Why Portuguese Man-of-Wars Are Popping Up in New Jersey

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A Portuguese man-of-war and its escort of fish float in the Gulf of Mexico off the coast of Louisiana. Christopher Berkey/EPA

Over the past week, several Portuguese man-of-wars have washed up on the New Jersey coastline, and others have been spotted in the waters. One was seen in Harvey Cedars in mid-June, dozens more in Surf City the week after. Most recently, another was found in Stone Harbor. 

The jellyfish-like creatures are actually a siphonophore, which National Geographic describes as “an animal made up of a colony of organisms working together.” There are four polyps in the man-of-war; the gas-filled bladder is the top one. There are also the tentacles, which can be as long as 165 feet; reproductive organisms; and digestive organisms. Altogether, this makes for a potentially lethal creature.

The man-of-war is able to kill fish and other small sea life with its venom. If a human touches it, an extremely painful sting can result. The sting can be deadly, but only in rare cases. Touching even a dead man-of-war, like those found ashore in New Jersey, can pack a painful wallop.

Most man-of-wars live in warm climates and travel in a pack. This handful of siphonophores likely wound up in Jersey’s chilly waters by accident. 

“It probably came up with the Gulf Stream, and then we had a bit of a north swell move in. So [the man-of-wars] might have drifted in,” John Tiedemann, director of marine and environmental biology at Monmouth University in New Jersey, told Live Science.

Peter Hartney, a councilman in Surf City, seconds Tiedemann’s theory. “Our land happens to be in the direction of the wind and waves. And the water is warm, which is keeping them alive. They probably have enough food to sustain themselves,” he told NJ.com.  

In the event Jersey Shore visitors spot a man-of-war, dead or alive, they’re asked to notify a lifeguard right away.