Invasive lionfish dispersal between shallow- and deep-water habitats within coastal Floridian waters

Invasive lionfish threaten native fishes and ecosystem health in the Atlantic, Gulf of Mexico, and Caribbean. Controlling their spread and population growth can be difficult given their early maturity, high fecundity, a long larval dispersal period, and preference for structure. Mitigation efforts are further complicated by the existence of large and numerous deep water refugia. Despite the potential importance of these refugia, their connection with shallow water populations and their role in recruiting pelagic larvae is poorly understood. We examined the post-settlement dispersal patterns of invasive lionfish using otolith δ13C and δ18O stable isotope analysis and Bayesian stock mixture analysis. We find that there is settlement within both deep- and shallow-water habitats. It is estimated that 34.5% of the shallow-water population is composed of individuals that moved from deep-water habitat and into these shallow regions post-settlement. Only 4.1% of the deep-water population is composed of individuals that settled in shallow-water habitat before dispersing. These results demonstrate a link between deep and shallow habitats within the coastal waters of Florida, with the flow of individuals from deep to shallow water being the predominate dispersal direction of post-settlement individuals. We suggest that post-settlement dispersal can contribute to the invasion of new habitat and potentially hinder shallow-water removal efforts in currently colonized areas.