Assessing movement patterns of the highly invasive western mosquitofish (Gambusia affinis)

The western mosquitofish is among the top 100 invaders in the world, yet it continues to be introduced globally for mosquito control. This study investigates the movement patterns of the western mosquitofish and develops movement predictions for their continued invasion. We combined mark-recapture experiments, meta-analysis of previous movement studies and application of an existing fish movement model involving fish morphology, stream order and time to advance knowledge of western mosquitofish secondary spread. Our results reveal that small-scale and short-term movements by invasive western mosquitofish are predictable using existing statistical models. However, movement over larger scales and longer timelines was consistently underpredicted by existing models, suggesting our current understanding of invasion capacity by western mosquitofish is limited. We used sensitivity and optimization methods to identify parameter adjustments that make existing statistical models relevant for broader-scale invasions, and we illustrate the improved inference gained from this approach by modelling future spread of a recently invaded region. Our results provide quantitative estimates of western mosquitofish invasion across a range of contexts and can direct conservation and management actions aimed at improving invasion monitoring, predicting risk of secondary spread and understanding invasion dynamics at multiple spatiotemporal scales.