Red crab tide hits Orange County

Thousands of tiny tuna crabs have washed ashore in Dana Point, California. Photo / AP

They washed in by the thousands: tiny red crabs covering the Orange County shoreline much further north than their typical home.

The one- to three-inch Pleuroncodes planipes are usually concentrated off the Baja California coast, said Linsey Sala, collection manager at University of California San Diego's Scripps Institution of Oceanography.

The crabs are washing up further and further north because the water is unusually warm, she said.

"They have this ability to transition from the sea floor through the water column.

"They're subject to current and internal waves and tides, so they can be pushed along with different water masses," Sala said.

"Typically, when we do see larger numbers of tuna crab, it's during warm water intrusions."

Fishermen first spotted the little red crabs in Southern Californian waters last year, Sala said, and reports came in earlier this year of sporadic strandings on Catalina Island and elsewhere.

Starting in mid-May, thousands washed up on San Diego beaches.

The warmer water could be due to a combination of factors, Sala said, including an El Nino, a large-scale oceanic climate phenomena.

A giant patch of warm water, nicknamed "The Blob" by researchers, has formed in the Gulf of Alaska and off California's coast as weather patterns have failed to suck the usual amount of heat from the ocean.

- Washington Post-Bloomberg