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By-The-Wind Sailors Turn Manhattan Beach Blue

May 06, 2024 09:14PM ● By Zachary Fratello

Closeup of the Velella velella, or By-The-Wind Sailor (stock photo).

It’s not uncommon to see things washing up along the shore in Manhattan Beach - kelp, seagrass, shells, unfortunate pieces of garbage, and the occasional oddity. However, within the past few weeks, peculiar blue organisms have been carpeting the beach landscape.

These odd little creatures are known as the By-The-Wind Sailors, or Velella velella. They are small, oval-shaped organisms with thin, plastic-y skin, an iridescent blue base with tiny blue tentacles, and short, transparent sail-like appendages. They are a species of sea jelly, or more specifically a hydrozoan - like their (scarier) relative, the Portuguese Man-o-War. 


While other well-known “true jellies”, like the Moon Jelly, are "neutrally buoyant" (meaning they neither float or sink), hydrozoans float on the surface of the water. They have no way of propelling themselves through the water, instead relying solely upon the wind and ocean currents to carry them while they sweep their hanging tentacles into microscopic prey for them to eat. (While the Sailors' stings may be dangerous to the planktonic organisms they feed on, they are not harmful to humans.)

By-The-Wind Sailors are found in most temperate and tropical oceans around the world, and are usually found very far from shore where they have no risk of washing up on a beach. Despite being so abundant, it takes a very specific set of conditions for these jellies to come ashore in such large quantities.

So what has led to these strange visitors beaching themselves up and down the coast?


(Photo credit: Zachary Fratello)

It is believed that warmer-than-average winters result in significant population increases, meaning that Sailors exist in greater numbers during El Nino years like 2024. During early spring, strong winds blow from the northwest, leading this army of small jellies slowly and perilously closer to shore. They have been washing up in large numbers along the north coast since February, and the California current has been slowly pushing them down the coast, blanketing the beaches in their wake. Within the last few weeks, they have finally reached the end of their journey in Southern California. It is likely they will continue to wash ashore into June. Ultimately, the warming summer waters will lead to a die-off of many of the remaining Sailors, while the weakening of the winds means that the rest of the Sailors will simply stay restricted to their offshore habitat.

While this mass beaching may be an inconvenience to beachgoers, at least some local wildlife benefits from the large influx of Sailors. The Ocean Sunfish, Mola mola, is an odd fish with a strange disk-shaped body and thick leathery skin. They are better known for their clumsiness and immense size, making it difficult for them to chase down and catch anything with a brain. Luckily for them, By-The-Wind Sailors not only lack a brain, but any way to move their body. As such, they are an easy snack for a hungry Sunfish. The Sunfish have been frequently spotted eating thousands of Sailors per day, rising up and scooping two or three at a time off the sea surface.

(The "clumsy" sunfish, who will happily eat By-The-Wind Sailors. Photo credit: Zachary Fratello)

If you see By-The-Wind Sailors on the beach, it's fun to look at them and wonder what kind of journey they had before reaching Manhattan Beach. But even though they won't sting you, you should generally avoid touching them. They'll eventually disintegrate and get washed, circle-of-life style, back into the ocean.

Zachary Fratello is a junior at Da Vinci Science High School. He is conducting research on local fish populations as part of the Southern California Academy of Sciences' Research Training Program.

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