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

María Gabriela Silva-Hernández, Universidad Central de Venezuela

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.

This data is the result of a study carried out between March 2006 and January 2007 in response of the inclusion of whale watching (WW) activities into the priorities of three national programs of the Ministry of Science and Technology and Fundacite Aragua. We expect that WW activities will soon be successful at a commercial level, so we decided to generate data on the biological and ecological aspects of the three cetacean species presents in the coast of Aragua (Stenella frontalis, Tursiops truncatus and Balaenoptera edeni). This information will provide a basis for future comparisons about population aspects as well as responsible management of this activity in the region as well as in the country.

Total effort for the whole reasearch: 4294 min

Overview

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Attributes in dataset

Attribute (table column)	Description
sighting	Sighting No. for each species
latitude	in decimal degree
longitude	in decimal degree
obs_date	Date of observation
obs_time	Time of the observation (local time zone)
effort	Effort in minutes
duration	Sighting duration in minutes
obs_count	Group size
beaufort	Beaufort sea state
cloudiness	Cloudiness
sp_obs	Species observed
sp_tsn	ITIS taxonomic serial number
geom	Geometry field added by OBIS-SEAMAP
oid	Unique ID number (generated by OBIS-SEAMAP)