4.2 Aquatic Communities
4.2.13.5 Impacts to Wildlife Appendix G provides a list of SGCN and other priority species for which there are knowl- edge gap and management concern priorities. Appendix H identifes SGCN that use reser- voirs and impoundments. Impoundments are major contributors to habitat degradation and fragmentation in aquatic ecosystems (Baxter, 1977; Dynesius and Nilsson, 1994; Downing et al. 2006) , threatening many freshwater taxa (Dudgeon et al. 2006) . Reservoir construction in the United States reached its peak in the 1960s (Pringle et al. 2000) and more than 50 years have passed since habitat alteration may have afected fsh populations in impounded riverine systems. Habitat modifcation, combined with stocking practices, has contributed to the replacement of unique local assemblages with widespread species that are better able to tolerate human activities, which can lead to homogenization of freshwater biota (Rahel 2002) . Comparison of historical and contemporary fsh assemblages indicate that the structure of fsh assemblages upstream of inundated reaches have been altered in most impounded systems (Franssen and Tobler 2013) . Te condition of stream ecosystems depends on the appropriate quantity, quality, timing, and temporal variability of water fow to which aquatic species have adapted (Pof et al. 1997; Bunn and Arthington 2002) . Water withdrawal can lead to reduced stream fow (Weiskel et al. 2007) , and the presence of impoundments can further impact temporal variability of stream fow through their water storage capacities (Pof et al. 1997) . Results from Kanno and Vokoun’s 2010 study of New England streams evaluating the efects of water withdrawals and impound- ments on fsh assemblages suggest that water withdrawals have contributed to measurable alterations of fsh assemblages. Tese impacts should be considered when developing in stream fow regulation and aquatic conservation (Kanno and Vokoun 2010) . In their 2011 study of the efects of a small dam on freshwater mussel growth in Alabama, Singer and Ganglof found numerous locations where mussels were abundant and larger in size in reaches immediately downstream from the small dams. Analysis of length-at-age data using multiple growth models found that mill reach mussels grew faster than both up- and downstream populations, and evidence suggests that this phenomenon is geograph- ically and taxonomically widespread in eastern North America. Tese results suggest that some small impoundments enhance conditions for freshwater mussel growth and some older dams may warrant protection or restoration if downstream reaches support imper- illed mussel populations (Singer and Ganglof 2011) . Termal stratifcation of impoundments occurs mostly during the warmer seasons, when direct solar radiation and increased air temperatures heat surface layers faster than deeper layers (Sherman 2000; Sherman et al. 2007) resulting in the formation of a lighter, warmer surface layer of water (epilimnion) and a cold bottom layer (hypolimnion) (Smith and Smith 1998) . Many impoundments have fxed-level of-takes that are situated below the thermocline, hence
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2015 NC Wildlife Action Plan
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