214
Different of the other species of the genus Stenella, the S. frontalis has preference for more coastal waters, habiting regions with depths varying between 20 and
961 m (Moreno et al. 2005) and is considered as the most common in the south and
Southeast Brazil (Zerbini et al. 2004). This pattern of distribution of the S. frontalis
is similar to one observed throughout the Southeastern coast of the United States
and Gulf of Mexico, where the species occurs in regions of depths between 20 and
200 m (Jefferson and Schiro 1997; Würsig et al. 2000).
The pygmy killer whale, Feresa attenuata, is one of the less studied dolphin species in the world because its pelagic habits. The observed sightings contribute to the
diversity of cetaceans in the study area. The fact of this species was observed near
to the coast could be a result of oceanographic features, mainly the narrow continental shelf or even to prevent any type of noise in oceanic waters, such as ongoing
seismic activity off Brazilian coast (Rossi-Santos et al. 2006b).
In general, F. attenuata is seen in small groups, with 50 individuals being more
typical (Carwardine et al. 2002; Bastida et al. 2007), what it corroborates with the
sightings of the work.
There are many records of strandings of Peponocephala electra for the northeast
of Brazil, including a massive strand of at least 240 individuals, in Itacaré (Lodi
et al. 1990). Sightings of the species are rare, with only one record reported until the
present (Zerbini et al. 1999).
Is common to see groups of 100–500 individuals (Carwardine et al. 2002; Bastida
et al. 2007). Our results bring information about smaller groups of P. electra. There
is another record about groups of 14 individuals for the Southeast Caribbean
(Watkins et al. 1997). Despite this similarity, in the Caribbean, the species was registered occurring in waters of 1200 m of depth (Watkins et al. 1997), what is different of the depth found in this work.
Anthropogenic factors as traffic of boats, activity of production of oil and gas
and seismic exploration can also influence the distribution of the dolphins (eg.,
Richardson et al. 1995). It is believed that the first influence on the cetacean distribution is probably the aggregation of prey species (Davis et al. 1998), which is
determinant in the occurrence, social organization, composition and group size of
dolphins (Wells et al. 1980).
8.5 Conclusions
There is a considerable difference between the spatial distribution for the three more
frequent species, where the T. truncatus if distributed for all coast, the S. guianensis
showed preference for coastal waters, the S. bredanensis is limited to two places of
the coast, Praia do Forte and Itacaré, making a great interval in the occurrence of the
species inside of the study area.
Differences in the selection of habitat among the species can reflect distinct habits of foraging strategies, and also can contribute for reduction of the competition
between species that occur in the same geographic area. In our work, according
M.S. de Carvalho et al.
Different of the other species of the genus Stenella, the S. frontalis has preference for more coastal waters, habiting regions with depths varying between 20 and
961 m (Moreno et al. 2005) and is considered as the most common in the south and
Southeast Brazil (Zerbini et al. 2004). This pattern of distribution of the S. frontalis
is similar to one observed throughout the Southeastern coast of the United States
and Gulf of Mexico, where the species occurs in regions of depths between 20 and
200 m (Jefferson and Schiro 1997; Würsig et al. 2000).
The pygmy killer whale, Feresa attenuata, is one of the less studied dolphin species in the world because its pelagic habits. The observed sightings contribute to the
diversity of cetaceans in the study area. The fact of this species was observed near
to the coast could be a result of oceanographic features, mainly the narrow continental shelf or even to prevent any type of noise in oceanic waters, such as ongoing
seismic activity off Brazilian coast (Rossi-Santos et al. 2006b).
In general, F. attenuata is seen in small groups, with 50 individuals being more
typical (Carwardine et al. 2002; Bastida et al. 2007), what it corroborates with the
sightings of the work.
There are many records of strandings of Peponocephala electra for the northeast
of Brazil, including a massive strand of at least 240 individuals, in Itacaré (Lodi
et al. 1990). Sightings of the species are rare, with only one record reported until the
present (Zerbini et al. 1999).
Is common to see groups of 100–500 individuals (Carwardine et al. 2002; Bastida
et al. 2007). Our results bring information about smaller groups of P. electra. There
is another record about groups of 14 individuals for the Southeast Caribbean
(Watkins et al. 1997). Despite this similarity, in the Caribbean, the species was registered occurring in waters of 1200 m of depth (Watkins et al. 1997), what is different of the depth found in this work.
Anthropogenic factors as traffic of boats, activity of production of oil and gas
and seismic exploration can also influence the distribution of the dolphins (eg.,
Richardson et al. 1995). It is believed that the first influence on the cetacean distribution is probably the aggregation of prey species (Davis et al. 1998), which is
determinant in the occurrence, social organization, composition and group size of
dolphins (Wells et al. 1980).
8.5 Conclusions
There is a considerable difference between the spatial distribution for the three more
frequent species, where the T. truncatus if distributed for all coast, the S. guianensis
showed preference for coastal waters, the S. bredanensis is limited to two places of
the coast, Praia do Forte and Itacaré, making a great interval in the occurrence of the
species inside of the study area.
Differences in the selection of habitat among the species can reflect distinct habits of foraging strategies, and also can contribute for reduction of the competition
between species that occur in the same geographic area. In our work, according
M.S. de Carvalho et al.