Population estimation of the bottlenose dolphin

宽吻海豚(Tursioptruncatus)一年四季都在日本九州Amakusa筑岛附近的水域中发现。最近，该水域的观测船数量有所增加。现在人们怀疑，他们接近海豚可能会对这种野生动物产生一些不良影响。本研究的目的是为了获取与保护和管理筑岛宽吻海豚种群相关的生态信息。海豚种群的数量通常只有一个。海豚群的活动方向与海岸线平行。其分布集中在距海岸1-2公里、水深小于20m的海域。发现其运动具有规律性的昼夜规律，即早晨在水域东部活动，接近中午停留在岛前，日落时向西移动，并尝试利用背鳍的缺口进行图像识别。总共确认了192人的身份。有些人每个赛季都有复视，有些人连续9个赛季复视。考虑到在经纬仪调查的所有日子都发现了这一种群，而附近水域又没有关于共同发现的信息，因此，出现在筑岛水域的海豚构成了一个常驻种群。按月划分的初步估计为201-323人(cv：11.4-22.9%)

The bottlenose dolphin (Tursiops truncatus) is found throughout the year in the waters near Tsujishima island, Amakusa, Kyushu, Japan. Recently number of watching boats have increased in the waters. It is now suspected that their approaching to the dolphins may some bad effects on this wild animal. The objective of this study is to obtain ecological information associated with conservation and management of the Tsujishima bottlenose dolphin population.Theodolite tracking was carried out on the hill of Tsujishima island. Number of the dolphin schools was commonly one. The dolphin school moved longitudinally in parallel with coast lines. Its occurrence concentrated in the waters off 1-2 km from the shore and of depth less than 20m. A regular diurnal pattern in its movement was recognized, that is, it moves in the eastern part of the waters in the morning, stays in front of the island near noon, and moves westward near sunset.Photo-identification was attempted using notches of the dorsal fin. A total of 192 individuals was identified. Some of them resighted in every season and some of them resighted continuously in 9 seasons. In consideration that the school was found on all the days of theodolite survey and that no information on common findings was available in adjacent waters, the dolphins occurring in the Tsujishima island waters constitute a resident population.Population size was estimated by a capturerecapture method. Preliminary estimates by month ranged 201-323 individuals (cv : 11.4-22.9%)