Chapter 5 Threats
contaminate waters with amphibian populations (Gray et al. 2007b; Hickling 2011) . This is another reason why agricultural producers need to restrict livestock access to aquatic environments.
5.4.2 Aquaculture - Anticipated Impacts Aquaculture operations are a potential source of accidental release of nonnative species that can become invasive in surface waters (see Section 5.10 for more information on invasive species). The aquaculture, aquarium, biological supply, and live-bait industries are potentially the most important vectors responsible for the introduction of nonnative crayfishes throughout North America (Lodge et al. 2000; Kilian et al. 2009) . In Maryland, Red Swamp Crayfish has become established in streams adjacent to all aquaculture ponds where it was introduced for commercial culture or for aquaculture-related research (Killian et al. 2009) . Studies in North Carolina indicate this aggressive crayfish is likely to out-compete and displace native species for shelter and other limited resources, thereby resulting in changes to the composition of aquatic communities (Cooper and Armstrong 2007; Killian et al. 2009) . Genetic contamination of wild stocks can occur by release or escape of hatchery organisms that breed with wild organisms. The traits that are beneficial in an aquaculture setting may be detrimental to wild animals. Also, a strain of fish or other aquatic organism from a particular river basin may be genetically compromised by a cultured organism whose lineage is from a different river basin. This is particularly an issue with some anadromous species, such as Striped Bass. Aquaculture operations can be a source of various pathogens and parasites that can affect wild populations (see Section 5.13 for more information on diseases and pathogens). Bacterial infection is reported as the main cause of disease-induced mortality of fish raised in aquaculture, likely because the high densities associated with fish farming increase exploitation of pathogenic bacteria (Johansen et al. 2011; Cervino et al. 2012) . About 150 different bacterial pathogens associated with farmed and wild-caught fish have been identified (Austin and Austin 2012; Richards 2014) , but disease transfer between farmed and wild stocks is poorly understood (Weir and Grant 2005; Cervino et al. 2012) . In many cases, pathogens in aquaculture can remain undetected until some stress makes the animal more susceptible to infection (Austin and Austin 2012; Richards 2014) . The incidence, prevalence, and origin of diseases are difficult to measure in wild populations, and the complex relationships between host, pathogen, and the environment can be influenced by many factors (McVicar 1997; Bakke and Harris 1998; Weir and Grant 2005; Hedrick 1998; Cervino et al. 2012) . Water discharges and stock escapes from aquaculture are therefore important sources of exposure for diseases and pathogens to native populations (Richards 2014) . 5.4.3 Silviculture - Anticipated Impacts Generally, silviculture is the science of managing forests or forest crops to meet diverse needs and values. For purposes of this section, the topic is focused on the management of tree plantations for wood fiber, timber, Christmas trees, or production of nonnative species for
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2025 NC Wildlife Action Plan
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