Habitat Loss and Degradation

Habitat loss is the most significant problem impacting fish and wildlife populations today.  This threat is directly related to human population size and conflicting human uses of land and water.

It is essential that good stewardship be incorporated into development and land use practices to ensure that future generations enjoy a high quality of life.  As we begin to adopt the concepts of ecosystem management, it is very important to remember that we also are an important part of the ecosystem.  Our own health and well-being are directly related to the health and well-being of our ecosystem.  Species diversity is a direct reflection of ecosystem health.

As land is developed for industry and residential purposes, wildlife habitat is permanently lost.  The Ohio River has long been a prime source of water for many industries.  These industries require large volumes of water and, in some cases, large tracts of land.  Permanent barge mooring facilities also contribute to habitat loss.  Riverfront homes, cottages, and private docks are also being built at an ever-increasing rate.

Commercial dredging of sand and gravel directly from the bottom of the river permanently changes the aquatic habitat, and the species groups associated with these habitats.  Dredging operations are capable of removing gravel to a depth of 60 feet from the surface of the water.  If the river depth was 20 feet, then up to 40 feet of the river bottom can be removed during this process.  This changes the habitat from a shallow, productive environment where sunlight reaches the bottom to a deep, less productive environment.  Spawning habitat for walleye, sauger, and smallmouth bass is lost and resident freshwater mussel populations are destroyed in this process.  Unlike many of our natural resources, these gravel deposits are a nonrenewable resource.

Commercial dredging operations also re-suspend large volumes of sediment that travels with the current.  Clean, rocky substrates located downstream are smothered by these sediments.  Freshwater mussels and any species of fish or invertebrate requiring sediment-free surfaces are negatively impacted for long distances downstream from the actual dredging operations.

Damming the river to maintain a 12-foot deep navigation channel has caused special problems for the shallow backwater habitats of the Ohio River.  These shallow embayments have become settling basins for silt and sedimentation from all of the above mentioned sources.

Embayments are spawning and nursery habitat for some fish species and refuges for many others during the winter.  Largemouth bass, crappie, bluegills, and many minnow species require moderately shallow areas, out of the strong river currents, to spawn and raise their young.  The hot summer sun can heat these degraded embayments beyond the temperatures most fish can tolerate, making these areas unusable.  Fish, being cold-blooded, may have difficulty swimming in the river when the water temperature drops and seek refuge in embayments and backwaters during high-flow periods in the winter.

Hydropower generating plants are proposed for many of the Ohio River dams to meet the increasing demand for electricity.  These plants pose a double threat to Ohio River fish populations:  entrainment mortality and reduced oxygen levels during the summer.

Some fish species can be drawn into the generating turbines (entrainment) causing both internal and external injuries.  Fish air bladders can be ruptured when the fish pass through a turbine, because of pressure changes.  Fish can also suffer cuts and abrasions from the turbine blades.  The combination can result in significant fish mortality.

The concern with reduced oxygen levels is directly related to the fact that the Ohio River has been dammed, elimination the natural oxygen producing riffles that were once abundant.  The primary remaining source of physical oxygenation is from the water that flows over the dams.  During low flow periods it can take all of the river’s volume to power the hydro-turbines, with none left to flow over the dam and oxygenate the water.  Most low flow periods typically occur during the summer when oxygen demand is highest.