Ontogenetic and Temporal Diet Shifts of the Invasive Asian Swamp Eel in South Florida

The Asian Swamp Eel Monopterus albus is an introduced species in South Florida waters and is considered to be a potential threat to the native biota and ecosystems in the region. As a protogynous hermaphrodite that, under the right climatic conditions, can travel short distances over land and tolerate abrupt shifts in salinity, this species has strong invasive potential. In this study, our main goal was to evaluate the potential effects of the Asian Swamp Eel as a predator on native fishes and other biota. Our specific objectives were to (1) analyze the stomach contents of introduced Asian Swamp Eels from canals located near Everglades National Park and (2) assess the ontogenetic and temporal shifts in their consumption of prey. We dissected 752 Asian Swamp Eels (107–833 mm TL), and 46.4% (N = 349) of the samples had stomach contents for the analyses. The analyses indicated that amphipods, fishes, dragonfly nymphs, Hemiptera insects, and grass shrimp Palaemonetes were the most important prey items for Swamp Eels. Swamp Darters Etheostoma fusiforme, juvenile Asian Swamp Eels, and centrarchids were the most common fishes eaten by Swamp Eels. Ontogenetic shifts in diet were apparent, with amphipods and dipteran larvae most often observed in the stomachs of small‐ to medium‐sized Swamp Eels and fish, dragonfly nymphs, and Hemiptera insects more commonly identified in the stomachs of larger eels. The Swamp Eels also became increasingly piscivorous with size. Dragonfly nymphs and grass shrimp occurred more frequently in the Swamp Eel diets in May 2010, while the consumption of fish and amphipods increased in October 2010. Fish were the most important prey item that was consumed during the November–December 2009 period, although other prey items were relatively important during that collection period. As an opportunistic predator that consumes a wide range of prey, the Asian Swamp Eel likely has its greatest effects on native biota and ecosystems as a predator and competitor with native fishes for resources.