Changes in Black Bass Population Characteristics after the Introduction of Alabama Bass in Lake Norman, North Carolina

Lake Norman, North Carolina, has a popular fishery for largemouth bass (Micropterus salmoides), but in 2001, annual surveys by Duke Energy documented the unauthorized introduction of Alabama bass (M. henshalli). Concerns over the effects of this introduction on the existing largemouth bass fishery prompted this study, the objective of which was to use the existing standardized sampling program to document expansion of the Alabama bass population and describe changes in the population characteristics of largemouth bass in Lake Norman. Following Alabama bass introduction, the species quickly spread throughout the main channel of the reservoir, with a concomitant decline in largemouth bass abundance, although mean total length of largemouth bass increased. While the sampling protocol used was effective at documenting the changes in the main reservoir channel population characteristics between the two species, it did not document population characteristics in all areas of the reservoir. Additional samples collected in 2010 and 2013 by the North Carolina Wildlife Resources Commission in the upper area of the reservoir indicated that largemouth bass remained dominant in creek and cove areas but not along the main reservoir channel. This study illustrates that, while standardized sampling is a sound method for comparing black bass population characteristics between specific areas of interest, the addition of other habitat areas may be necessary to address specific questions regarding whole reservoir changes in their population characteristics. Further, this study serves as a cautionary tale of the unintended consequences of illegal unauthorized introductions of non-native species on native congeners.

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