When Tropical Storm Hilary hit Southern California in August 2023, the first of its kind to make direct landfall this century, most people were focused on the flooding. They weren’t paying attention to what the sharks were doing.
When Tropical Storm Hilary made landfall in August 2023, researchers at UC San Diego’s Scripps Institution of Oceanography and the Shark Lab at CSU, Long Beach were already tracking 22 juvenile great white sharks off the San Diego coast with acoustic tags. The resulting study is the first to document storm-response behavior in white sharks, and the behavior was much more coordinated than anyone expected.
As the storm closed in, more than half the sharks bailed on their nursery off Torrey Pines and Del Mar, retreating to the calmer waters of La Jolla Cove, which sits next to a submarine canyon with quick access to depth. One individual dove 433 feet, probably trying to escape the chop near the surface. Most came back within days.
“We think that some were seeking shelter from the storm,” said co-author Chris Lowe of the CSULB Shark Lab. “It makes sense that not all sharks did the same things, in much the same way people respond differently. It’s a key survival characteristic that humans seem to share, too.”
Great White Sharks May Know When It’s Time to Flee a Storm, and That Could Help Humans
The likely trigger was temperature. Sea-surface temps at the nursery dropped from 68°F to 57°F in under 24 hours as the storm hit. Juvenile great whites are more sensitive to cold than adults, and researchers believe that drop was the cue. “To our knowledge, this is the first study to document storm-response behavior in white sharks,” said lead author and Scripps PhD student Jack Elstner.
Meanwhile, on the East Coast, researchers at the University of Delaware are running a different experiment with a similar cast of characters. They’re attaching electronic tags to shortfin makos, blue sharks, smooth hammerheads, and juvenile great whites to pull ocean temperature and salinity data from the Atlantic. The data feeds into hurricane intensity forecasting, specifically around the Mid-Atlantic’s “cold pool,” a layer of bottom water under 50°F that affects how fast storms strengthen before hitting shore.
“For hurricanes, warm water is the gas, and cold water is the brakes,” doctoral candidate Caroline Wiernicki told the University of Delaware. “Depending on where that cold pool is relative to the shore, that will impact how strong a hurricane is when it makes landfall.”
Sharks are clearing out ahead of storms and simultaneously serving as floating weather stations for the scientists trying to forecast them. That’s a pretty good week for shark research.
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