Report of the Working Group on Distribution and Behavior

Abstract

The known boundaries for the distribution of franciscana range from Itaunas (18o25’S, Espirito Santo State, Brazil) in the north (Siciliano, 1994), to the Golfo Nuevo (42o35’S, Chubut Province, Argentina) in the south (Crespo et al., 1998). There is no concrete evidence that the species exists outside these boundaries. However, the distribution appears to be fragmented along the Brazilian coast, above 27oS (Siciliano and Santos, 1994). There are two “gaps”, places where sightings, incidental mortality or other evidence of the species’ existence have not been documented, and where fishermen do not recognize it, which indicate that the species is absent or rare. These gaps occur in the southeastern Brazilian coast, between Ubatuba (23o20’S), Sao Paulo State, and Macae (22o25’S), Rio de Janeiro State, and between Barra de Itabapoana (21o18’S) and Regencia (19o40’S), Espirito Santo State. This fragmentation could be attributed to potentially limiting factors in the distribution, such as the impact of the freshwater discharge from the Paraiba and Doce Rivers in the southeast of Brazil, the very narrow continental shelf and the frequent presence of predators (i.e. killer whales, Orcinus orca, and sharks) (Siciliano, 2001). In Argentina, the known distribution is continuous, and the species has been documented all year along the entire coast of the Buenos Aires Province (Bordino et al., 1999).