Informing Management of American Shad (Alosa sapidissima) in the Carolinas: Evaluating Novel Fish Passage Approaches and Acoustic Tracking Methods

Acoustic telemetry is a valuable tool for fisheries scientists to study the movements and migratory behaviors of aquatic organisms. A critical assumption of this method is that tagged fish exhibit similar behaviors and survival rates as their untagged counterparts. To investigate this, we conducted a 12-week laboratory study on adult American Shad (Alosa sapidissima) using gastroesophageal insertion of acoustic transmitters. We implanted 80 fish with dummy transmitters and monitored tag retention and survival. Our analysis, employing a mixed effects Cox’s proportional hazards model, revealed no significant differences in survival between tagged and control fish, regardless of sex. Additionally, reproductive development, assessed through gonadosomatic index (GSI) values and macroscopic gonad classification, was unaffected by tagging, and body condition remained consistent across groups. Overall, transmitter retention was high at 95%, with only two transmitters expelled. In a field application, we assessed fish passage solutions on the Cape Fear River, North Carolina, where mitigation efforts were implemented to facilitate the movement of anadromous species past three low-head dams (LDs). We tagged 100 American Shad with acoustic transmitters and monitored their passage from March to May in 2023 and 2024. Passage rates varied across LDs, with the modified nature-like fishway at LD1 showing 77% in 2023 and 80% in 2024. Environmental flows and conservation locking were crucial for passing fish at LD2 and LD3. Our findings indicate that effective passage solutions, including modified fishways and strategic water releases, are essential for supporting American Shad migration.