Personality predicts dispersal and settlement in a novel habitat-a mesocosm experiment.

Individual phenotypes strongly affect dispersal. Yet studying the relationship between dispersal tendencies and personality under ecologically relevant conditions is challenging, especially in fish. Laboratory studies lack environmental complexity and scale, while field-based approaches are often unfeasible. We here mimicked dispersal events in fish; encompassing all 3 phases of dispersal (departure, transience, settlement) in a large experimental mesocosm containing breeding sites. Using 3-spined sticklebacks (Gasterosteus aculeatus) tagged with 'Passive Integrated Transponders' (PIT tags), we remotely monitored proxies of dispersal of 2 cohorts, each consisting of 40 individuals of known activity and aggressiveness scores, continuously over 2 wk. We tested whether personality variation explained differences in departure timing, transience movements, settlement success and spatial distribution along the environmental gradient. We found that more active/aggressive individuals dispersed quicker in the mesocosm, spent more time on territories and collected more eggs. However, we did not detect strong phenotype-environment correlations. Our findings emphasize the potential role of personality-dependent dispersal in population dynamics, with specific behavioral types driving dispersal and settlement success. Our mesocosm setup provides unique insights into the dispersal dynamics in a system where detailed observations across all dispersal stages are rare and difficult to obtain. Despite limitations, behavioral experiments in mesocosms serve as a valuable bridge between laboratory and natural systems.