What Are Those Blue Blobs Washing Up On SoCal Beaches?

By-the-wind sailors have been spotted along the Southern California coastline this spring

Little blue creatures occasionally wash up in large numbers along Southern California’s coast in the spring. But what are they? Where did they come from? Why are they washing up on our beaches? 

Anya Stajner, a biological oceanography PhD student at UC San Diego’s Scripps Institution of Oceanography, said these creatures are a species known as Velella velella or “by-the-wind sailors.” Their common name refers to their sail-like appendage that sticks up above the water. 

Velella Velella
Photo of Velella velella by Linsey Sala.

“Velellas float on the surface of the ocean and are passively moved across the water by the wind that catches their sails,” said Stajner, who studied these organisms as an undergraduate student. “Sometimes, when the wind is blowing towards the shore, large numbers of velellas get washed ashore like we’re seeing now.” 

Although they may resemble jellies, they are not in the same group as true jellies. True jellies are part of a group called scyphozoans and Velella velella are part of a different group called hydrozoans. Velellas are more closely related to animals like the Portuguese man o’war. Velella do have stinging cells within their tentacles, but they are usually harmless to humans.

According to Scripps Pelagic Invertebrate Collection Manager Linsey Sala, Velella velella entered the scientific record in 1758. These creatures, which reach about three or four inches in diameter, are commonly seen off the coast of California and further north off Oregon and Washington.

"They have a pretty complex life history. There are additional stages where they will reside in the deep sea during the wintertime. Then, when conditions are such that they support a lot of zooplankton activity, like we see here in the spring, they transition to the stage with the sail, and they make an excursion from the deep sea up to the surface,” Sala said. "That's when we start to see them in their feeding stage, with their tentacles trailing underneath them just below the surface."

The movement patterns of velellas are unpredictable, but they are most likely to show up on Southern California beaches during late spring and early autumn as a result of local wind patterns and food availability.

To learn more about Velella velella, see below for our experts’ answers to some frequently asked questions.

Velella velella under the microscope
Velella velella under the microscope
Photos of Velella velella under the microscope by Anya Stajner.

Velella velella Q&A

What are these blue jellyfish-like creatures?

These creatures are called Velella velella. They have several different nicknames including “by-the-wind-sailors” and “little sails” as a reference to their sail-like, chitinous structure that sticks up above the water.  

Why are they washing up?

They wash up on shore due to a combination of shoreward wind and current patterns. Velellas float on the surface of the ocean, have no means of locomotion, and are moved across the water by ocean currents and the wind that catches their “sails.”

Where can I find them?

While Velella velella are a species that are typical in warm and temperate waters, it is not easy to predict when and where you can find them. Your best bet at finding them on the beach is during times of increased shore-ward flow. However, keep your eyes out for them if you are boating, surfing, or paddling as you may get lucky to see some on the water, too!

Are they jellies?

The term jellies usually refers to animals within the group Scyphozoa that have a very characteristic umbrella shaped medusa stage, like moon jellies, or our purple striped jelly. However, Velella velella and these true jellies belong in the same higher level group Cnidaria, but Velella vellela are part of a group called Hydrozoa and are more closely related to the Portuguese man o’war. Velella velella are actually a group of individuals or a colony with specific functions put together to make one functional organism.

Are they harmful / do they sting?

Velellas do possess stinging cells and a neurotoxin to stun their small zooplankton prey; however, usually are not strong enough to penetrate or harm human skin. These stinging cells are located in their tentacles, but not the sail. Because we do have other types of stronger stinging jellies that are blue-purple in color that could be challenging for a beachcomber to identify, we usually advise to observe, take photos, but refrain from disturbing them. Velellas are benign to humans. Velellas are a part of a phylum called cnidarian, thus – like jellies – they do have specialized stinging cells at the end of their tentacles called “nematocysts.” However, the stinging cells on velellas are optimized to catch their prey, which are mostly invertebrate zooplankton. 

What do they eat?

Velella velella mostly eat invertebrate zooplankton (small swimming crustaceans like copepods) and the occasional larval fish depending on the size of the Velella and how much food is in the water.

What does the life cycle of these creatures look like?

The life cycle has been suggested to begin in the deep ocean. The 1-2 millimeter sexually reproducing medusa stage releases eggs that are fertilized and develop into a larva. This larva develops a rudimentary float and a structure that secretes oil to make it positively buoyant. These creatures continue to grow, the float enlarges, tentacles and sails appear that allow them to head to the surface and begin to feast on tiny crustaceans they stun into submission with stinging cells and a neurotoxin. This ascent to the surface usually happens in the spring when conditions support a lot of zooplankton food. Then the well-developed sailors release new medusae that descend to the deep to begin the life cycle again.

What happens to them when they wash ashore?

The Velella velella that continue to wash ashore in Southern California will either be pulled back into the ocean by the tide or break down naturally, where they may serve as food for other scavenging critters.

How long can people expect to see them on the beach?

They are most likely to be blown onto beaches during late spring and early autumn due both to local wind, current, and tidal patterns, but this doesn’t happen every year. They are difficult to predict, so keep an eye out for them if you’ve heard reports they are in your coastal area.


To learn more scientific information about Velella velella, see their entry in the Scripps Zooplankton Guide

About Scripps Oceanography

Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.

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