The bottlenose dolphin (Tursiops truncatus) is a small marine mammal of cosmopolitan habit.
In Brazil it occurs all over the coast. Although this dolphin is the most studied among
odontocetes, most dolphin studies come from the south of the country. In the northern region,
the evidence of occurrence of the species is mostly associated with strandings records. Thanks
to the active efforts of research groups in the region, the reality of species occurrence data has
been updated, especially data about the ecology of the living individual. The objective of this
study was to obtain information about the occurrence of individuals of T. truncatus species, as
well as data about their group size, group composition and distribution along the Amazonian
continental shelf (PCA) using visual monitoring. Twelve campaigns were carried out from
February 2018 to February 2019 under the Costa Norte Project, where the aquatic biota
monitoring activity was carried out along the Amazonian continental shelf (from Oiapoque -
AP to São Luís - MA). As soon as the bottlenose dolphin (Tursiops truncatus) was observed on
the surface, data such as number of individuals, group composition (between Adults and
young), observed behavior (such as displacement, feeding, socialization and respiration) and
georeferenced coordinates, were described in spreadsheets. During the twelve campaigns
carried out, 225 individuals were sighted throughout the PCA. The group size ranged from 2 to
20 individuals, with an average of 3.33 and fashion equal to 2. The group composition showed
that most sightings were adults (n = 201) and only 24 pups. The most observed behavior was
displacement (61.3%), followed by socialization (30.2%) and food (4.44%). Its distribution
along the PCA showed a possible hotspot pattern and a residence pattern, with individuals being
sighted all along the vessel's course. These results suggest that PCA is a zone with the
occurrence of T. truncatus throughout the year, in which individuals find in this region a suitable
range for their activities. Even with the information presented here, a long-term study of the
species off the north coast of Brazil is suggested. Therefore, in addition to knowledge about its
distribution in the PCA that will serve for further conservation of the species, the data will
contribute to the dissemination of data of the species in northern Brazil.
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