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Nearly half of the crayfish, freshwater fish, and amphibians in the Southern Appalachians are at risk of extinction (Smith et al. 2002).  Approximately 108 aquatic species in the ALCC are federally listed as threatened or endangered, due primarily to habitat degradation and population segmentation.  The Upper Tennessee River Basin is one of the most diverse aquatic habitats in the world and contains dozens of rare freshwater mussel species.  Many freshwater mussels are endangered due to water pollution and disturbance or destruction of their natural habitats.  In the last 150 years, there has been a steady decline in the number of freshwater mussels in the U.S. (Williams and Neves 1993).

Waterway alterations in the Southeast have led to major mussel population declines and extirpations from large areas of many species’ historical ranges (USFWS 1985).  This is also true of other aquatic species.  Dams and their impounded waters present physical barriers to the natural dispersal of mussels, including emigration (dispersal) of host fishes, and isolation of surviving mussel populations in limited portions of their range. Small isolated aquatic populations are subject to natural random events (i.e., droughts, floods) and to changes in human activities and land use practices (i.e., urbanization, industrialization, mining, certain agricultural activities and practices, etc.).  These changes may severely impact aquatic habitats (Neves et al. 1997). Without avenues of emigration to less-affected watersheds, mussel populations gradually disappear where land use activities result in deterioration of aquatic habitats.

In addition, freshwater mussels, which require fast flowing, silt free streams and rivers in order to survive, are susceptible to adverse effects caused by siltation in waterways. The main causes of siltation are road construction, poor agricultural land management practices, and deforestation.  In addition to siltation, freshwater mussels are also threatened by heavy metals, agricultural chemical runoff, and acid mine drainage (Williams and Neves 1993).

The recent introduction of non-native mussel species poses another serious threat to freshwater mussel survival. In particular, the rapid expanse of the Zebra mussel and Asian clam ranges could pose a direct threat to endangered mussel populations within the United States.

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