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>.原始提供方：海梅·博利亚诺斯-希门尼斯（Jaime Bolaños-Jiménez） 数据集归属：海梅·博利亚诺斯-希门尼斯 摘要： 为评估委内瑞拉鲸类动物的实际生存现状，普罗丰纳（Profauna，委内瑞拉鱼类与野生动物服务局）正在委内瑞拉中部海岸阿拉瓜州开展为期两年的野外研究项目。本项目是获取基线信息以制定海洋哺乳动物保护与研究行动计划的第一步。截至目前，研究团队已于1996年10月至1997年6月间完成1次航空调查与24次船舶调查，在大陆架海域共记录到30次目击事件。各类目击的相对频率如下：大西洋斑海豚（*Stenella frontalis*）占50%，宽吻海豚（*Tursiops truncatus*）占17%，两种海豚的混合种群占10%，未识别海豚占17%，未识别鳁鲸科（Balaenopterid）鲸鱼占6%。 宽吻海豚的种群个体数为1至15头，大西洋斑海豚的种群个体数则为3头至300头以上。大西洋斑海豚表现出亲社会性行为：包括船首乘浪（bowriding）、护航以及围绕船只“嬉戏”，行为时长从数分钟至1小时以上不等。而宽吻海豚则极少表现出此类行为，多数时候相当胆小谨慎。 在水下观测到一群超过300头的大西洋斑海豚时，有25头个体进行船首乘浪并伴随船只航行；当船只在该区域绕行并减速时，它们会下潜至45至60英尺，绕行至船尾后再次进行船首乘浪。该行为会重复多次，且始终由同一亚群完成。在罕见的一次10头宽吻海豚船首乘浪的场景中，另一群大西洋斑海豚也加入其中，开始一同船首乘浪。 初步结果显示，研究区域沿岸的海豚种群全年多数时段均有分布，且可能存在每日沿海岸线向东或向西的移动模式。大西洋斑海豚在个体绝对数量与目击频率上均为该区域的优势物种。如渔民反映，后续研究将补充鲸鱼出现的季节性相关数据。本内容为DLAM 009项目的初步研究成果，该项目由阿拉瓜基金赛特（Fundacite Aragua）资助。