Movement, Habitat Use and Detection Probability of Bridle Shiner Estimated by Patch Occupancy Modeling in a Connecticut Watershed

The bridle shiner (Notropis bifrenatus) is believed to have once been an important prey item throughout its native range; however, recent reports suggest populations have declined significantly and the species is now widely considered as imperiled. Habitats that are associated with this species are typically difficult to sample using traditional methods, making it unclear how much of the observed range reduction could be actual or perceived. My objectives were to estimate detection probability of bridle shiner, evaluate the importance of habitat on their distribution, and determine patterns of movement among habitat patches. I employed a repeated surveys design to estimate detection probability based on capture history and to draw inferences about sites where the species was never encountered. Bridle shiner were batch marked to evaluate among-patch movement distances and frequencies. Movement was infrequent and overall detection probability was high. Detectability was negatively associated with mean water velocity and positively associated with abundance. Occupied habitats tended to have higher springtime macrophyte cover, stable flows over time, and were connected by short distances to similar areas. Among occupied patches, those with shallower mean depths supported bridle shiner in high abundance later in the year, which may be an indication of habitat that is important for recruitment and survival. My findings suggest that false absences are not likely the cause of reported declines in Connecticut and that habitat degradation may be a leading cause of extirpations throughout the state