many fish species (over 100) can still be found in the river. Some fish have almost disappeared such as the pallid sturgeon and flathead chub. While less desirable species, like the common and bighead carp seem to be more common.

Perhaps the most critical change affecting fish has been the loss of side channel habitat. These are areas where the main flow splits and flows in a separate channel. Many of the side channels have been closed off to main river flow and have declined in area.

Knowing what habitat has been lost and comparing it to what we have now will provide a better understanding of needed habitat for fish in the river.

At least then we can say "we saved it and they stayed."

Dave Herzog is a fisheries management assistant with the Missouri Department of Conservation.