Forecasting Sea Nettles

The jellyfish often encountered in the Chesapeake Bay in the summer is the sea nettle Chrysaora quinquecirrha. Knowing where and when to expect this biotic nuisance may help to alleviate an unpleasant encounter.


Sea nettle probabilities—updated hourly—are also available at each of the NOAA Chesapeake Bay Intepretive Buoy System observing locations.

Chrysaora quinquecirrha is white and occurs most abundantly in the tributaries of the middle Bay, where salinities range from 10 to 20 parts per thousand (ppt). In the southern Bay, it often has red/maroon markings on the long central tentacles and on the swimming bell. C. quinquecirrha occurs from Cape Cod south along the U.S. East Coast, Caribbean, and Gulf of Mexico; it abounds in the Chesapeake Bay in numbers unequaled elsewhere.

The maps above, generated by the National Centers for Environmental Prediction and the National Ocean Service, depict the probability of encountering sea nettles in the Chesapeake Bay and its tributaries. They are numerical model quidance only; they are not fully validated and may not reflect actual conditions.

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