Large congregations of animals can be positive or negative. Large groups of whales seen for the first time may represent an important conservation milestone, while the upcoming cicadapocaplypse might not be everyone’s idea of a good time. Underneath the waves off the coast of California, however, a gathering of tuna crabs is causing a stir.
Tuna crabs (Pleuroncodes planipes) are not actually crabs but rather a species of squat lobster. These tiny bright red crustaceans typically live in the waters off Baja California in Mexico. They get their name from the fact that they are prey for tuna, though a whole host of other ocean creatures including turtles, sea birds, and rays might fancy them for a small snack.
These lobsters live their entire lives in the water column and so are especially vulnerable to changes in currents and tides. They are also not particularly strong swimmers and so get carried with the currents. This is part of the reason why experts think so many of them have appeared near San Diego, and wonder if the effects of El Niño are to blame.
“It’s not that the crabs are deliberately making their way to us,” Dr. Charlotte Seid, manager of the Benthic Invertebrate Collection at the Scripps Institution of Oceanography at UC San Diego told NBC San Diego. “They live in those waters and get swept up sort of like birds outside of their migration route, and they find their way to California, even further north than us.”
Unfortunately, this is not the first time tuna crabs have been relocated by the tide. In 2015, they also appeared near San Diego, where the cooler waters do not spell good news for the crustaceans, with many washing up dead on the shoreline.
With a number of these strandings having occurred, one group was inspired to dig into the mechanisms behind them after witnessing one firsthand in 2018. The team found that an atypical current flowing from Baja California to central California was largely responsible.
“I think it’s really, really important that when we think about climate change, we don’t just think about ‘warm temperature equals some response’, and we really try to dig into the mechanisms,” said Michael Jacox, a physical oceanographer with dual affiliation with NOAA and UC Santa Cruz in a statement made at the time.
Source Link: The Tuna Crabs Are Coming And It's Not Good News
