Population ecology of the finless porpoise

通过对长崎附近沿海沃茨的江豚（Neophocaena phocaenoides）进行飞机照片分析、标本检查、飞机和船只的观察调查，对江豚种群的生态参数进行了估算。体长估计为0.7至2.2米。根据这些照片，估计有明海峡和立番湾的种群数量超过800只。根据航空目击调查，这一种群的另一个估计是3093个个体。在长崎附近的沿海沃茨，主要分布在有明湾、立花湾和大村湾。有明湾中部的密度估计为1.31-1.60只/km^2。平均学校规模为1.7人。该物种出生时身长80厘米，5岁时可长至140厘米。女性在6-9岁时达到性成熟。在长崎附近的分娩是从秋天到春天。一种描述了随着年龄和性二型性的发展。另一个试图根据头骨形态的地理差异来识别种群。该物种在4年前达到头骨成熟。多数颅骨性状未见两性异形。我们认为，在中崎附近的沿海沃茨存在两个种群，即有明湾立花湾种群和大村湾种群。

This project aimed to estimate the ecological parameters of the finless porpoise (Neophocaena phocaenoides) populations in the coastal waters near Nagasaki by analysing photos taken from an airplane, examining specimens, and sighting surveys from the plane and boats.A total of photos for 46 individuals were taken. Estimates of body length ranged from 0.7 to 2.2m. Using these photos, the population size in Ariake Sound and Tachiban Bay was estimated to be more than 800 individuals. From airo sighting surveys, another estimate for this population was 3093 individuals.A paper was published on distribution and seasonal density evaluated from the boat sighting surveys. In the coastal waters near Nagasaki, the species is distributed mainly in Ariake Sound, Tachibana Bay and Omura Bay. Density was estimated 1.31-1.60 individuals/km^2 in the middle part of Ariake Sound. The mean school size was 1.7 individualsA paper was publised on age, growth and reproduction. The species is born at length of 80 cm and grows up to 140 cm at age of 5 years old. Females attain sexual maturity at ages of 6-9 years. Parturition near Nagasaki is from autumn spring.Two papers were published on morphology of skeltons. One describes development with age and sexual dimorphism. The other attempted to identify stocks based on geographical difference in the skull morphology. This species attains cranial maturity by 4 years. Sexual dimorphism was not detectable in most of cranial characters. We suggested two stocks exist in the coastal waters near Nakasaki, that is, Ariake Sound-Tachibana Bay stock and Omura Bay stock.