Warning! Clinging Jellyfish
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Warning! Clinging Jellyfish



State officials have issued a warning to New Jersey residents this holiday weekend about clinging jellyfish.

Those are back in the Shrewsbury River in Monmouth County. For such small and delicate creatures, they can pack mighty painful stings. Known as clinging jellyfish due to they attach themselves to sea grasses and seaweeds, Gonionemus is found along coastlines in the Pacific and Atlantic oceans, and in particular in waters near Vladivostok, Russia.  Exactly how these jellyfish, long assumed to be native to the North Pacific, became so widely distributed throughout the world was a puzzle for researchers for decades.


• Clinging jellyfish are small, the bell about dime to quarter-sized

• They come out at night in shallow, low velocity waters (coastal embayments)

• Daytime: hang onto vegetation and substrates like shells. The tentacles have adhesive pads that allow the jellyfish to ‘cling’ to various media

• CJ’s do not have long tentacles, but have 60-90 that can extend out laterally to about 3 inches

• The tentacles contain nematocysts (or stinging cells) that can cause significant pain if touched

First observation of CJ was  in New Jersey in 2016 (Manasquan River at Point Pleasant Canal). Likely source from marine vessel that spent time in MA and contained attached polyps on surface, or potentially in ballast.

This week researchers found about 40 of them in an area off Monmouth Beach known as The Hook.

The CJ Sting:

  • NOT Deadly, but CJ can pack a powerful sting, CJ’s do not actively attack, firing of the nematocyst is purely mechanical (designed to fire when contacted)
  •  CJ’s have been observed to “swarm” when physically disturbed from their substrate, but this is thought to be a flight response Sting Symptoms:
  • Visible: swelling or a reddened whelt at point of contact, similar to “Irukandji Syndrome”
  • Systemic: intense pain at and around sting, other physiological and psychotic effects (eg. Feeling of “impending doom”)

After 30 minutes:

1. Severe lower back pain

2. Excruciating muscle cramps

 3. Reduced control of extremities

4. Sweating

5. Anxiety

 6. Restlessness

7. Nausea/Vomiting

8. Headache

9. Irregular heart beat

10. Hypertension

11. Pulmonary edema

12. Heart dilation Pain and other symptoms can last for 3 -5 days, hospitalization may be required.


  • Apply white vinegar to the affected area to immobilize any remaining stinging cells.
  • Rinse the area with salt water and remove any remaining tentacle materials using gloves or a thick towel.
  • A hot compress or cold pack can then be applied to alleviate pain.
  • If symptoms persist or pain increases instead of subsiding, seek prompt medical attention.
Author: USA Really