A few days ago, Digital Journal reported on an invasion, of sorts, of sea hares along some coastal California beaches. The purple blobs fascinated beachcombers and naturalists, alike.
The appearance of the tuna crab on California beaches
In a phenomenon characteristic of warmer ocean temperatures, thousands of tuna crabs, actually a species of squat lobster, Pleuroncodes planipes, also known as pelagic red crabs or tuna crabs, have been washing up on California beaches for the past two weeks.
The tuna crabs, so called because they are a favorite lunch for tuna, as well as other marine creatures, is a bright red animal that gets up to about 5.1 inches long. It resembles a lobster but has a shorter abdomen. The tuna crab lives on the Continental shelf west of Mexico, and can usually be found only southwest of San Diego.
But during El nino events, like what we are experiencing this year, the tuna crab’s range will extend further north along California’s coastline. What made this year’s sighting of tuna crabs so unusual was how far north it occurred. This was the first time in 34 years that residents in Huntington beach had seen the creatures washing up on shore.
In a news release, Linsey Sala, collection manager for the Pelagic Invertebrates Collection at Scripps Institution of Oceanography, UC San Diego, said:
“Scientists are investigating the nature and cause of the massive pool of warm water that developed last year in the Pacific, from Mexico to Canada. The pool helped push sea surface temperatures in San Diego to unusually high levels for part of the winter and spring.”
Sala also suggested the tuna crabs not be eaten because they feed on phytoplankton that may contain toxins, writing, “Due to unknown toxins that may be present within the crabs, human consumption is not recommended.” She also mentioned the crabs are an “indicator species,” of warmer waters, and important ecologically as a food for seabirds during El nino events.