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

Abstract

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 km2 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. © 2016 Society for Marine Mammalogy.