Stock identification study on elasmobranchs

利用形态学、生态学和遗传学特征对板鳃类，特别是三种鲨鱼进行了种群鉴定研究。关于星斑角鲨Mustelus manazo，根据从7个地点收集的1，514个标本进行了广泛的种群鉴定研究。典型相关分析发现，不同地区之间的形态差异。在年龄和生长方面也观察到地理差异，表现出向北方地区生长和寿命增加的趋势。出生时身长也有类似的趋势。体长和成熟龄随纬度的增加而增加。幼仔数随亲鱼体长增加而增加，相同体长下，东京湾幼仔数最少，台湾最多。然而，青森的生殖周期似乎与其他地方大不相同。饮食习惯也揭示了地理变化，表现出胃内容物重量占总重量的比例向南增加。因此，据推测，在日本周围至少有五个星点角鲨种群。对来自世界7个地区的133只角鲨进行了形态学和遗传学研究。在不同地区的皮肤密齿、胸鳍和尾鳍的形状上观察到了显著差异，导致了三个群体的分离，即地中海、南非、日本和澳大利亚。在遗传学上，有三个群体，日本，澳大利亚和南非。由于这些原因，物种复合体被分为四组，日本，澳大利亚，地中海和南非。关于大洋白鳍鲨Carcharhinus longimanus，首次在太平洋阐明了其年龄、生长和繁殖，获得了该鲨鱼种群的基本信息。

Stock identification studies on elasmobranchs, particularly three species of sharks, were conducted using morphological, ecological, and genetic characters. Regarding starspotted dogfish Mustelus manazo, extensive study on stock identification was carried out based upon 1,514 specimens collected from seven localities. Morphological differences between localities were detected by canonical correlation analysis. There were also observed geographical differences in age and growth, showing trend of increase of growth and longevity toward the northern locality. The similar trend was also observed in lenngth at birth. Length and age at maturity showed a tendency of increase with latitude. Litter size showed an increase with parent length and the smallest number in Tokyo Bay at the same length whereas largest in Taiwan. However, the reproductive cycle in Aomori seemed to be quite different from other localities. Food habits also revealed geographical variations, demonstrating an increase in the ratio of stomach content weight to total weight toward south. As a result, it is suggested that there are at least five stocks of the starspotted dogfish around Japan. Regarding shornose spurdog Squalus megalops, paopulation studies were conducted using morphological and gentic characters based upon 133 specimens collected from seven localities in the world. Significant differences were observed in shape of dermal denticles and pectoral and caudal fins between localities, resulting in the separation of three groups, the Mediterranean, South Africa, and Japan and Australia. Genetically, three groups, Japan, Australia and South Africa were distinguished. For these reasons, the species complex was divided into four groups, Japan, Australia, the Mediterranean and South Africa. Regarding the oceanic whitetip shark Carcharhinus longimanus, age, growth and reproduction were elucidated in the Pacific Ocean for the first time and fundamental information on stocks of the shark was obtained.