Invasive Australian Spotted Jellyfish Washes Up on Texas Beach

The prolific jellies can form huge swarms and clear zooplankton from wide areas of water, sending ripple effects up the food chain

large spotted jellyfish with thick tentacles swimming in dark blue water
Australian spotted jellyfish typically reach up to 18 to 20 inches in diameter. Orest via Wikimedia Commons under CC BY-SA 2.0

An invasive jellyfish native to the western Pacific Ocean has washed up a long way from home—on a Texas beach. Wildlife officials at Padre Island National Seashore discovered an Australian spotted jellyfish (Phyllorhiza punctata) on the sand late last month, they revealed Friday in a Facebook post.

They shared a photo of a gelatinous, semi-translucent blob with white polka dots splayed out on the sand of North Beach, a stretch of shoreline along the Gulf of Mexico. While the creature is certainly eye-catching, officials pointed out that it’s a “not-so-welcome visitor” to the national seashore.

That’s because Australian spotted jellyfish—also known as white-spotted or brown jellyfish—can decimate zooplankton populations, setting off ripple effects up the food chain. Traveling in huge swarms, each of these creatures can eat all the plankton within 65 cubic yards of water in a single day, according to the Texas Invasive Species Institute.

Fortunately for beachgoers, Australian spotted jellyfish are largely harmless to humans. Their mild venom is “so weak they can’t use it to stun prey,” per the Padre Island National Seashore.

First described in 1884, Australian spotted jellyfish live off the coasts of Australia, Japan, Thailand and the Philippines in the Pacific and Indian oceans. They made their way to the Hawaiian Islands by at least 1945 and populated the Gulf of Mexico by 2000.

This is not the first time the invaders have been sighted off the coast of Texas, according to the U.S. Geological Survey (USGS). A few have also been spotted farther north, near Galveston.

Scientists don’t know for sure how the jellies have been able to cover such vast distances, but they suspect some of them may have hitched a ride on ships during their early-life polyp stage. One of the ways jellyfish reproduce is by releasing large amounts of sperm and eggs into the water. When a sperm and an egg meet, they produce a larva, which typically sinks to the bottom of the ocean and attaches to a hard surface, where it becomes a polyp.

These polyps can persist for decades until the ecosystem has enough food and the right water temperature for their survival. A single polyp can release large numbers of jellyfish, and scientists believe fields of polyps cover the ocean floor, turning some parts of the seabed into “veritable jellyfish factories,” per the National Science Foundation (NSF).

From the polyp stage, adult jellyfish go into what’s known as the “medusa” phase, when they take on the iconic bell shape with tentacles dangling underneath. In this stage, Australian spotted jellyfish normally grow up to 18 to 20 inches in diameter. But they seem to be thriving in the Gulf of Mexico, where it’s not uncommon for them to reach 24 inches. In one instance off the coast of North Carolina, scientists measured one with a 28-inch diameter bell.

And the jellies seem to be spreading: They’re present along the Atlantic coasts of North Carolina, South Carolina and Florida. They’ve also been spotted off Southern California.

Map of the US
A map of reported Australian spotted jellyfish sightings in the U.S. as of July 1, 2023 U.S. Geological Survey

But as of now, not much can be done to stop them, as the Texas Invasive Species Institute notes. Fishermen could capture the jellyfish, but there are so many that it would be an impossible task—plus, with no market for these animals, fishers would basically be donating their time and energy to the cause. Some snails eat jellyfish polyps, but these are only present in the Pacific region—not in the Gulf of Mexico or Atlantic.

“There isn’t much known on how to manage these jellyfish populations, especially since they are found in wide open ocean areas,” the institute writes.

If beachgoers see one on the sand, they should keep walking. When the jellyfish wash up on the beach, they die and dry out quickly.

“They will get eaten by seagulls, crabs and other scavengers, and whatever is left of it will eventually decompose into the sand,” per a comment from the national seashore on the Facebook post.

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