A Novel eDNA-Based Approach for the Monitoring and Management of the Endangered Beluga (Huso huso, Linnaeus, 1758) and Adriatic (Acipenser naccarii, Bonaparte, 1836) Sturgeon

Beluga sturgeon (Huso huso Linnaeus, 1758, acipenseridae) and Adriatic sturgeon (Acipenser naccarii, Bonaparte, 1836, acipenseridae) within the Po River basin have been recently assessed for the IUCN Red List of Threatened Species and were found to be Extinct in the Wild and Critically Endangered, respectively. Significant declines in both species’ abundance have spurred major research efforts and management actions in recent decades. Recently, specific actions have been conducted to recover habitat connectivity through projects of river defragmentation and reintroduction plans have been implemented for both sturgeon species. To manage effective conservation efforts, knowledge of a species’ distribution and abundance is critical, especially for adult sturgeon that are able to move hundreds of kilometers away from release sites. Here, two new quantitative PCR (qPCR) assays to detect beluga sturgeon and Adriatic sturgeon environmental DNA (eDNA) in water samples have been developed with the goal of providing an alternative method to monitor their presence. Two Taqman-based assays targeting the mitochondrial cytochrome b region were developed and showed no amplification of other related and co-occurring fishes. A mesocosm within the Ticino Park on the Ticino River (a main tributary of the Po River), where both species are bred, was used to develop and validate the assays. The LOQ for H. huso assay corresponded to Ct = 41 (7.33 × 107 DNA counts/µL of reaction) and for A. naccarrii it was Ct = 37 (2.23 × 1016 DNA counts/µL of reaction). Additionally, water samples were taken from the discard drainage, which flows directly into the Ticino River, testing positive detection of eDNA within a distance of up to 2 km. Overall, the results suggested that the two assays developed in this study could represent a promising new tool for monitoring both beluga and Adriatic sturgeon.