Trophic niche overlap & increasing populations of a nonnative invader in the coastal Everglades

Abstract

Abstract The Florida Everglades is a critically important, but highly threatened ecosystem that is becoming increasingly susceptible to the invasion of non-native species. This study investigated the ecological role of the invasive peacock eel (Macrognathus siamensis) within this ecosystem using 19 years of electrofishing data. We investigated the population trends of peacock eels at the marsh-mangrove ecotone of the Shark River Estuary, emphasizing the environmental factors contributing to their abundance and the potential interactions they may have with native fish assemblages and coastal food webs. We used stable isotope analysis to provide insights into the basal resource contribution to peacock eels and hypervolume analysis methods to determine peacock eel niche size and overlap with native species. Results of this study found that peacock ell abundance has rapidly increased, and their populations are strongly affected by hydroclimatic regimes—with warmer water temperatures and greater marsh inundation periods explaining greater abundance. We found that the trophic niche of peacock eels, though significantly smaller in volume, overlaps 98.8% with native sunfishes (Lepomis spp.) suggesting a potential for inter-specific competition. In recent years, the catch of peacock eels has outnumbered the catch of all native sunfishes combined. Peacock eel populations are predicted to continue to increase, highlighting the importance of continued monitoring of their impact on native fish assemblages and food webs.