Atum crabs are not really crabs, but a kind of squat lobster. These small, bright red crustaceans normally live in the waters off Baja California in Mexico.
Their name comes from the fact that they prey on tuna, although a number of other ocean creatures, including turtles, seabirds and rays, can enjoy them as a little snack.
These lobsters live their entire lives in the water column, so they are especially vulnerable to changes in currents and tides.
What's more, they're not very strong swimmers and are therefore swept away by currents. This is one of the reasons why experts think so many lobsters appear near San Diego.
"They live in these waters and are swept like birds off their migration route and find their way to California, even further north than we are."
This is not the first time that tuna crabs have been displaced by the tide. In 2015, they also appeared near San Diego, where the colder waters are not good news for the crustaceans, with many turning up dead on the coast.
With several of these strandings occurring, one group decided to investigate the mechanisms behind them, after witnessing one first-hand in 2018. The team discovered that an atypical current flowing from Baja California to central California was the main culprit.
Michael Jacox, a physical oceanographer with dual affiliations at NOAA and UC Santa Cruz, said he thinks "it's very important that when we think about climate change, we don't just think warm temperature equals some response and we really try to dig into the mechanisms."
