FISHERY ACTIVITY IMPACT ON THE SOTALIA POPULATIONS FROM THE AMAZON MOUTH - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 222

I NTRODUCTION
Sotalia guianensis , one of the smallest Delphinidae , is very common in the coastal
western Atlantic, where there are steady increases in human population growth rate and
population density along with those activities that support this growth. One factor addressed
in this chapter, fisheries, has been enhanced in the region to meet the demand of burgeoning
human populations and new developmental projects along the coast. There are potential
negative direct and indirect effects of fishing activities on marine life which make Sotalia
guianensis a highly vulnerable species in this region (Trujillo, 1992; Trujillo & Beltrán 1995;
Silva & Best 1996).
Although it is a species that is included in Annex I of the CITES, and classified by The
International Union for Conservation of Nature and Natural Resources (IUCN) as
―insufficient data‖, in addition to being protected by indigenous and fishermen communities'
traditions, and by specific regulations in almost every country within its distribution area, S.
guianensis is exposed to anthropogenic effects, which affects the stability of its populations.
A review conducted by conservation scientists of potentially harmful anthropogenic factors
suggested that two factors, new dam construction and bycatches by the coastal drift net
fisheries were of principle concern. On account of these findings the continuous monitoring
of those interactions became a priority, and a key element for defining the status of
populations and providing for conservation mechanisms (Northridge, 1985).
Several fishing accounts recorded along the Brazilian coast stated that bycatches of this
species, collected via waiting and drafting's gillnets, is often accompanied by other cetacean
species such as Pontoporia blainvillei (Lodi & Capistrano, 1990). Fishing villages in the
northeastern and southeastern Brazil, are using these types of nets where the bycatch of S.
guianensis , has been recorded without bias to the fish harvested or fishing effort (Lodi &
Capistrano, 1990; Barros & Teixeira, 1994).
In southern Brazil, where the fishing-dolphin interactions are better monitored and
known, bycatch of S. guianensis is low and Pontoporia blainvillei has become the most
vulnerable species (Perrin et al., 1994; Pinedo, 1994 a, b ). In the state of Pará, Siciliano (1994)
mentions the villages of Algodoal, Marudá, Salinópolis, Bay of Marajó and Vigia as the
places where the fisheries show the largest interaction with S. guianensis, with adults being
the most vulnerable group . These dolphins are also harpooned and then used as shark bait
(Barros, 1991; Borobia et al., 1991). It is common for fishermen to remove the genital organs
and the eyes from the dolphins to be sold in the market as love charms and witchcraft devices
at the Ver-o-Peso market in Belém; the teeth are sold as ornaments.
In Central American countries there are small artisan fisheries using 30 to 2,000 m long
nets with mesh sizes of 4 cm up to 40 cm in which several species of cetaceans including S.
guianensis are caught (Perrin et al, . 1994). Bycatches of S. guianensis in Nicaragua,
Honduras, Colombia, Surinam and French Guyana have been recorded by Vidal et al . (1994).