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While the odds of dying in a shark attack are extremely low—around 1 in 3.7 million—there’s still a small risk. Recent reports show that white sharks are becoming more common along California’s coastline due to federal protections. Meanwhile, Cape Cod experienced its first fatal shark attack in over 80 years.
A new study, published in Frontiers in Marine Science, may help us better understand what’s lurking in the waters. The team, including researchers from UC Santa Barbara and the U.S. Geological Survey, hypothesized that environmental DNA (eDNA)—genetic material shed by organisms—could reveal the presence of white sharks in specific regions off California’s coast.
White sharks leave behind a unique trail in the water, shedding skin, mucus, feces, and other genetic markers. The team developed a specialized test for white shark eDNA and used stand-up paddleboards to collect water samples from four coastal sites beyond the surf line. Their analysis revealed white shark eDNA in two samples from known shark habitats, while the other two sites showed no traces of the sharks. This test could potentially help identify shark presence in the future and protect surfers.
"One of the aims of this research is for lifeguards to simply walk up to the shore, collect some water, shake it, and check if white sharks are nearby," said Kevin Lafferty, the study’s lead author, in a statement.
Using eDNA does have its drawbacks. Ocean currents can carry eDNA away, and the genetic material may break down rapidly in the water. "Another challenge is that eDNA could remain in the ocean for days, meaning a positive result might suggest the presence of a species that has already moved on," the researchers note in their paper. Nonetheless, they emphasize that this development is a promising step toward improving shark monitoring and conservation efforts.
