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 ..., Data for individual fish captured in lakes or rivers. All information, including ages and strontium isotopic ratio, are included., , # A partially migratory salmonid diversifies and shifts its migratory life history during the transition from anadromous migration to adfluvial migration

**Description of the data**

**Data S1: information for all individuals**

no: Column number
Year: Year surveyed
date: Year/Month/Date surveyed
Location: Study sites
ID: ID for each specimen
fork length (mm): Fork length of fish
standard length (mm): Standard length of fish. NA = no data available
sex: Sex of fish. NA = no data available
riv_year: Age at migration. NA = no data available; unknown: the age could not be determined by scale analysis.
mig_year: Year of migration. NA = no data available; unknown: the age could not be determined by scale analysis.

**Sharing/Access information**
Please contact the corresponding author (Takuya Sato: [[e-mail]](mailto:[e-mail])) if you are interested in using the data.