Biogeography of common dolphins (genus Delphinus) in the Southwestern Atlantic Ocean

TAVARES, M; MORENO BENITES I; SICILIANO, S; RODRÍGUEZ, D; DE OLIVEIRA SANTOS, M; LAILSON BRITO JR, J; FABIÁN, ME

Mammal Review

Wiley Blackwell

Lugar: Londres; Año: 2010 vol. 40 p. 40 - 64

0305-1838

1. The common dolphins (genus Delphinus) present one of most problematic taxonomies and complex distribution patterns among all cetaceans. Although the taxonomy and the distribution seem to have been clarified in the eastern North Pacific and Indo-Pacific Oceans, these questions are still unclear in the Southwestern Atlantic Ocean (SWA). 2. We reviewed data from strandings, incidental catches and sightings since 1922. Systematic surveys were conducted in five major areas. Twenty one natural history collections were examined to measure 135 skulls. 3. A total of 184 records of common dolphins were compiled. They apparently occur in three stocks in the SWA: one located in northern Brazil and two others from southeastern Brazil (~22ºS) to central Argentina (~42ºS). Two distinct patterns in habitat use by depth were observed: in southeastern Brazil, sightings were restricted to coastal waters, with depths ranging from 18 to 70 m. On the other hand, in the area that extends from southern Brazil to Central Argentina (from 28°S to 42°S), sightings were recorded in deeper waters, ranging from 71 m to 1,435 m, with the exception of occasional coastal sightings. The cranial analyses demonstrated that both short and long-beaked forms occur in the SWA. 4. In the SWA, Delphinus seems to occur associated to areas of higher productivity. One stock is associated with the productive waters discharged by the Amazon River and possibily with the coastal upwelling system off the coast of Venezuela, while the other stocks are correlated to the Cabo Frio upwelling system and the Subtropical Convergence. Our results indicate that the current taxonomy does not adequately reflect the amount of variation within the genus in the world.