Raw data from: A partially migratory salmonid diversifies and shifts its migratory life history during the transition from anadromous to adfluvial migration

Migration strategy requires complex life-history decisions, and how its
variation can increase or decrease during migration to novel environments
is fundamentally important for population persistence and adaptation for
migratory animals. An anadromous form of red-spotted masu salmon exhibited
almost only one sea migratory pattern probably due to high migration costs
in its southernmost habitat range of anadromous salmonids. Contrary to
this, we here found that the masu salmon have increased their migratory
patterns when they migrate to freshwater lakes (i.e., adfluvial
migration). Specifically, adfluvial migrants spent 1–3 years in lakes
whereas anadromous migrants are known to spend only half a year at sea. In
addition, adfluvial migrants returned to the river to reproduce after
maturation (called, mature run), whereas all anadromous migrants did so
before maturation (premature run). The diversification of the years of
migration and the shift in return-migration timing were only found in deep
lakes, where migrants can continue migrating in the favour of the cold
water of lakes. The present study demonstrated that a migratory salmonid
extensively diversified and shifted its migratory life history, often
requiring complex adjustments in life history traits with a genetic basis,
in novel environments.