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Asian swamp eel little threat to US states $60 million aquaculture industry

FLORIDA The Asian swamp eel has been described as a voracious predator of fish that could threaten Floridas $60 million aquarium fish industry, but the exotic eel is not a major problem after all, according to a new University of Florida study.

Asian swamp eel little threat to US states $60 million aquaculture industry FLORIDA The Asian swamp eel has been described as a voracious predator of fish that could threaten Floridas $60 million aquarium fish industry, but the exotic eel is not a major problem after all, according to a new University of Florida study.

When we started this research about two years ago, we were concerned that these eels might affect the states ornamental fish industry, especially if they invaded outdoor ponds and began feeding on fish produced for the aquarium trade, said Jeff Hill, an assistant professor with UFs Institute of Food and Agricultural Sciences. These small ponds are densely stocked with valuable fish, so we need to protect them.

An extensive analysis of the eels diet at UFs Tropical Aquaculture Laboratory in Ruskin shows that they ate a few ornamental fish being raised in ponds, but they preferred to consume a mix of insects, small crustaceans, tadpoles and worms, Hill said.

Jeff Hill, an assistant professor with the University of Floridas Institute of Food & Agricultural Sciences, holds an Asian swamp eel.
Results of the study, which was funded by the U.S. Department of Agricultures Cooperative State Research, Education and Extension Service, will be published later this year in the North American Journal of Aquaculture.

For the study on the feeding habits of the swamp eels, Hill and Craig Watson, director of the Ruskin laboratory, collected eels from seven tropical fish farms in Hillsborough County and one in Polk County. Then the stomachs and intestinal tracts of all the eels were examined to find out what they were eating.

We can now say that the non-indigenous Asian swamp eel (Monopterus albus) compared to other predators represents a low threat to the Florida ornamental aquaculture industry, and it represents less of a predation risk than we anticipated, Hill said. We recommend that producers continue to employ best management practices, but aggressive control and eradication of the Asian swamp eel is not warranted.

Jeff Carter, who operates Carters Fish Hatchery in Wimauma, Fla., said the UF research has helped answer a worrisome question.

When we found a swamp eel at our tropical fish farm about three years ago, we had no idea what was going to happen if they were they were going to eat our fish, mass reproduce and take over our farm, Carter said. Now we know that they do not eat enough fish to hurt our crop or mass reproduce. We have been able to continue business without concern about our future being jeopardized by this aquatic animal.

Hill, who is often asked what to do if someone comes across a swamp eel, said they are not dangerous to people, and the best course of action is probably simply to leave the eels alone. He said it is illegal to release swamp eels, or any other non-native fish, from one body of water to another.

Because they are not protected by law, you could collect them if you wanted to, Hill said. They are a food fish and considered a delicacy in various Asian cultures I have eaten Asian swamp eels, and they are OK.

He said Asian swamp eels are not true eels, but relatively advanced fishes with eel-like characteristics. Unlike swamp eels, the American eel, which is a true eel, has fins. Florida also has two groups of native amphibians that may be confused with swamp eels amphiumas and sirens. The amphiumas have four tiny legs and the sirens have two small front legs and prominent, bushy gills. Asian swamp eels do not have legs or external gills.

Common throughout Asia from India to China, the eels are now in Florida, Hawaii and Georgia, where there is a small population north of Atlanta. Hill said researchers are not sure how the eels entered Florida, but the fish is now established in at least three areas of the state waterways in Homestead, Miami and the Tampa Bay area.

Swamp eels breathe air, can live in shallow bodies of fresh water such as canals and ditches and often follow floodwaters after heavy rains, he said. During drought periods, the animals burrow into mud. Given their ability to survive cold winters in northern Georgia, its likely that the Florida population will spread even further.

Hill said scientists are particularly concerned about their probable invasion of Everglades National Park, where some believe they would have a negative impact on native fish in the protected ecosystem. The biggest problem swamp eels pose for park managers is the National Park Services legal mandate to remove exotic species from parks, he said. Given the unique biology of swamp eels, they can be difficult to eradicate or control once they are established.

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