The acoustic detection of the Franciscana dolphin (Pontoporia blainvillei), in open sea off the coast of Argentina

The Franciscana dolphin (Pontoporia blainvillei) is facing significant threats in the Southwestern Atlantic Ocean, largely due to entanglement in artisanal fishing nets, which makes it the most threatened dolphin species in the region Its conservation calls for a standardised methodology that enables the detection and monitoring of dolphin populations on a longer temporal scale. This study represents the first acoustic monitoring of wild Franciscana dolphins in Argentina, focusing on understanding their diel patterns of activity and their relationship with environmental variables. Our findings show that Franciscana dolphin acoustic presence in summer in Chapadmalal (Argentina) is more frequent in January than in February and March and is influenced by the interaction between tide and wind direction. Specifically, at higher tide levels, wind direction has a reduced impact on dolphin detections. This interaction varies seasonally, with shifts observed in February and March. This research advances standardised methodologies for detecting and monitoring Franciscana dolphin populations, supporting efforts to improve their conservation.