Testing passive dispersal as the key mechanism for lionfish invasion in the Mediterranean Sea using Lagrangian particle tracking

The expansion of lionfish Pterois miles across the Mediterranean Sea since its introduction via the Suez Canal has been rapid, but the mechanisms by which the expansion occurred have not been fully tested. By using a series of Lagrangian particle tracking simulations and high-resolution hydrodynamic models, we tested the hypothesis that passive dispersal of larvae could explain the east to west expansion of lionfish. By sequentially modelling the annual dispersal of larvae, from the first observation in Lebanon in 2012 and then modelling dispersal of larval from the simulated settlement sites, we showed that passive dispersal driven by ocean currents largely explained the observed expansion of lionfish until 2020. The spread of lionfish was likely restricted by environmental conditions when the population reached the central Mediterranean and the particle tracking simulations diverged from observations. The results emphasize the potential contribution of computational models in understanding the dispersal of non-indigenous and range expanding species in response to changing environmental conditions, identifying high risk areas, and guiding targeted surveillance, early detection, and informing management strategies for such species. Given that many non-indigenous species in the Mediterranean are introduced through a consistent pathway (the Suez Canal), the incorporation of interdisciplinary approaches and high-resolution biophysical models can provide fundamental knowledge for management action prioritization.