著者

東 幹夫

出版者

日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.23, no.6, pp.255-265, 1973-12-20

被引用文献数

10

---

The main events experienced by the fish belonging to each population are schematically summarized in Fig. 1., basing on all the results given in the previous reports. Concerning the variations in the body form and the numbers of fin rays found in each population, it was suggested that these characters in question would be influenced by the environmental factors differently according to the developmental stages of the fish concerned. Through the morphological comparisons on the degree of the ossification of the skulls as well as the ring formation of the scals of the sea-run and the landlocked Ayu-fish, it was confirmed that the latter would be the form which suppressed their growth to some extent. However, the landlocked form can be considered to have relatively higher fecundity comparing with the sea-run form, because of their earlier spawning period, the ova with smaller diameter and more numerous in number. The dwarfism, and the early maturation of the present landlocked form coincided with the general tendencies already pointed out by many previous authors who studied several other species of landlocked fishes. Some considerations were made on the relation between the intra-species differentiation of the present species and the geological history of the lake.