Grant-in-Aid for Co-operative Research (A).
|Research Institution||Faculty of Fisheries, Hokkaido University|
GOTO Akira Hokkaido University, Faculty of Fisheries, Associate professor, 水産学部, 助教授 (30111165)
前川 光司 水産庁, 中央水産研究所, 室長
YAMAUCHI Kohei Hokkaido Univ., Fac. Fish., Associate professor, 水産学部, 助教授 (10109514)
TSUKAMOTO Katsumi Tokyo Univ., Ocean Res. Inst., Associate professor, 海洋研究所, 助教授 (10090474)
東 幹夫 長崎大学, 教育学部, 教授 (10039430)
MIZUNO Nobuhiko Ehime University, Fac. Science, Professor, 理学部, 教授 (70030319)
NUMACHI Kenichi Tokyo University, Ocean Research Inst., Professor, 海洋研究所, 教授 (30013569)
MAEKAWA Koji National Res. Inst. of Fisheries Science, Section leader
|Project Fiscal Year
1990 – 1992
Completed(Fiscal Year 1992)
|Budget Amount *help
¥18,900,000 (Direct Cost : ¥18,900,000)
Fiscal Year 1992 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1991 : ¥6,800,000 (Direct Cost : ¥6,800,000)
Fiscal Year 1990 : ¥10,200,000 (Direct Cost : ¥10,200,000)
|Keywords||Pattern of migration / Land-locking / Seawater adaptability / Heterochrony / Genetic differentiation / Reproductive strategy / Polypatric speciation / Evolutionary model / 回遊様式 / 河川湖沼陸封 / 海水適応能 / 個体発生変異 / 遺伝的分化 / 繁殖戦略 / 多所的種分化 / 進化モデル / 通し回遊魚 / 生活史変異 / 進化生態学|
In the present co-operative research project, physiological, biochemical genetical and ecological studies were carried out for 3 years to understand the mode od migration and life-history characteristics of Japanese diadromous fishes, the physiological mechanisms for adapting to freshwater or seawater environments, and the relationships between land-locking and speciation in diadromous fishes. The important results obtained by this research were listed below.
1) The amphidromous gobiid larvae are drifted by the flow in the upper courses of the river in daytime, while their daytime-drifting halt the migration in a pool of low flow rate. The variation in the diel periodicity of their migration can be explained by the interaction between behavioral reactions of embryos and environmental factors along the river courses.
2) During smoltification, masu salmon (Oncorhynchus masou) develop seawater adaptability as manifested in an increase in gill NA+, K+- ATPase activity. It is likely that this
rise in gill NA+, K+- ATPase activity is directly or indirectly pituitary dependent.
3) The spawning area of the Japanese eel was firstly determined to be in the North Equatorial Current west of the Mariana Islands, at a salinity front near 15 N, 140 E.
4) The morphological observations on the life-history characters of 2 land-locked gobiid species and the land-locked populations of threespined stickleback suggest that progenetic or neotenic heterochrony plays an important role of their adaptation to and evolution to the freshwater environments.
5) The type-assortative mating which was observed between the lake-run type and the river-resident type of white-spotted charr (Salvelinus leucomaenus) in the artificial lake, the Lake Arimine, suggests that the assortative mating in salmonids may play an important role not only in the maintenance of their life-history polymorphism, but also in their land-locking.
6) In many cases, the speciation of diadromous fishes which has occurred according to their land-locking can be explained by the hypothesis of polypatric and parallel speciation proposed by Goto (1987, 1990). Less