Size-driven parr-smolt transformation in masu salmon (Oncorhynchus masou).

Anadromous salmonids exhibit partial migration, where some individuals within a population migrate down to the ocean through complex interactions between body size and photoperiod. This study aimed to integrate the ontogenetic and seasonal patterns of smoltification, a series of changes for future marine life, in a strain of masu salmon (Oncorhynchus masou). Spring smoltification, as evidenced by the activation of gill Na,K-ATPase (NKA), was induced during winter under an advanced photoperiod.