Harbour Porpoise Surveys 2008

A survey of harbour porpoises (Phocoena phocoena) was carried out at five sites (North County Dublin, Dublin bay, Cork coast, Roaringwater bay cSAC and Galway bay) to derive density and abundance estimates. Single platform line-transect surveys were carried out on six days at each site between July and September 2008. Distance sampling was used to derive g(0), which is the density of harbour porpoises on the track of the vessel. Abundance estimates were calculated using the track-line as the sample and the sighting as the observation. During 28 survey days a total of 354 track-lines were surveyed for a total distance of nearly 20,000 km in seastate ≤2. From the 269 sightings of a total of 496 individual harbour porpoise were recorded. There were 13 sightings with a total of 171 common dolphins (Delphinus delphis), eight sightings of single minke whales (Balaenoptera acutoratrata) and one sighting of 20 bottlenose dolphins (Tursiops truncatus). Five sightings with a total of 18 dolphins were not identified to species level.本研究于5个调查站点（北都柏林郡、都柏林湾、科克海岸、咆哮水湾特别保护区（Roaringwater bay cSAC）以及戈尔韦湾）开展港湾鼠海豚（Phocoena phocoena）调查，以获取其种群密度与丰度估计值。单平台线路样线调查于2008年7月至9月期间，在每个站点开展为期6天的作业。本研究采用距离抽样法估算g(0)，即船舶航迹线上的港湾鼠海豚种群密度。以航线路线作为抽样单元、目击记录作为观测样本，计算得到种群丰度估计值。 在总计28个调查日内，共完成354条样线的调查作业，有效调查总航程近20000公里，调查海况等级均≤2级。本次调查共记录到269次目击事件，涉及496头次港湾鼠海豚个体；其中13次目击事件共记录171头普通海豚（Delphinus delphis），8次目击事件均为单独的小须鲸（Balaenoptera acutoratrata），另有1次目击事件记录到20头宽吻海豚（Tursiops truncatus）。另有5次目击事件共18头海豚未能鉴定至物种水平。