Mark‐recapture abundance estimate of tucuxi dolphins ( Sotalia fluviatilis ) in a lake system of the Central Amazon

The tucuxi ( Sotalia fluviatilis ) is a small dolphin endemic to the Amazon River basin. Because the abundance and trends are currently unknown for the species, this study aimed to estimate its abundance in a lake system of the Central Amazon. A total of 10 two‐day sampling periods were carried out from March to June of 2013 throughout a 13.5 km 2 area in the Mamirauá Reserve. In the 104 encounters with the species, a minimum number of 389 dolphins were sighted and photographed, which allowed the positive identification of 49 individuals. Mark‐recapture models were used to estimate an abundance of 119 individuals (95% CI = 105–150) (corrected for the proportion of identifiable individuals). This is the first estimation of S. fluviatilis abundance using mark‐recapture analyses and, together with the photo‐id catalog made available, provides a useful reference for future studies regarding tucuxi dolphins.