3 RESULTS

3.1 Seasonal migration timing of Sakhalin taimen

In 2018, a total of 105 PIT-tagged Sakhalin taimen spawners returned to the Karibetsu River, including 90 fish tagged that year. In 2019, 76 tagged spawners returned, of which 73 had also returned in 2018 (i.e. consecutive repeat spawners). During the period of upstream migration, water temperature increased monotonically, while water level varied more stochastically but decreased substantially by the time spawners arrived at Site L (Fig. S1).

3.2 Between-year consistency in migration timing

The chronological order of individual Sakhalin taimen arriving or departing during each MS was remarkably consistent between 2018 and 2019 as evidenced by an apparent tendency of lines connecting the same individuals in these two years to be parallel to one another (Fig. 2).