Ornate Invaders: The movements of invasive lionfish (Pterois volitans) in Floridian coastal waters

Background/Question/Methods: In the 1990s, lionfish (Pterois volitans) were introduced to Floridian waters and have since spread rapidly throughout the Caribbean, damaging the native trophic structure. They inhabit every Atlantic habitat within their thermal threshold, are usually slow-moving, and are site-specific (on the timescale of weeks). Due to the difficulties associated with tracking smaller, marine organisms we know little about the invasion mechanisms, how or if they migrate between habitats, or if the invasion has been facilitated mostly by settlement. We apply stable isotope analysis of ¹³C and ¹⁸O to lionfish otoliths sampled from a variety of depths and habitats along the Gulf coast of Florida and the Florida Keys. By sampling the otolith core and the outer rim, we create a profile of movement between the individual’s settlement location and its residence when caught. With this, we analyze how frequently they migrate away from certain depths, what proportion are site specific, and what habitat do they tend to migrate towards.

Results/Conclusions: Our results contradict the previous understanding that all lionfish are highly site-specific through their lifetimes. In shallower regions along the Gulf of Mexico, between 75-100% of individuals exhibit evidence of having settled deeper and moved into shallower depths. At depths between 150ft-250ft, only between 0-37% exhibit any evidence of migration away from their settlement habitat. In this region, the continental shelf slopes off gradually, leaving a large expanse of habitat over which the fish can move. In contrast, individuals from shallow, flat seagrass beds in the Keys are more site specific with only 16% of individuals migrating into the area from deeper habitat. These preliminary results are some of the first to look at settlement patterns of the invasive lionfish. This research is the first to use stable isotope analysis to examine the settlement and migratory behavior of P. volitans within its invaded range and provides critical information to lionfish management efforts in regards to developing specific, environment-appropriate control strategies.