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Dolphins are mammalians that integrate the cetacean family. They can be generally found in the sea but there are some species that live in rivers. There are some 37 species of dolphins mapped in Brazil. Their life time is about 35 years and the period of gestation is 10 months. They can reach up to 3 meters in length. The most known, of long nose, are about 2 meters long. Dolphins are most known by their abilities of diving and jumping at the water level, wondering people. An important characteristic used for distinguishing different individuals is its dorsal fin. It has no bounds in its composition and its size varies from specie to specie. Most important, its shape varies for individuals of the same specie. Besides this shape peculiarity, the dorsal fin keeps marks made by natural attackers, as sharks and others, or even fights, that may also be used for distinguishing them. These features form a natural signature as a finger tip. Currently, there are several researches dealing with these animals in partially demarked environments in beaches or rivers. The objectives are such as behavioural studies between groups (Link, 2000), counting statistics, and others. One of the difficulties is the lack of an exact limit of the observed areas. Besides, there is also some difficulty due to human observing capability, which is somewhat avoided due to a constant presence of a same specie in a same region. Other known difficulty is the acquisition of dolphin images. Most species keeps some distance from boats and other aquatic vehicles or even they disappear to deep water. This makes hard the work of researchers who needs to observe a live data or data obtained from photos for posterior identification. The last is known as visual photoidentification and is often practiced by biologists. Photo-identification can give information about motion parameters and population dynamic (Mann, 2000). This method has being applied through the last three decades mainly in the Tursiops truncatus (bottlenose) dolphin specie. This method is also employed to identification of Orcinus Orca (most known as the killer wale) and other cetacean species (Defran, 1990; Flores and Mann, 2000). As the pictures are generally taken in different conditions (day, time, and weather), photoidentification through purely human observation may be subjected to errors and to human analyzer subjectivity. The population of Dolphins analyzed in the current work lives in a coastal region of Rio Grande do Norte state known as Dolphin Bay, to the south of Natal (state Capital), between the Tabatinga and Buzios beaches. The work proposal is to build a system able to extract efficient features from digital pictures and to use them for identification of dolphins. This is a challenge mainly because pictures are generally taken by biologists and |
