Eel effects: fears after release of exotic species into New York lake

New York state and city wildlife officials say it is too soon to know what effect a dump of exotic eels into a lake in a park in Brooklyn last month will have on local species – but it could become a major problem.

“People like animals and they sometimes think they’re doing a good thing by letting them go,” said Jason Munshi-South, an urban ecologist at Fordham University. “Most will die. Some will become a problem, and then there’s no going back.”

One day towards the end of September, Andrew Orkin was sitting by Prospect Park lake when he turned and was startled to see a tangle of wriggling snakes.

“And quite a big pile – fully alive,” said the composer, who lives near the park.

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The “snakes” turned out to be eels that had escaped from one of two large plastic bags as a man dragged them to the shoreline. After dumping the eels in the water the man walked away, explaining to bystanders: “I just want to save lives.”

The illegal release became a curiosity on social media, but the dumping of exotic animals in urban parks is nothing new. Across the US, non-native birds, turtles, fish and lizards have settled into, and often disturbed, local ecosystems. New Yorkers free thousands of non-native animals every year. Many abandoned pets quickly die but others can survive, reproduce and cause lasting harm.

Based on photos taken by bystanders, officials identified the eels in Prospect Park as swamp eels native to south-east Asia, which have been found in at least eight US states. Once introduced, often after being purchased at live fish markets, the eels eat almost anything including plants, insects, crustaceans, frogs, turtles and other fish. In Brooklyn, they could prey upon or compete with the park’s native species for however long they survive, said Katrina Toal, deputy director of the New York City parks department’s wildlife unit.

But there are no plans to eradicate the eels, which are nocturnal and spend most of their time burrowed in the sediment of lakes, rivers and marshes.

“This kind of species is a little tricky. They’re well hidden,” Toal said. “We’ re not going to go out there and try to trap any of them.”

Officials from the New York state environment department could not specify the number of eels released. Bystanders described seeing more than 100. Officials say they will look for swamp eels during the next survey in the spring, but don’t expect them to make it through the winter.

However, University of Toronto freshwater ecologist Nicholas Mandrak said: “Even if they don’t survive, they could have negative short-term impacts.”

If some Prospect Park transplants survive for a few years, climate change could feasibly warm waters enough to render them hospitable, Mandrak said.

“We shouldn’t come to an immediate conclusion that because they’re found in Asia they couldn’t survive in New York City,” he said.

The eel species has shown up in western New York’s Hemlock and Canadice lakes in 2019 and Queens’ Meadow Lake in 2017. Biologists have found Asian swamp eels in Hawaii, Georgia, New Jersey, Maryland, Michigan, Florida and Pennsylvania.

New York City has a long history of people introducing exotic species into its parks. In 1890, Shakespeare enthusiasts released about 60 European starlings in Central Park – the current population of hundreds of millions nationwide outcompetes native birds, destroys crops and occasionally snarls jet engines.

For decades, pet red-eared slider turtles have been abandoned in city ponds, creating a major nuisance that has crowded out local painted turtles and fueled algae blooms. Voracious, sharp-toothed northern snakehead fish, introduced by way of live food markets and aquarium hobbyists, have been spotted in Harlem Meer and Flushing Meadows Corona Park. Descendants of escaped or released monk parakeets and Italian wall lizards are scattered across the city’s boroughs.

The eels in Prospect Park are “an unusual and eye-catching story”, Toal said, “but something that happens far more often is people release one unwanted pet”.