Simulated effects of Indo-Pacific lionfish (Pterois volitans and P. miles) invasions on parrotfish (Scaridae family) populations on coral reefs in the Caribbean

Background/Question/Methods: The introduction of invasive species in marine environments is rare but detrimental to the existence of native species. The Indo-Pacific lionfish species (Pterois volitans and P. miles) recently has invaded coral reefs across the Atlantic and Caribbean at an alarming rate.These invaders pose a harmful threat to the stability of the marine ecosystem as they are capable of dramatically altering community composition and structure. One keystone species currently being affected by the lionfish invasion is the parrotfish (Family Scaridae). The parrotfish plays a vital role in the stabilization of coral reef ecosystems by preventing a phase shift from coral to macro-algal dominated reefs. We proposed to study the dynamics of parrotfish populations in response to the lionfish invasion in the Caribbean. Our objective is to understand the potential effects lionfish may have on native fish population, and how they could possibly pose a threat to the stability of the marine ecosystem. We reviewed the literature to obtain recent demographic parameters for both the lionfish and parrotfish, developed an age-/stage-structured population dynamics model for each species, and then integrated the two models in order to quantify the potential effects of lionfish on parrotfish population dynamics on coral reefs in the Caribbean. A monthly-time step STELLA® model ran for 120 months, with an initial recruitment density of 40 fish per hectare for each species.

Results/Conclusions: After 120 months post-invasion, projections of the lionfish display a population increase, and projections of the parrotfish display a population decrease. Our data demonstrated the lionfish population has direct effects on the parrotfish recruitment with a negative effect of 3.3 per squared kilometer. This lead the parrotfish population to a decline after 98 months. In conclusion, our results imply that an increase of the Indo-Pacific lionfish population could drive the native parrotfish populations to extinction. The decline of native reef species, such those of the scaridae family, coupled with the increasing lionfish densities, suggest that the lionfish has the potential to exacerbate the declining trend recently noted of the Caribbean coral-reefs. We recommend an extensive lionfish alleviation to prevent any further damage to any species contributing to one of the most diverse ecosystems in the planet.