Landscape-Level Predictors of Localized Extirpation in Bridle Shiner (Notropis bifrenatus)

Bridle shiner (Notropis bifrenatus) is apparently declining over most of its range and is currently listed as a species of concern in Connecticut.  Recent research indicated the apparent decline of bridle shiner in the state was in part due to changes in sampling gear used for statewide surveys.   Seining used 50 years ago was demonstrably more effective at capturing bridle shiner than the currently favored and more frequently used electrofishing gear.  The present study is a reevaluation of the species distribution in light of this recent finding.  We seined at all known historic sites in Connecticut and found that some populations once thought to be extirpated are in fact extant.  Nonetheless, bridle shiner have a sharply reduced range in Connecticut, in that the number of site occurrences has declined 60% over 50 years.  Using a GIS approach we identified landscape-scale habitat measures that were potential predictors of extirpation.  We investigated metrics associated with land cover change, such as impervious surfaces, and those indicative of habitat fragmentation and patch isolation using logistic regression.  Our results provide needed context on declines in this species and potential avenues for conservation actions.