Dead Humboldt squid washed up last week in Crystal Cove and other Orange County beaches.
The site surprised beachgoers and surfers, but officials said it was a natural occurrence and not a cause for alarm.
One startled bird-watcher emailed pictures of the squid at Crystal Cove to the Coastline Pilot.
"Right away we could tell something interesting was happening because there were hundreds of gulls along the shore," John Heussenstamm wrote in an email. "Along with this there was a repulsive rancid odor filling the air and as it turned out there were hundreds of large dead squid piled up and lining the tideline. Gulls were gorging themselves on the remains and all in all it was a filthy holy mess."
A few examples of the species were spotted on the sand in Newport Beach as well, but more were being caught off-shore.
David Schmitt, a manager at Davey's Locker Sportfishing & Whale Watching in Newport, said fishing excursions have been catching thousands of Humboldt squid over the last few days.
He said the coast periodically sees an invasion by the squid.
"They show up, and they eat everything in sight, not including people," he said.
The Orange County Register reported that 100 to 200 Humboldt squid washed up in San Clemente.
Ian Burton, a marine safety officer, said the squid, about 18 inches long, were covering the San Clemente beach when he went to work Thursday morning. City maintenance crews spent a couple of hours cleaning them up, he said.
Andrew Hughan, a spokesman with the California Department of Fish and Game, said the squid die-off was a natural occurrence. The squids spawn, then die.
"They do what they do, and then they call it in," he said.
—Los Angeles Times and staff reports