486
1991), current speed (Irvine et al. 1981) and bottom topography (Selzer and Payne
1988; Cañadas et al. 2002; Ingram and Rogan 2002). Environmental parameters are
considered indirect measures because they influence primarily prey distribution,
which in turn affects dolphin spatial and behavioral patterns (Wells et al. 1980;
Shane et al. 1986; Selzer and Payne 1988; Baumgartner 1997; Acevedo-Gutiérrez
and Parker 2000; Hastie et al. 2004).
Both species show an aggregated pattern of distribution with core areas, similar
to that of other coastal dolphins such as Tursiops truncatus (Würsig and Würsig
1979; Ingram and Rogan 2002), Souza chinensis (Karczmarski et al. 2000),
Lagenorhynchus obscurus (Würsig and Würsig 1980), and Lagenorhynchus acutus
(Selzer and Payne 1988). The area occupied by both species has substantially
reduced in the last 20 years. Although the species distribution strongly overlap,
there is no overlap of core areas (Cremer 2007).
Guiana dolphins were recorded in the innermost area of the bay between 1997
and 1999, including the Palmital channel and the harbor inlet (Cremer 2000). The
harbor inlet in São Francisco do Sul was intensively used by Guiana dolphins,
mainly for hunting and feeding (Cremer et al. 2009). Dolphins in this area have been
observed using the ships as a barrier to trap fish prey. However, in 2000 the harbor
was enlarged and underwent repairs required the use of dredges, pile-drivers, and
other heavy machinery, causing intense disturbance in the area. Guiana dolphins
were rarely seen in the São Francisco do Sul vicinity from 2000 to the 2006, and
were not found at all in the harbor inlet (Cremer et al. 2004, 2009). Seasonal changes
in distribution have been analyzed in recent years, and revealed the use of a larger
area in winter and a smaller one in the summer. Guiana dolphin core areas are
located central and south of the islands, and do not change throughout the year
(Fig. 17.9).
A similar trend was observed for franciscana dolphins, however changes in distribution encompassed smaller areas. In 2006, the population was well distributed
along the central region of the bay. Since then, the species has preferentially occupied the north coast of the bay, and greatly reduced habitat area within the bay
(Cremer and Simões-Lopes 2005; Sartori 2014) (Fig. 17.10).
Patterns of dolphin habitat use in Babitonga Bay vary by daily tidal cycles, but in
different ways for the two species. Both species utilize areas closer to the continental shore at the end of flood tide (Paitach et al. 2017). This is the period when tidal
flats overflow, causing fish to migrate to these important feeding areas (Reis-Filho
et al. 2011). Dolphins use these areas opportunistically, as fish are more vulnerable
to predation in these locations (Reis-Filho et al. 2011).
Franciscanas move toward the mouth of the bay during ebb tide and away from
the mouth during flood tide, following the flow of the current (Paitach et al. 2017).
This behavior is similar to that of franciscanas in Anegada Bay (Bordino 2002).
Guiana dolphins do not exhibit strong patterns in relation to tidal current, typically
occupying inner areas at early ebb stage and remaining near the mouth of the bay in
late flood stage. Although a counter-current foraging strategy has already been
described for T. truncatus (Shane 1990), movement following the direction of
M.J. Cremer et al.
1991), current speed (Irvine et al. 1981) and bottom topography (Selzer and Payne
1988; Cañadas et al. 2002; Ingram and Rogan 2002). Environmental parameters are
considered indirect measures because they influence primarily prey distribution,
which in turn affects dolphin spatial and behavioral patterns (Wells et al. 1980;
Shane et al. 1986; Selzer and Payne 1988; Baumgartner 1997; Acevedo-Gutiérrez
and Parker 2000; Hastie et al. 2004).
Both species show an aggregated pattern of distribution with core areas, similar
to that of other coastal dolphins such as Tursiops truncatus (Würsig and Würsig
1979; Ingram and Rogan 2002), Souza chinensis (Karczmarski et al. 2000),
Lagenorhynchus obscurus (Würsig and Würsig 1980), and Lagenorhynchus acutus
(Selzer and Payne 1988). The area occupied by both species has substantially
reduced in the last 20 years. Although the species distribution strongly overlap,
there is no overlap of core areas (Cremer 2007).
Guiana dolphins were recorded in the innermost area of the bay between 1997
and 1999, including the Palmital channel and the harbor inlet (Cremer 2000). The
harbor inlet in São Francisco do Sul was intensively used by Guiana dolphins,
mainly for hunting and feeding (Cremer et al. 2009). Dolphins in this area have been
observed using the ships as a barrier to trap fish prey. However, in 2000 the harbor
was enlarged and underwent repairs required the use of dredges, pile-drivers, and
other heavy machinery, causing intense disturbance in the area. Guiana dolphins
were rarely seen in the São Francisco do Sul vicinity from 2000 to the 2006, and
were not found at all in the harbor inlet (Cremer et al. 2004, 2009). Seasonal changes
in distribution have been analyzed in recent years, and revealed the use of a larger
area in winter and a smaller one in the summer. Guiana dolphin core areas are
located central and south of the islands, and do not change throughout the year
(Fig. 17.9).
A similar trend was observed for franciscana dolphins, however changes in distribution encompassed smaller areas. In 2006, the population was well distributed
along the central region of the bay. Since then, the species has preferentially occupied the north coast of the bay, and greatly reduced habitat area within the bay
(Cremer and Simões-Lopes 2005; Sartori 2014) (Fig. 17.10).
Patterns of dolphin habitat use in Babitonga Bay vary by daily tidal cycles, but in
different ways for the two species. Both species utilize areas closer to the continental shore at the end of flood tide (Paitach et al. 2017). This is the period when tidal
flats overflow, causing fish to migrate to these important feeding areas (Reis-Filho
et al. 2011). Dolphins use these areas opportunistically, as fish are more vulnerable
to predation in these locations (Reis-Filho et al. 2011).
Franciscanas move toward the mouth of the bay during ebb tide and away from
the mouth during flood tide, following the flow of the current (Paitach et al. 2017).
This behavior is similar to that of franciscanas in Anegada Bay (Bordino 2002).
Guiana dolphins do not exhibit strong patterns in relation to tidal current, typically
occupying inner areas at early ebb stage and remaining near the mouth of the bay in
late flood stage. Although a counter-current foraging strategy has already been
described for T. truncatus (Shane 1990), movement following the direction of
M.J. Cremer et al.