2008 Fiscal Year Final Research Report

"The compact, freshwater migrations" for the general mechanisms of the fish migrations

Research Project

Project/Area Number	19570057
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Morphology/Structure
Research Institution	Okayama University
Principal Investigator	SAKAMOTO Tatsuya Okayama University, 大学院・自然科学研究科, 教授 (10294480)
Project Period (FY)	2007 – 2008
Keywords	回遊 / 環境 / ホルモン / 適応 / 保全 / 行動 / 国際研究者交流 / アメリカ合衆国:デンマーク
Research Abstract	We have observed that kissing loach and some other freshwater fishes migrate from the main stream of rivers to spawn in flood areas. These flood areas are unstable and ephemeral, however, they contain few aquatic predators and a large amount of food suitable for the development of embryos/juveniles. The present study provides the first evidence that the spawning migration of kissing loach is stimulated by rainfall and the subsequent rise in water level, as well as the new moon. Since similar observations have been reported for downstream migrations of salmonids, these stimuli may serve as general cues for migrations of fishes in rivers. Furthermore, the spawning of kissing loach is rigidly limited spacio-temporally after the formation of flood areas. Recently we have successfully demonstrated that changes in water quality directly induce migration and spawning behavior, suggesting some particular odoriferous substances may be the environmental proximate factors.