Structure of Population in Larvae and Juveniles of Ayu-Fish, with Comments on Possibility of Survival of the Lake Biwa Population in Coastal Waters.

香鱼幼鱼和幼鱼的种群结构，以及对琵琶湖沿岸水域种群生存可能性的评论。

• 批准号: 60560194
• 负责人: MOCHIZUKI Kenji
• 金额: $ 1.15万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60560194/
• 关键词: Plecoglossus altivelis; Structure of Population; Survival; Morphology; Formation of Borns; 日令

The present study intend to discriminate population of ayu-fish, Plecoglossus altivelis, originated from the Lake Biwa population which was released in rivers from Japanese river populations of the fish , and then to examine structure of populations in coastal waters. At first I examined morphologically larvae and juveniles of the two populations which were reared under similar conditions to find any differences that the two were discriminated from each other. Comparison of 15 morphological characters between the two shows that they are different from each other in 9 characters , but the results could not show which population each individual was belonged to. I collected larvae and juveniles in the sea near Kumano River, and morphological characters of them were compared with those of the reared populations. I could not find any differences morphologically between the wild and the reared river populations, but the wild was different from the reared Lake Biwa population in three characters. The results may imply that many of the wild samples were belonged to river population. Size of the reared river samples when formation of most cartilages and bones of them were started is bigger than that of the reared Biwa Lake samples. Examination of daily-ring of the wild samples shows existence of some individuals which were hatched in the middle-late September though number of them were few. The date were corresponded to those of fishes originated the Biwa Lake population. Therefore the present results imply that fishes originated the Biwa Lake population are able to survive in sea waters, and fishes originated from the Biwa Lake population should be discriminated from the river population in biological studies. The present study will be progressed to examine structure of wild population in seas based on the results mentioned above.

本研究旨在区分江河放流的琵琶湖种群和日本江水种群，进而考察近岸水域的种群结构。首先，我检查了在相似条件下饲养的两个种群的幼体和幼体的形态，以找出两者之间的区别。对两者15个形态性状的比较表明，它们在9个性状上存在差异，但不能反映出每个个体属于哪个群体。采集熊野江附近海域的仔稚鱼，并将其形态特征与养殖种群的形态特征进行比较。我找不到野生种群和饲养的河流种群在形态上的任何差异，但野生种群和养殖的琵琶湖种群在三个特征上是不同的。这一结果可能表明，许多野生样品属于河流种群。大多数软骨和骨骼开始形成时，饲养的河样比碧洼湖的饲养样的大小。对野生样品的日轮观察表明，9月中下旬孵化出的个体数量较少，但仍有部分个体存在。这些数据与起源于琵琶湖种群的鱼类的日期相一致。因此，目前的结果表明，起源于碧洼湖种群的鱼类能够在海水中生存，生物学研究中应区分源自碧洼湖种群的鱼类和来自河流种群的鱼类。本研究将在上述结果的基础上，进一步研究海洋野生种群的结构。