Photoperiodic control of smoltification in anadromous salmonids
Smolting is the phenotypic transformation of juvenile salmonid fish from a freshwater resident phase (parr) to a seawater migratory phase (smolt).
The parr-smolt transformation (PST) encompasses several changes adaptive for life in seawater, of which the development of seawater osmotic tolerance is the most studied.
PST depends on seasonal timekeeping, and is initiated by declining photoperiods in the autumn prior to migration to sea, with completion of the process dependent on increasing photoperiods in the spring. The natural light-dependence of this process is of major economic importance because of its implications for aquaculture production processes.