Cetacean and sea turtle sightings in Gabon

Original provider:
Marijke de Boer

Dataset credits:
Marijke N. de Boer

Abstract:
Information on cetaceans and marine turtles off Gabon in tropical West Africa was collected during boat-based surveys carried out between 7 March and 7 August 2009. Thirteen cetacean species were positively identified comprising two baleen whale species, one sperm whale species and ten species of delphinid. Bryde’s whale (Balaenoptera brydei) and humpback whale (Megaptera novaeangliae) were the most frequently encountered species. Cetaceans were found throughout a range of sea surface temperature between 20.5˚C and 27.5˚C and a wide range of depths with the majority of effort and sightings occurring seaward of the shelf break. Of particular interest from the study were the following: (1) Gabonese waters have a broad cetacean diversity, especially with a large and diversified delphinid community in the northern part of the study area; (2) the variations in oceanographic conditions within Gabonese waters are likely to result in a temporal variation in species composition; (3) the sightings of Atlantic spotted dolphin (Stenella frontalis) are the first at-sea sightings confirmed for these waters, although not unexpected given their distribution and abundant presence in surrounding waters; and (4) the poorly known Clymene dolphin (Stenella clymene) was sighted on four occasions in deep oceanic waters and was the most abundant cetacean. These are the first confirmed records of Clymene dolphins in Gabonese waters.

原始提供方：
玛丽克·德·博尔（Marijke de Boer）

数据集署名：
玛丽克·N·德·博尔（Marijke N. de Boer）

摘要：
2009年3月7日至8月7日期间开展的乘船调查中，研究人员收集了西非热带加蓬海域鲸类与海龟的相关数据。本次调查共确凿识别出13种鲸类，涵盖2种须鲸、1种抹香鲸以及10种海豚科（delphinid）物种。其中布氏鲸（Balaenoptera brydei）与座头鲸（Megaptera novaeangliae）为本次调查中最常被观测到的物种。
鲸类的观测覆盖了20.5℃至27.5℃的海表温度区间与多样水深环境，绝大多数调查作业与目击记录均发生在陆架坡折外侧海域。
本研究的核心发现如下：（1）加蓬海域拥有丰富的鲸类多样性，尤其在研究区域北部存在规模庞大、类群多样的海豚科群落；（2）加蓬海域内的海洋水文条件变化，可能导致物种组成随时间产生波动；（3）大西洋斑海豚（Stenella frontalis）的目击记录为加蓬海域首次经确认的海上观测结果，尽管结合其分布范围与周边海域的种群丰度，这类目击并非意料之外；（4）此前鲜为人知的克莱门海豚（Stenella clymene）在深海大洋水域被4次目击，且为本次调查中数量最多的鲸类类群，这也是加蓬海域内克莱门海豚的首次经确认的记录。