Harvest as a tool to manage populations of undesirable or overabundant fish and wildlife
Harvest is a common management tool for fish and game species and can also be used for overabundant populations when stakeholders want to reduce populations reduced and still provide recreational opportunities. The authors propose a framework to determine if harvest can be used to control populations when overabundance is an issue, stakeholders support harvest, information is available to set harvest goals and evaluate impacts of harvest, and assessments are conducted to evaluate unintended consequences of harvest. The chapter provides two case examples of mid-continent light geese and blue catfish in the Chesapeake Bay watershed, for which overabundance was a problem and stakeholders had interest in harvest. Substantial data existed to set goals for light geese whereas blue catfish data were limited. For both light geese and blue catfish, desired outcomes have not yet been achieved, but hunting and fishing opportunities generated societal benefits despite existing barriers to increasing harvest. Harvest to control overabundant populations can be a useful tool, but consideration of stakeholder support, the data require to establish and monitor goals, and unintended consequences should be considered for an effective harvest plan. Harvest is a common management tool used for centuries to limit populations of game species (Caughley 1977, Redmond 1986). Managing populations using harvest regulations allow certain sizes, numbers, sex, and species to be harvested, and often include open or closed seasons. Regulated hunting opportunity and harvest are cornerstones of the North American Model of Wildlife Conservation, which developed gradually following unregulated harvest of wildlife populations that often were at risk of overharvest or extinction (Geist et al. 2001). Since then, many populations have recovered and expanded to the point where harvest regulations are now often used to limit or even reduce populations of some species. In general, harvest regulations have been well established as an effective way to control animal populations in many aquatic and terrestrial systems and are broadly accepted among the hunting and fishing public. For example, harvest regulations have been established or adapted to reduce or control populations of feral hogs (Sus scrofa; Hanson et al. 2009), white-tailed deer (Odocoileus virginianus; Simard et al. 2013) and cougar (Puma concolor; Cooley et al. 2009), overabundant small black bass (Micropertus spp.; Isermann and Paukert 2010), northern pike (Esox lucius; Pierce 2010) or non-native species (Arlinghaus et al. 2016b). Harvest has also been employed as a tool for controlling populations of invasive species. However, in many cases invasive species are so overabundant that a substantial commitment to harvest is necessary, which may exceed recreational harvest capacity and require commercial harvest or an active lethal control program by management agencies. Often removal of invasive species is challenging because the ultimate goal may be to eliminate the entire population, which may require impractical efforts. For example, controlling Asian carp in the Illinois River may require harvest rates of at least 70% (Tsehaye et al. 2013), whereas in the Great Smoky Mountains, an annual harvest rate of 40% would be necessary to decrease feral hog populations (Salinas et al. 2015). Many invasive species are known to negatively impact native species and ecosystems; thus, eradication is an ideal outcome. However, there may be opportunity to use harvest to control populations of native (or non-native) species that have some value yet are still overabundant. In this chapter, we explore the process of using harvest to control overabundant populations that have some recreational value, provide two examples to control overabundant populations using harvest, and describe the challenges and effectiveness associated with these efforts and some of the unintended effects of using harvest to control populations.