Landscape factors predict local extirpation in an imperilled minnow species, the bridle shiner (Notropis bifrenatus)

Abstract

Abstract Local extirpation events are often poorly documented and the causes are not well understood. A case in point is the bridle shiner (Notropis bifrenatus), a cyprinid that is declining and carries various conservation listings over most of its range. Recent research suggested that the apparent decline of the bridle shiner in the state of Connecticut may be in part an artefact of changes in survey methods: seining has been replaced by electrofishing, which is less efficient in bridle shiner habitat. The present study included a re‐evaluation of the distribution of the species in light of this recent finding. Historical sites in Connecticut were seined, and it was found that nine populations once thought to be extirpated were in fact extant. Nonetheless, bridle shiner occurrences have declined by 60% over 50 years. Potential correlates of extirpation, such as landscape and habitat fragmentation metrics, were identified using geospatial tools. Through an information‐theoretic approach, models were constructed to investigate the relative contribution of land use and habitat fragmentation to the extirpation of the bridle shiner. Land use had greater support as a correlate of the decline, and the current bridle shiner distribution in Connecticut could be explained by areas of high forest cover and low impervious cover. It is hypothesized that the adverse impacts of land use on the bridle shiner are attributable to its ecological specialization on submerged vegetation, notwithstanding its otherwise broad physiochemical tolerance. These results provide needed context on the decline of this species and provide potential avenues for conservation actions. This research emphasizes the impacts that land alterations can have on freshwater species and the importance of accurately characterizing extirpation events.