Climbing up the ladder: male reproductive behaviour changes with age in a long-lived fish

Abstract High reproductive performance is the key attribute of male fitness, especially due to high skew among males most animal species. Males long-lived iteroparous species have opportunities improve upon their previous attempts with increasing age. We collected individual-specific behaviour and age data on a cyprinid fish, asp ( Leuciscus aspius ), from 2015 2019. tested whether changed over time using unique dataset where individual was recorded yearly passive telemetry. Individual fish tracked one five seasons at least year after tagging. Fish were scored by measures quality (first arrival time, number visits spent in grounds, encountered proportion all adult fish). In general, improved first three metrics age, suggesting shift towards behaviours likely enhance success as individuals aged. A larger size tagging predictive earlier spawning ground subsequent years. Our study therefore demonstrates importance factor when considering potential Significance statement fitness. reproducing multiple times life this 5-year study, we large telemetry systems during reproduction. investigated age-related behavioural changes demonstrated improvement timing length stay repercussions for male’s output. emphasize old experienced population, which are often targeted selectively removed human-managed waters.