CSI on the beach: How scientists are using DNA to 'smell' for sharks around beaches
Detecting environmental DNA from white sharks could be used to make beaches safer
Researchers have found they can detect the presence of sharks around busy beaches by sampling the water for "environmental DNA" in a process that they hope can help inform beachgoers when it's safe to go back into the water.
Researchers sampled water near a popular beach area in Carpinteria, a seaside city near Santa Barbara, Calif., that white sharks have been known to frequent. They found multiple copies of white shark DNA in those test samples.
White sharks, also known as great white sharks, are responsible for most shark attacks on humans.
"All organisms are constantly shedding bits of skin or mucous or whatever," said research lead Kevin Lafferty, a marine biologist with the US Geological Survey based at the University of California, Santa Barbara.
"It's sort of an offshoot of what you might call crime scene technology, being able to sample DNA and identify it."
All of this shed material contains DNA, and it can persist and drift in the water for several days before degrading.
A drop of DNA in a big ocean
Lafferty cautions, however, that finding environmental DNA can't reveal the size or age of the sharks that are, or have recently been, in the sampled waters, nor can it indicate how dangerous they may be.
"It tells you that a shark was in the vicinity within a few days and that's about it," he said.
Still, tests like these could provide valuable information to help authorities know when they should close beaches for visitors' safety.
Lafferty imagines it being used to supplement existing shark detection methods like aerial surveys with drones, satellite tagging of sharks, and of course the sharp eyes of a lifeguard looking for fins in the water.
"One of the goals of this research is for a lifeguard to be able to walk down to the shore, scoop up some water, shake it and see if white sharks are around," he said.
Shark attacks often make headlines around the world when they happen. But while scientists insist such incidents are rare, there are some signs that they've become more frequent in recent years.
One possible reason for this, ironically, is the success of some conservation efforts. Due to reduced shark fishing, as well as population increases in their natural prey — seals and sea lions — white sharks have seen their numbers rise in recent years. The reduction in fishing pressure, in particular, has allowed these slow-reproducing animals to rebuild their numbers.
Ideally, Lafferty hopes his team's research will help minimize conflicts between people and sharks.
"The fewer shark attacks we have, the better for people and for sharks — and we can hopefully coexist peacefully with this really magnificent creature," he said.