4.5 River Basins
• Freshwater mollusks are sufering even greater declines, with numerous mussel and aquatic snail species that formerly occurred in the southeast now presumed extinct (Neves et al. 1997) . • Among crustaceans listed as endangered or threatened in the United States, more than half are from the southeast (Schuster 1997) . • Twelve species of North Carolina crayfsh are listed as species of concern or rare in the state, with their small native range the primary factor in their vulnerability to habitat loss and competition (Clamp 1999; Taylor et al. 1996) . Treats specifc to crayfsh include pollu- tion and impoundment, but competition with nonindigenous species is also a primary threat to many species (Taylor et al. 1996) . National and regional causes of declines among all aquatic taxa are widely attributed to habitat destruction and degradation and the introduction of nonnative species (Williams et al. 1993; Taylor et al. 1996; Etnier 1997; Warren et al. 1997; Collen et al. 2014) . Te medium-sized rivers and creeks that provide important habitat for many aquatic species are frequently impounded and substrates have been altered by erosion and sedimentation. Habitat alteration from nonpoint source pollution and fow alteration (i.e., impoundments) is the primary cause of population declines for a large percentage of southeastern fshes considered imperiled (Etnier 1997; Collen et al. 2014) . Not surprisingly, nonpoint source pollution and the efects of dams and impoundments are also the leading historic and current threats to freshwater mollusks (Bogan 1993; Neves et al. 1997; Richter et al. 1997) . Te complex life cycles and habitat requirements of mussels make them especially vulnerable to these perturbations (Adams et al. 1990; Bogan 1993; Neves et al. 1997) . In North Carolina, threats to biodiversity are similar to those listed above and include point and nonpoint source pollution, hydrologic alteration, physical habitat manipulation, and pollution. In recent decades, water quality has improved in many watersheds that were his- torically polluted primarily by point source discharges; however, overall habitat degrada- tion continues to threaten the health of aquatic communities. Increased development and urbanization, poorly managed crop and animal agriculture, and mining have impacted aquatic systems with point and nonpoint source inputs. Impoundments on major rivers and tributaries drastically alter the hydrologic regime of many North Carolina waterways and result in habitat fragmentation, blockage of fsh migration routes, and physical habitat alterations. Te US Environmental Protection Agency (EPA) reports that North Carolina contains approximately 37,662 stream/river miles; 311,236 acres of lakes and impoundments; and 3,121 square miles of coastal bays (EPA 2013a) . Information summarized from a EPA Clean Watershed Needs Survey, NPDES permits, and water quality assessments indicates more than half of the rivers are rated as ‘impaired’ because they are not meeting biological
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2015 NC Wildlife Action Plan
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