Ask ALOysius

About Jellyfish!

Alliance for a Living Ocean

2007 Long Beach Boulevard
North Beach Haven, New Jersey 08008

(609) 492-0222


Some weeks during the summer, there are jellyfish in the water and on the sand. I really don't like them! Why do they suddenly appear?


When I and my friends are swimming off the LBI beaches, and we hear some loud shrieks coming from the swimmers, then we know that the jellyfish have arrived on the beaches. Swimmers don't like it when a large jellyfish in the waves bumps into them, or when they step on jelly-like masses on the beach. A number of types of jellyfish can be found in the waters of the Atlantic Ocean. When weather conditions are right, for example warm winters, the jellyfish's food source can be abundant in the summer months. This may explain when jellyfish are more plentiful in some years than others. In late July and early August, the prevailing winds and ocean currents carry the jellyfish onto the LBI beaches.

Here are three of the large jellyfish found along the Atlantic Ocean beaches.

Lion's Mane Jellyfish

This jellyfish is also known as the Red or Sun jellyfish. It has a bell shaped umbrella and long tentacles. Its color varies with age and size: pink and yellow when small to dark reddish brown when large. Shaggy clusters of more than 150 tentacles are attached beneath 16 pouches or lobes on the underside of the saucer. During most summers these jellyfish cause only minor annoyances to swimmers on Long Beach Island. However, depending upon the prevailing winds and ocean currents, a large number of these jellyfish can be washed up on our beaches. When this happens, swimmers can experience skin irritations such as burning and rashes. During exceptionally large influxes, swimming may be prohibited and the waves take on a reddish appearance.

Moon Jellyfish

The Moon Jellyfish is the jellyfish most commonly washed up on Long Beach Island beaches during the summer high tides and winds. By the time it has been tossed in the rough surf, the Moon Jellyfish looks like a clear plastic disk or saucer lying in the sand. When alive in the ocean it has numerous, short fingerlike tentacles around the edge and an outline of a four-leaf clover in the center. Its transparent umbrella can grow up to 10 inches across. By the time the Moon jellyfish is washed up on the beaches, the tentacles are gone and these jellyfish are harmless.

Portuguese Man-of-War

The Portuguese Man-of-War is actually a colony of individual animals. They share a single gas-filled float. The float can be as small as 4 inches or as large as 2 feet. It is very colorfully tinted with shades of blue, purple and green with a reddish crest on top. The Man-of-War's tentacles can be up to 60 feet long and are poisonous to other sea creatures as well as human swimmers. Very rarely are the Portuguese Man-of-Wars washed up on Long Beach Island beaches, but they can be seen off-shore from boats as they are blown north by the Gulf Stream. They do cause problems for swimmers on beaches from Florida to Texas. If you visit one of these beaches, remember not to touch even a dead one without protecting yourself from the stingers.

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