Every few years, a red carpet rolls out in Southern California. But instead of gracing a Hollywood premier, this less-than-walkable rug unfurls on the beach—and it’s made of tiny crustaceans.
Called pelagic red crabs, the animals look like small lobsters or crawfish and measure one to three inches long. And they’re not even true crabs—rather, these crustaceans are a species of squat lobster that normally live off Baja California.
Pelagic red crabs are not strong swimmers, so they migrate by drifting with the tide, winds, and currents. During warming events when southern waters move poleward, especially those related to El Niño, countless crustaceans ride currents up to southern and central California.
But upon getting to these northerly locales, the shock of the cold water hits them.
“The [pelagic red] crabs start to die because the local waters are much cooler,” Michael Shane, director of fisheries enhancement at the Hubbs-SeaWorld Research Institute, told ABC News in 2015 when a stranding happened.
During one of these strandings, Steve Webster, a senior marine biologist at the Monterey Bay Aquarium, observed seagulls gorging on so many of the crustaceans they couldn’t fly. When they washed ashore on Santa Catalina Island during another stranding, roughly 100 kids tried to save them by collecting them in buckets and dumping them back into the ocean.
The crustaceans rarely get much further than California, but in spring of 2017, they were spotted on the beaches of Oregon, possibly for the first time.
Pelagic red crabs are called “tuna crabs” for the fish species that feed on them. They’re also prey for other migratory fish, giant squids, turtles, rays, and whales. Pinnipeds (like seals, walruses, and sea lions) and seabirds are also common predators.
The omnivorous crustaceans graze on phytoplankton in open water, and some larger adults crawl along the sea floor. Pelagic red crabs are not safe for humans to eat because they may ingest toxin-producing plankton.