Abundance and distribution of cetaceans in the state of Aragua, Venezuela

Original provider:
María Gabriela Silva-Hernández, Universidad Central de Venezuela

Dataset credits:
María Gabriela Silva-Hernández, Universidad Central de Venezuela

Abstract:
There is updated information on abundance and distribution of cetaceans in the central coast of Venezuela, where is needed baseline information in order to manage dolphin-watching activities. Between March 2006-January 2007, 28 surveys were made aboard small boats, powered with outboard engines, totaling 71.5 h of effort. The presence of Atlantic spotted (Stenella frontalis), bottlenose (Tursiops truncatus) dolphins and Bryde´s whales (Balaenoptera edeni) was confirmed. Cetaceans were found on 71.4% of the surveys. Relative abundance, expressed as number of individuals found per Km of transect line and hour of survey effort were 6 (± S.D. 12) and 26 (±S.D. 42), respectively, for S. frontalis and 1 (± S.D. 1) and 3 (±S.D. 2), respectively, for T. truncatus. Group size ranged from 6-400 individuals (mean 120 ± S.D. 119) and from 1-20 individuals (mean 8 ±S.D 7) for S. frontalis and, T. truncatus respectively. Some level of differentiation in habitat preference for these two species was found, with bottlenose dolphins preferring coastal waters over the 100m isobath, and Atlantic spotted dolphins preferring deeper waters around the 200m contour. Balaenopterid whales were found in March 2006, probably a cow-calf pair, Balaenoptera sp., and in October 2006, adult B. edeni.