Introduction of non-native species is a primary threat to aquatic ecosystems and can negatively affect native biodiversity and ecosystem functions, often resulting in costly economic impacts. Non-native Seal Salamanders (Desmognathus monticola) represent an emerging threat to aquatic ecosystems in Arkansas. In 2003, an introduced population of D. monticola was discovered in Spavinaw Creek in the Ozark Highlands of extreme Northwest Arkansas. Subsequent genetic work traced the origins of this population to the Southern Appalachians, and speculated use of salamanders as fishing bait as the route of introduction (Bonett et al. 2007). The Ozark Highlands and Boston Mountains are a hotspot of aquatic biodiversity and have several endemic salamanders, but lack a native, large plethodontid stream salamander (Trauth 2004), thus providing suitable stream habitat for D. monticola that is free from natural controls in the form of interspecific competition and intraguild predation. We have been studying this introduced population for several years and recently conducted the first thorough assessment of their distribution and abundance (Bush et al. 2018). We found D. monticola throughout approximately 10 km of the creek’s headwaters, with an estimated density of 14.5 individuals/m2 (wet biomass of 50 g/m2) at one location. This abundance is among the highest reported for stream salamanders. We are currently extending this research to more fully understand the ecology of introduced D. monticola and their potential effects on native salamanders, invertebrate communities, and the stream ecosystem.