Development and Use of an Environmental DNA Tool to Monitor Recovery of the Critically Endangered Smalltooth Sawfish, Pristis pectinata, in the Northwest Atlantic

• Main Author: Lehman, Ryan N
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2020
• Subjects: Conservation; Endangered Species; Ray; Droplet Digital™ PCR; Species recovery; eDNA; Genetics; Indian; Northwest Atlantic
• Online Access: https://aquila.usm.edu/masters_theses/769; https://aquila.usm.edu/context/masters_theses/article/1821/viewcontent/auto_convert.pdf

The Critically Endangered Smalltooth Sawfish, Pristis pectinata, was once common in the tropical and subtropical waters of the Atlantic Ocean; however, following global declines in range and abundance over the past century, individuals were restricted to the waters of south and southwest Florida (SWFL) by about the 1980’s. Recently, public encounter reports have emerged in historically occupied habitats in United States waters, suggesting individuals are present in, or re-occupying, these areas, although the status of P. pectinata outside of SWFL is not currently well understood. Targeted environmental DNA (eDNA) surveys were chosen to assess the occurrence of P. pectinata in these formerly inhabited waters due to the rapid, cost-effective, and non-invasive advantages of this technique over traditional survey methods for P. pectinata like gill nets. This research developed and validated a species-specific eDNA assay capable of targeting P. pectinata DNA in water samples at concentrations as low as 0.08 copies/μL using Droplet Digital™ PCR. This assay was then used in three formerly occupied estuaries in the western Atlantic that had recent, verified encounter reports: Tampa Bay and the Indian River Lagoon (IRL), Florida, and the Mississippi Sound, Mississippi. Pristis pectinata DNA was detected in water samples collected from the IRL in 2018 and 2019, and the Mississippi Sound in 2018, indicating at least one individual was present in the vicinity near the time of sample collection. These results provide another line of evidence for potential re-occupation; however, long-term, comprehensive eDNA surveys are needed to help foster future recovery.