Observation and photo-identification of Lahille's bottlenose dolphins in the Lagoa dos Patos in Brazil with our research boat Charlotte. These trips take place regularly and are very important for the assessment of the population in the Lagoa dos Patos. The photo-ID method is based on the distinguishing feature of the dolphins' dorsal fin, as this is different for each animal. This allows individual animals to be identified and the total population to be estimated. With the help of a database, the animals can be recognized and sightings registered.