Individual variation in spawning migration timing in a salmonid fish—exploring roles of environmental and social cues

Describing and explaining patterns of individual animal behaviors in situ, and their repeatability over the annual cycle, is an emerging field in ecology owing largely to advances in tagging technology. We describe individual movements of adult Sakhalin taimen, Parahucho perryi, an endangered salmonid fish, in the headwaters of a river in northern Japan during the spring spawning season over two years. Migration timing, separated into stages prior to, during, and following the spawning period, was found to be more consistent and repeatable for females than males. We hypothesized that the observed coordinated movement within seasons, and repeatability in migration timing across seasons, could result from 1) individual-specific responsiveness resulting from endogenous, biological traits that are mediated by environmental factors, or 2) social interactions among comigrating individuals. We found that water temperature and water level experienced by fish near the river mouth approximately a..., , R Markdown codes uploaded can be viewed and executed by using RStudio software.