As first reported by Ocean Beach Bulletin, San Francisco residents this morning spotted tens of thousands of jellyfish that had washed up on the shores of Ocean Beach for no apparent reason.

“There was a large swell overnight that may have been responsible,” National Park Service spokesman George Durgerian said.

Durgerian was incredulous at the sight of the jellyfish. He said he’s only seen an incident like this once before.

“It was huge, like a cobblestone walkway made of jellyfish,” he said.

Jellyfish packed a section of beach stretching about three miles long and 20 feet wide. It was easily seen between Pacheco and Lawton streets.

Durgerian said the jellyfish that washed up are a fairly common breed called moon jellyfish.

“These were jellyfish like you think they look like–large, circular, translucent and gelatinous,” he said.

The incident he saw about seven years ago on Ocean Beach involved by-the-wind sailor jellyfish, also known as Valella jellyfish. “They kind of look like a windsurfer,” Durgerian said. Valella are typically deep blue in color.

Durgerian doesn’t know why the jellyfish washed ashore between Friday and today, but said a park service biologist will begin an investigation into the unusual event on Monday.

He said there was no planned cleanup or rescue for the jellyfish. “By now the high tide has come in and they may be off the beach,” he said at about 7 p.m.

Saul Sugarman, Bay City News

All Photos: Mark Lukach, Ocean Beach Bulletin

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