Massive numbers of bright red tuna crabs have washed up on San Diego beaches over the past several weeks. Pleuroncodes planipes (also known as tuna crab or pelagic red crab), have been seen in droves along the San Diego coastline, from Ocean Beach to La Jolla.

“Typically such strandings of these species in large numbers are due to warm water intrusions,” said Linsey Sala, collection manager for the Pelagic Invertebrates Collection at Scripps Institution of Oceanography, UC San Diego. Because of the long sampling history of the CalCOFI (California Cooperative Oceanic Fisheries Investigations) program, unusual events such as these can be compared and evaluated in context with other events in the program’s 66-year history.”

Tuna crabs primarily inhabit the west coast of Baja California, Gulf of California, and the California Current. The species is unique in that it can live its entire life cycle in the water column (surface to seafloor), from larvae to adulthood. Larger adult tuna crabs are known to inhabit the epibenthos (just above the seafloor), and make vertical excursions to the surface to feed on phytoplankton. Because they live in the water column, they are subject to the winds, tides, and currents.

Due to unknown toxins that may be present within the crabs, human consumption is not recommended.

• For more natural history information on tuna crabs, see the Zooplankton of San Diego Region website entry for this species: https://scripps.ucsd.edu/zooplanktonguide/species/pleuroncodes-planipes

• Video

• Photo gallery

Related Image Gallery: Red crabs Invade San Diego

Related Video: Tuna crab invasion