All dolphins are different and most can be recognised from photographs showing natural markings, such as scars, colour patterns or irregularities in the shape of their dorsal fins. Identification from photographs, or photo ID is a simple, but powerful technique to study dolphins. Once a dolphin has been identified, researchers can give it a name (or a number) and include its pictures into photo ID catalogues.

Thereafter, every time the dolphin is photographed, scientists can record the location of the dolphin, the time when it was seen, and other relevant information such as its size, physical condition or reproductive state. The data gathered from photo ID can be used for estimations of abundance and in many different studies, including migrations and movements, social structure and life histories.