Pattern of Invasion of a Nonindigenous Cyprinid and Potential Shifts in Native Fish Assemblage Structure

Abstract

Invasive species increasingly threaten global biodiversity with faunal homogenizations and are of specific concern in the highly diverse aquatic systems of the Southeast United States. However, patterns of invasion and variables influencing invasion success remain poorly understood. This study had the unique opportunity to follow the introduction, establishment, and invasion processes of nonindigenous Weed Shiner (Notropis texanus, Family: Cyprinidae), and to investigate potential shifts in the native fish assemblage in Bear Creek, Alabama and Mississippi, USA, following introduction from the Mobile Basin via the Tennessee-Tombigbee Waterway. Weed Shiner’s invasion pattern, based on historical and contemporary fish assemblage surveys from 1998 to 2013, was established by GIS mapping. Shifts were evaluated using Jaccard and Morisita similarity indices and nonmetric multidimensional scaling ordination. Since first observed in Bear Creek in 2007, Weed Shiner rapidly expanded in range and abundance until 2012 when is range contracted and 2013 when abundances declined. Weed Shiner currently persists at the most human-impacted, downstream sites in Bear Creek. Despite the rapid proliferation of Weed Shiner 2007 – 2012, the native fish assemblage has not significantly changed. Rather, the native fish assemblage structure in Bear Creek is highly variable temporally and influenced largely by land-use in the watershed, most notably by high intensity development, mixed-hardwood forest cover and pine monoculture cover. Limiting future Weed Shiner impacts in the system and successful conservation of the Bear Creek fish assemblage will rely on managing land use changes and mitigating the effects of development in the watershed on the stream.