Morphometric Scale Shape Variation of the Invasive Red Lionfish, Pterois volitans

Geometric morphometrics is a common tool that quantifies shape variation and has been used to explore morphological changes over ontogeny and investigate evolutionary relationships. Lionfishes are suction feeders that have cycloid scales. Cycloid scales in bony fishes are smooth, overlapping structures that have been hypothesized to serve multiple functions such as protection and streamlining the fish for efficient locomotion. Lionfish undulate their soft dorsal, anal, and caudal fins to move slowly through the water column, near the substrate. In this study we examined invasive lionfish, Pterois volitans, collected from public fishing derbies on the eastern coast of Florida. We used 2D geometric morphometrics to investigate lionfish scale variation along the length of the body from three regions (anterior, middle, caudal), and between sexes. We placed eight landmarks using anatomical loci on sixty scales from twenty specimens similar in size (TL = 170mm - 230mm). We hypothesized to observe significant scale shape variation among body regions and we expected to see shape variation between sexes, as males exhibit more aggressive behavior during mating. Lionfish showed significant shape differences among all regions (anterior, middle, and caudal), with scales being more elongated near the caudal fin. We also observed statistically significant shape differences between male and female scales. Specifically, females have wider scales in the middle body region and males have wider scales near the caudal fin. Overall, this study reveals more information about the morphology and sexual dimorphic traits of lionfish using unconventional specimen collection methods (public lionfish derbies). When conducting research on invasive species, we emphasize the importance of utilizing public events sponsored by state and local organizations, which are already engaging the public to significantly reduce population sizes.