Point Reyes Light - April 11, 2002

By-the-wind-sailors cover Stinson's four beaches

By Gregory Foley

Visitors who crowded into Stinson Beach last weekend hoping to sunbathe and play on the federal, state, county, and privately owned beaches were greeted by an unusual site: piles of stinking, blue-purple corpses.

The remains of tens of thousands of small jellyfish called by-the-wind-sailors, (or velella velella) stretched from the lifeguard tower north to Bolinas Channel. Tentacles and plastic-like discs from the velellas, which are sometimes mistaken for stinging Portuguese man-o-wars, started washing ashore last Thursday and Friday.

By the weekend they littered the sand in rows that moved with the tides. Although the waves of additional by-the-wind-sailors dropped on Sunday and Monday, they rose again on Tuesday, mostly at the north of Seadrift Beach.

Beach nearly covered

Scott Tye, owner of Off the Beach kayak and surfboard rentals in Stinson Beach, noted the northern section of beach was nearly covered on Tuesday. "They’re still coming in," he added Wednesday. "It was pretty thick yesterday. It looked like a blue beach."

Ed Ueber, manager of Gulf of the Farallones National Marine Sanctuary, noted the by-the-wind sailors are relatives of the Portuguese man-o-war.

What the public saw last weekend, he said, are the by-the-wind-sailors’ hard discs, which are made of a bone-like substance called chitin. These are the jellyfish’s sails that allows them to move with the winds.

Velella velellas are typically three to four inches long and 1.25 inches thick, with tentacles that dangle up to five inches below the body, Ueber said. The edges of the discs are ringed with tiny stinging tentacles, but the stings have little or no effect on humans.

Spring blooms

Velella populations explode each spring when strong winds from the northwest and ocean currents from the south combine to cause an upwelling of cold, nutrient-rich water from offshore depths. As tiny plant and animal plankton are swept up to the surface, the velellas feast on the bounty as they are propelled by the winds.

Ueber explained that on occasion the northwest winds blow the sailors close to shore where waves and currents can carry them into beaches. He said that the Farallones Sanctuary along the West Marin coast has two eddies that can carry many surface creatures onto the shore. While the eddies do not have a fixed location, Stinson Beach is often the center of one location where matter is circulated onshore, he said.

"Often they don’t come ashore like they have [this past week], but when there’s upwelling and the wind is in the right direction, it is common," Ueber said. He noted that large numbers also came ashore at Stinson Beach in 1982, 1989, and 1993.

Mistaken for oil slick

Ueber said he has received reports of hundreds of thousands of velellas "blooming" up and down the coast and up to 50 miles out to sea. Last week, Ueber received two calls from the Coast Guard reporting an oil slick off the West Marin coast, so the Marine Sanctuary manager had to tell them "what it was."

Ueber noted the velellas’ recent appearance seemed to have been concentrated around Stinson Beach and that he had not received reports they had come ashore elsewhere in the sanctuary. However, the velellas were reported by other sources to have washed ashore in large numbers as far south as the Monterey Peninsula.

Typically, by-the-wind-sailor blooms can occur anytime during spring upwellings, but by late May or early June, the blooming subsides and most of the creatures die off, he said. "I’d say 99.5 percent of them die within a couple of days," Ueber added. "You wouldn’t want to be one."

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