Photo-identification is a commonly used research tool used to identify individual dolphins and other animals. The camera “captures” an image of the animal whenever it is sighted, based on the amount of times it is “captured” a statistical method called “mark – recapture” is used to estimate the size of the population in a defined area. During an encounter with dolphins, researchers photograph marks (such as cuts or scars) on the back of the animals. Markings located on the trailing edge of the dorsal fin (the fin on the back) are particularly important for individual recognition. These marks occur naturally and are like a fingerprint, unique to each dolphin. The “capture” of these fins on photographs provides an indirect and non-invasive method to record the presence of a specific dolphin in a sighting. Photos of identified individuals are then stored in a catalogue. The ADP catalogue currently consists of over 2250 individuals, each labelled with a name or a code-number. Approximately 180 of these individuals are permanently resident animals in the Lošinj area – the Lošinj community of dolphins. Based on the same methods, our estimates suggest that around 400 individuals inhabit the Vis archipelago with further 300 being residents of the north Dalmatian waters. The rest are only occasionally present in these waters. Data obtained using this method creates a detailed picture of the state of the dolphin community – their use of this habitat assessment of birth and mortality rates, as well as their social relations.