5.4 Agriculture and Aquaculture
Studies have shown that greater cattle access to wetlands contributes to a higher prev- alence of Frog Virus 3 (FV3) (Gray et al. 2007a) . Pathogenic relationships between cattle and amphibians can occur when suitable hosts are present in drinking water supplies. For example, American Bullfrogs are suitable hosts of the human pathogen Escherichia coli (E. coli), which can provide an exposure pathway between food safety and human consump- tion when cattle operations contaminate waters with amphibian populations (Gray et al. 2007b; Hickling 2011) . Tis 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 inva- sive species). Te aquaculture, aquarium, biological supply, and live-bait industries are potentially the most important vectors responsible for the introduction of nonnative cray- fshes throughout North America (Lodge et al. 2000; Kilian et al. 2009) . In Maryland, Red Swamp Crayfsh 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 crayfsh is likely to out-compete and dis- place 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. Te traits that are benefcial in an aquaculture setting may be detrimental to wild animals. Also, a strain of fsh or other aquatic organism from a par- ticular river basin may be genetically compromised by a cultured organism whose lineage is from a diferent river basin. Tis 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 afect 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 fsh raised in aquaculture, likely because the high densities associated with fsh farming increases exploitation of pathogenic bacteria (Johansen et al. 2011; Cervino et al. 2012) . About 150 diferent bac- terial pathogens associated with farmed and wild-caught fsh have been identifed (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) . Te incidence, prevalence, and origin of diseases are difcult to measure in wild populations and the complex relationships between host, pathogen, and the environment can be infuenced by many factors (McVicar 1997; Bakke and Harris 1998; Weir and
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2015 NC Wildlife Action Plan
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