Distribution of endangered Speckled Dace (Rhinichthys osculus) in British Columbia, Canada, based on environmental DNA metabarcoding – 12S dataset

The speckled dace (Rhinichthys osculus) is a small freshwater minnow listed as Endangered under Canada’s Species at Risk Act. In Canada, the species is restricted to the Kettle River watershed in south-central British Columbia and is geographically isolated from populations in the United States by Cascade Falls. Threats to speckled dace include low water flow conditions, habitat degradation, climate change, and threats posed by aquatic invasive species (AIS). Critical habitat for speckled dace is delineated as 2.4 km sections of the West Kettle, Kettle, and Granby rivers, starting at the species’ northernmost documented occurrence and extending downstream; however, evidence suggests this does not accurately reflect the species’ distribution. We used 12S environmental DNA (eDNA) metabarcoding with species assignments using a custom reference DNA sequence database to assess the distribution of speckled dace in the Kettle River above Cascade Falls. eDNA detection of speckled dace was consistently strong across filter replicates and markers at sites of known occupancy and was observed at two sites north of its currently described range. We also detected three invasive fish species with little or no records of occurrence in the sampled region, which warrant further investigation to confirm or refute. Overall, findings suggest that speckled dace occupy habitat beyond the existing upper boundary of their documented range in the Kettle River and co-occur with multiple AIS.[This dataset was processed using the GBIF Metabarcoding Data Toolkit.]