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coastal and riverine populations. Therefore,
Sotalia fluviatilis
is the first delphinid living
exclusively in freshwater.
S. fluviatilis
is endemic of the Amazon River and its main tributaries, from Brazil to
Colombia, Ecuador and Peru (da Silva & Best, 1996; Flores, 2002). The Amazon River basin
has been experiencing a steep increase in human activities in the last decades, most of them
potentially harmful to the Amazon river dolphins. Several anthropogenic threats have been
identified (ex. direct and indirect catch, building of dams, habitat loss and degradation, heavy-
metal contamination - Best and da Silva, 1989), but their effects on
S. fluviatilis
populations
remain unknown (IBAMA, 2001; Reeves et al., 2003). Those potential threats, combined with
the newly found endemism of
S. fluviatilis
, may jeopardize its persistence.
River dolphins are the most endangered cetaceans, because they share their endemic,
restricted habitat with increasing human populations and are therefore exposed to several
direct and indirect human-related threats (Reeves et al., 2003). For that reason, they have been
granted special conservation status. The newly found endemism of
S. fluviatilis
implies that
its conservation status should be reassessed, and it also
should be included in the river
dolphin category for conservation purposes.
The molecular identification of
Sotalia
species also led to an important discovery:
dolphin-derived products, illegally sold in the Brazilian Amazon as love charms, do not
belong to the red boto (
Inia geoffrensis
), as advertised by sellers. Instead, all samples that had
actually been obtained from dolphins belonged to the marine
S. guianensis
(Cunha & Solé-
Cava, 2007; Gravena et al., 2008; Sholl et al., 2008).
S. guianensis
amulets were detected not
only in Belém (Pará state, at the Amazon estuary) but in Manaus and Porto Velho, despite the
availability of botos and of
S. fluviatilis
in those areas. In one market (Ver-o-peso of Porto
Velho, Rondônia), 90% of the eyeballs sold were in fact from pig or sheep (Gravena et al.,
2008). The assessment of the impact of this illegal activity depended on the identification of
the targeted species.
Now that
S. guianensis
has been recognized as possibly the only species
currently used, authorities can act on the sources of charms, which are likely to be the
Amazon estuary and adjacent Pará and Amapá coasts.
S. guianensis
has been intentionally
caught in those areas to be used as shark bait (Pinedo, 1985) - a single boat had 83 specimens
on board (footage done by IBAMA and broadcasted by a Brazilian television network on
07/16/2007). Dolphin charms may originate both from by-catch from legal fisheries, and as a
second commodity of the illegal bait catch.
Molecular Ecology
Molecular markers have been successfully employed to investigate other aspects of the
biology of
Sotalia
, especially their population structure and social behaviour. Although
studies on
Sotalia
dolphins are still in course, they promise to reveal important data for the
conservation of those species.
Population Structure and Phylogeography
Phylogeography is a field of research concerned with the evolutionary and demographic
processes that shaped the genealogical lineages within or between closely related species
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