Current status of cetaceans in Aragua, Venezuela

Original provider:
Jaime Bolaños-Jiménez

Dataset credits:
Jaime Bolaños-Jiménez

Abstract:
As part of an effort to assess the actual status of the Venezuelan cetaceans, Profauna (the Venezuela Fish and Wildlife Service) is conducting a two-year field research project on the State of Aragua, central coast of Venezuela. It is the first step to get baseline information to devise an action plan for the conservation and research of marine mammals. So far, one flight and 24 boat surveys have been made between October 1996 and June, 1997. During this period, 30 sightings were recorded over the continental shelf. Relative frequencies were as follows: 50% Atlantic spotted dolphins (<i>Stenella frontalis</i>), 17% bottlenose dolphins (<i>Tursiops truncatus</i>), 10% mixed aggregations of these two species, 17% unidentified dolphins and 6% unidentified (Balaenopterid) whales. Group size for <i>Tursiops truncatus</i> ranged from 1-15 individuals and from three to more than 300 for <i>S. frontalis</i>. Spotted dolphins showed a sociable behavior by bowriding, escorting and 'playing' around the boat from only a few minutes to more than one hour. Bottlenose dolphins, on the other hand, very seldom showed this behavior, being rather shy most of the time. While watching a school of more that 300 spotted dolphins underwater, 25 animals bowrode and escorted the boat; as the boat reduced speed while circling the area they dived to 45-60 feet, looping back to the stern of the boat and then bowrode again. This behavior was displayed several times and was always made by the same subgroup. In one of the rare occasions when 10 <i>Tursiops</i> were bowriding, another school of <i>S. frontalis</i> joined them and started bowriding too. Preliminary results suggest the presence of coastal populations of dolphins along the study area during most of the year and, possibly, daily easterly or westerly movements (parallel to the coastline). <i>Stenella frontalis</i> is the most abundant species both in absolute numbers and sighting frequency. Further research will provide information about seasonality of whales presence, as claimed by fishermen. These are preliminary results of Project DLAM 009, funded by <a href=http:/www.fundacite.arg.gov.ve>Fundacite Aragua</a>.