Abundance Trends and Drivers of Change in Freshwater Fish Communities of the New River Basin
Sleezer, Logan John
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Habitat destruction/alteration and non-native species are widely considered the two most serious threats to biodiversity within freshwater ecosystems, which are among the most threatened in the world. I examined the effects of these factors, specifically focusing on land use and non-native species as drivers of abundance patterns of native fishes in the highly invaded and anthropogenically impacted New River basin (NRB) in the Appalachian region of the United States. In chapter 2, I examine current native and non-native species abundance patterns related to the highly variable land-use mosaic present across the NRB, with specific focus on the species-specific effects of intensive land-use practices (agriculture and urbanization) at varying spatial extents (upstream watershed, upstream riparian, and local riparian). In chapter 3, I investigate historical context of basin-wide and site-level abundance spread and decline of natives and non-natives in the upper and middle New River basin (UMNR) over the past 60+ years. Finally, in chapter 4, I partition the variation in native species abundance explained separately by land use and non-native species to determine which factor might be most influential in describing abundance distributions of UMNR native fishes over the past 20+ years. My results indicate widely varying responses of native species to various combinations of intensive land use and non-native species across contributing watersheds and widespread biotic homogenization and native species declines over the past 60+ years. These declines include reductions in unique communities and endemic species provided little consideration or protection under current conservation law. I suggest potential avenues for improvement of conservation actions to help preserve these unique species and communities based on their responses to various land-use and non-native species stressors. My study framework should be broadly applicable to other drainages and should provide opportunities for early identification of potential native species declines and the stressors that may be contributing to them.
General Audience Abstract
Freshwater fishes are experiencing world-wide declines that have the potential to cause major negative ecological and economic impacts. Two of the biggest contributors to fish declines are habitat destruction and non-native species introductions. I examined populations of numerous fish species in the New River basin (NRB) in the Appalachian region of the United States to identify declining native species and determine how intensive land use (one type of habitat destruction) and non-native species may be contributing to these trends. My results suggest that nearly half of the native species occurring in the NRB may be experiencing widespread reductions in abundance. As a result of these declines and the spread of a few common native and non-native species, fish communities across the NRB are becoming less unique over time. Land-use changes, such as agricultural and road development near streams, which contribute to increased soil erosion and run-off of silt and sand into streams, could be causing broad habitat changes that lead to diminished populations of sensitive species and overall local and regional fish diversity. While no single non-native species may be held responsible for all native fish species declines in the NRB, complex interactions, such as competition and predation, between many natives and non-natives altogether could be contributing to many native fish declines. Farmers and other landowners can help to prevent future fish declines by re-establishing natural vegetation, such as trees, along streambanks and implementing other practices, such as cattle fencing, that reduce the streambank and soil erosion that harms fish habitat. Other stakeholders, such as anglers, can help prevent future native fish declines by limiting introductions of additional non-native species. For example, these stakeholders could avoid releasing aquatic pets and live bait into NRB streams. These practices would help limit future negative impacts caused by non-native species.
- Masters Theses