Trophic niche of a nonnative invader and environmental drivers of its increasing populations in the coastal Everglades

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 15 years of electrofishing data and stable isotope analysis. We investigated the population trends of peacock eels at the marsh-mangrove ecotone of the Shark River Estuary, 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 to determine peacock eel trophic niche size and overlap with native species. Results of this study found that peacock eel abundance has rapidly increased, and their populations are strongly related to hydroclimatic regimes. Peacock eel abundance was positively associated with warmer water temperatures and greater marsh inundation periods. The trophic niche of peacock eels was significantly smaller in volume than that of native sunfishes (Lepomis spp.) indicating lower intraspecific resource use variability and suggesting a limited potential for inter-specific competition with these taxa. However, in recent years, the catch of peacock eels has outnumbered the catch of all native sunfishes combined. The feeding habits and pervasiveness of peacock eels in the coastal Everglades could lead to a decrease in abundance of benthic prey items targeted by peacock eels and alter food web dynamics in the system. Based on these data, peacock eel populations are predicted to continue to increase, highlighting the importance of continued monitoring of their potential impact on native fish assemblages and food webs.