What jellyfish live in Chesapeake Bay and Virginia waters
Most of the jellyfish you will see in the Chesapeake Bay and along Virginia's coast fall into a handful of types. Only some of them sting in a way that bothers people. This guide covers the common ones, what they look like, when they show up, and whether they sting.
The one that matters most for summer swimmers is the sea nettle. Our daily forecast is built around sea nettles, because they are the main stinging jellyfish in the bay. If you want today's outlook, check the Virginia jellyfish report for your area.
Sea nettle, bay nettle, jellyfish: what to call them
The same animal goes by several names around the Chesapeake, which makes searching for information confusing. Here is what each one means.
- Jellyfish is the everyday word, and the one we use most on this site. A sea nettle is a jellyfish.
- Sea nettle is the common name for the stinging jellyfish that summer swimmers actually run into here. VIMS and NOAA both title their forecast products "sea nettle," which is why you will see the term on our data pages.
- Bay nettle is the more precise name for the Chesapeake's own species, Chrysaora chesapeakei. Researchers separated it from the Atlantic sea nettle (Chrysaora quinquecirrha) in 2017. In casual use around the bay, "sea nettle" and "bay nettle" mean the same animal.
- Stinging jellyfish is a useful way to say what you actually want to know, since several harmless look-alikes drift in the same water.
- Sea jelly or just jelly shows up in science writing, because a jellyfish is not a fish. Same animal.
One name that is not this animal: stinging nettle is a land plant (Urtica dioica) that stings your legs on a hiking trail. It is unrelated to jellyfish, and the first aid is different. If you brushed a weed on a path, this is not the guide you want.
Bay nettle (sea nettle)
Scientific name: Chrysaora chesapeakei. This is the jellyfish people mean when they say "the jellyfish are bad." It has a whitish, saucer-shaped bell with long, trailing tentacles and frilly arms underneath. Some have faint reddish-brown stripes on the bell.
When: Summer, mostly. Sea nettles like warm, moderately salty water, so they build through mid and late summer and fade in fall. See the jellyfish season guide for the full timing.
Sting: Yes. The sting is usually painful but not dangerous for most healthy people, causing a burning welt. If you get stung, see our jellyfish sting first aid guide.
Moon jelly
Scientific name: Aurelia aurita. Moon jellies are the clear, saucer-shaped jellyfish with four pale rings near the center of the bell that look like a four-leaf clover. Their tentacles are short and fine, more like a fringe than long trailing lines.
When: Warmer months, often alongside sea nettles.
Sting: Very mild. Moon jellies have a weak sting that most people barely feel, if at all. They are generally considered harmless to swimmers, though sensitive skin can react to any jellyfish.
Lion's mane jelly
Scientific name: Cyanea capillata. In the Chesapeake this is sometimes called the winter jellyfish. It has a reddish or brownish bell and a thick, hair-like mass of tentacles underneath, which is where the "lion's mane" name comes from.
When: Cold months. Unlike sea nettles, lion's mane shows up in late fall, winter, and early spring, when the water is cold. This is why our summer sea nettle forecast does not track it.
Sting: Yes, it can sting. Since it appears in cold weather, few people are swimming when it is around, but watermen and cold-water paddlers may run into it.
Comb jellies
Comb jellies are not true jellyfish. They are a separate group of animals called ctenophores. In the bay they look like small, clear, egg-shaped or walnut-shaped blobs that drift in the water and can shimmer with rows of tiny moving combs.
When: Common much of the year, and they can be very abundant.
Sting: No. Comb jellies do not sting people. If you scoop up a clear jelly that has no long tentacles and does not hurt to touch, it is very likely a comb jelly, not a sea nettle.
Portuguese man o' war
Scientific name: Physalia physalis. Like the comb jelly, this is not a true jellyfish, but it is worth knowing about. It has a gas-filled float that sits at the surface, often bluish or purple, with long stinging threads hanging below.
When: Rare in Virginia, and an ocean animal, not a bay one. It occasionally drifts up onto the Atlantic oceanfront, usually pushed in by wind and currents. It is not a normal part of the Chesapeake Bay picture.
Sting: Yes, and it can be quite painful. The sting is stronger than a sea nettle's. Never touch one on the beach, even if it looks dead, because the threads can still sting. First aid for a man o' war sting differs a little from sea nettle care, so read the notes in our sting first aid guide.
How to tell them apart quickly
A quick field guide:
- Long trailing tentacles and a burning sting: most likely a sea nettle.
- Clear saucer with a four-ring clover shape and little or no sting: moon jelly.
- Reddish, hairy mass of tentacles in cold weather: lion's mane.
- Small clear blob, no long tentacles, no sting: comb jelly, and not a true jellyfish.
- Blue or purple float on the ocean beach: Portuguese man o' war. Do not touch.
For where and when these turn up around the state, check your local Virginia beach page, and see the about the data page for how our forecast is built. You can also read more about the sea nettle model at VIMS.