Occupancy and detection of Wavyrayed Lampmussel (Lampsilis fasciola) in Ontario, Canada¹

Abstract

Freshwater mussels (Bivalvia: Unionidae) are the most imperilled taxon in Canada. To facilitate species recovery efforts, an understanding of species distribution and habitat that supports species persistence is needed. Detecting mussels presents unique challenges, however, requiring considerable effort due to their complex life-histories and widespread declines. Here, observations of the imperilled Wavyrayed Lampmussel (Lampsilis fasciola Rafinesque 1820) from the Grand and Thames rivers, Ontario, Canada were used to quantify species detection and occupancy probabilities, and the relationship between occupancy probability and substrate size. The best model for the data included a river-specific covariate for detection and an intercept model for occupancy. Detection probability of Wavyrayed Lampmussel was higher in the Grand River than the Thames River. Limited variation in substrate size measurements restricted occupancy modeling, but field measurements qualitatively aligned with previous habitat descriptions. Overall, knowledge of species detection and occupancy probabilities for Wavyrayed Lampmussel will not only enhance the understanding of species distribution and habitat associations, but also ensure that the response of the species to threats and recovery actions are captured.