Diet of the Nonindigenous Asian Swamp Eel in Tropical Ornamental Aquaculture Ponds in West‐Central Florida

The nonindigenous Asian swamp eel Monopterus albus is established in west‐central Florida, where it invades tropical ornamental fish production ponds. The economically valuable ornamental fish industry (US$42 million in 2003) is dominated by the production of small‐bodied fishes cultured at high densities in small, earthen ponds. Although introduced Asian swamp eels have been described as voracious predators of fish, to date there have been no published studies containing quantitative diet information on any of the introduced populations found in the USA. The purpose of our study was to evaluate the possible effect of nonnative Asian swamp eels on the aquaculture industry by analyzing the diets of Asian swamp eels that have invaded small ponds used for the culture of ornamental fishes. We examined 71 Asian swamp eels ranging from 94 to 864 mm in total length (TL) that were taken from ornamental aquaculture farms. Fifty‐two percent lacked stomach contents; otherwise, prey were relatively small and generally few in number, resulting in low values of stomach fullness. Prey items included amphipods, crayfish, fish, fish eggs, insects, oligochaetes, organic material, plant material, and a tadpole. Insects were the most frequently occurring prey and fish were second. Fish eggs dominated by number but were found in only two individuals. Fish was the heaviest prey category, closely followed by insects, fish eggs, and crayfish. Only 10 fish prey were found in 8 Asian swamp eels (including a cannibalized individual), primarily in the largest predators (≥570 mm TL). Our diet results were surprising, given the highly vulnerable prey fish found in the sampled ponds. We conclude that this species represents a low threat to the Florida ornamental aquaculture industry. We recommend that producers continue to use best management practices, but aggressive control or eradication of Asian swamp eels is not warranted.