Surgical tagging of <scp>Atlantic</scp> mackerel ( <i>Scomber scombrus</i> ): electroanaesthesia and survival in captivity and the field

Electroanaesthesia using electric fish handling gloves induced rapid and reversible sedation of Atlantic mackerel (Scomber scombrus) during surgical tagging without observable adverse effects on behaviour or tag retention. In the laboratory, survival analyses revealed that longer handling times and smaller body sizes significantly reduced survival rates. Particularly, most mortalities were associated with visible skin lesions and signs of infection, likely resulting from initial capture, transport stress and sensitivity to captivity. Wound assessments showed that surviving mackerel generally exhibited fully healed or minorly red incision sites, indicative of promising wound healing post-surgical tagging. Field trials using refined methods, including minimized handling and optimal capture methods, yielded a 92% survival rate, with only 4 of 50 fish classified as post-tagging mortalities based on acoustic telemetry detections. Statistical analyses confirmed significantly higher survival rates in the field compared to the laboratory. Outcomes from both settings informed the establishment of best tagging practices for Atlantic mackerel, providing a framework for improving fish welfare and enhancing the reliability of biotelemetry studies for this species.