期刊名称：Memoirs of the Graduate School of Fisheries Sciences, Hokkaido University
印刷版ISSN：1346-3306
出版年度：1997
卷号：44
期号：1
页码：39-46
出版社：Hokkaido University
摘要：Migration is a fundamental biological response to adversity. Salmon move progressivelyfrom one habitat to another as a habitat ceases to satisfy their changing needs. Hatching fromthe egg into the gravel redd, emerging from the redd onto the stream bed, moving away toestablish a feeding territory, moving downstream to deeper water over winter, and finallyemigrating from freshwater to sea - all these are abandonments of habitats once they can nolonger satisfy the salmons! needs. The downstream migration of smolting fish is interpretedchiefly as the eviction of an organism which is losing freshwater adaptation, involvingphysiological, behavioral and morphological components. Final passage through the estuaryis complicated by rhythmical tidal current reversal and salinity increase, and temperatureconditions modify the die I pattern of activity. Because the evolutionarily refined timing ofarrival in the sea is critical for smolting salmon at anyone river mouth, the construction ofestuarine barrages poses serious problems for the maintenance of viable salmon populationsin those rivers.
