Identifying ontogenetic shifts in primary energy pathways of invasive red lionfish, Pterois volitans, in the Florida Keys via stable isotope and otolith analysis

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Emily E. Shallow, Cassandra Glaspie and Michael J. Polito, Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA

Background/Question/Methods
The invasive red lionfish, Pterois volitans, has been shown to considerably reduce reef biomass via predation and competition in non-native ranges. Primary maintenance of lionfish is through human removal (e.g., culling), which does not sufficiently control the population due to deep-water spawning, recolonization of recently culled reefs, and ontogenetic migrations to mesophotic waters. Here, we investigate the primary energy pathways and ontogeny of lionfish in the Florida Keys via otolith and stable isotope (δ13C & δ15N) analysis to better understand their role in the trophic food web and find if age impacts isotopic composition. Additionally, we will examine isotopic overlap between lionfish and native reef predators to assess competition. Lionfish (n=48) and other community representatives were collected from a mosaic of habitats in the Florida Keys (i.e., mangroves, seagrass beds, and coral reefs) in August 2020.
Results/Conclusions
Preliminary findings suggest lionfish on shallow reefs obtain their basal carbon values from different sources than lionfish at greater depths. Furthermore, assuming length serves as a proxy for age, lionfish in the Florida Keys may not exhibit ontogenetic migration to deeper waters. Finally, lionfish show extensive isotopic overlap with native reef fish, indicating that the extent of competition may be underestimated. To further investigate our objectives, a Bayesian mixing model will be used to estimate the proportional contribution of each source to the energy pathway of lionfish. Additionally, we will assess community isotopic niche space using δ13C & δ15N to gain insight on the community structure. A better understanding of which habitats contribute to the basal carbon transfer and ontogeny of lionfish in the Florida Key’s ecosystem could lead to improved management strategies that effectively mitigate the impact of lionfish on the local community.