Tuna Crabs Invade San Diego Beaches by the Thousands The cooler waters are a death sentence for the thumb-sized crustaceans.

 -- Thousands of tuna crabs have invaded the beaches of San Diego Bay.

The thumb-sized crustaceans started washing ashore further up the California coast earlier this year, but turned up this week in San Diego in unusually larger numbers, officials said.

They’ve washed ashore periodically over the years because of any number of natural effects, but research scientist Michael Shane of the Hubbs SeaWorld Research Institute in San Diego cited El Nino as the phenomenon that might have pushed the crabs up from their normal habitat far offshore.

The result is certain death and nothing can be done to save the crabs.

“The crabs start to die because the local waters are much cooler,” Shane told ABC News today. “Local animals have begun to eat the crabs and they have been found in the gut contents of sea lions, fish, and birds.”

The remaining carcasses will remain on the shore until they decompose or are swept back into the water.