Assessing the potential for red tide (Karenia brevis) algal bloom impacts on Atlantic tarpon (Megalops atlanticus) along the southwestern coast of Florida

This study investigated the potential effects of red tide events (blooms of the toxin-producing dinoflagellate, Karenia brevis) on Atlantic tarpon (Megalops atlanticus), a long-lived migratory game fish, along the southwestern coast of Florida. In this region, red tides have long been associated with mass mortality events of marine organisms and other deleterious effects on coastal ecosystems. To estimate the impacts of red tide on tarpon and the recreational fishery they support, we used a mixed-methods approach that combined multiple data sources including fish kill data, local ecological knowledge (LEK) interviews, angler catch logs, and acoustic telemetry. Our results suggested tarpon are somewhat tolerant to red tide blooms; but, when blooms did overlap with tarpon peak abundance and became dense and large, tarpon were reported to leave the affected area, suffered mortality, or both. Furthermore, in recent years, LEK data suggested an increase in the persistence and overlap of red tide blooms with peak tarpon abundance that coincided with their spawning season. In contrast, using acoustic telemetry data, we did not detect any pattern in tarpon presence during red tide events, further suggesting that tarpon may be adaptive to the effects of red tide. Finally to evaluate monitoring methods, data quality, and collection, we used a strengths, weaknesses, opportunities, and threats analysis and found all could be improved through increased engagement with LEK and collaboration among researchers. Ultimately, combining multiple data sources helped elucidate how red tide exposure influences tarpon and the recreational fishery that targets them.