The first sign of it was the large shadow cruising slowly and confidently beneath the ocean surface before disappearing beneath the small boat.
"Where is she, anyone see her?" Stanford researcher Barbara Block asked, as her four-member team scanned the waters off Año Nuevo State Park just North of Santa Cruz — a couple hundred yards from shore.
Suddenly, the water exploded as the head of a 16-and-a-half white shark lunged above the surface and bit down on a piece of carpet cut out in the shape of a sea lion. Researchers Going Deep to Study White Shark Populations
"We don’t know who she is, do we?" Block asked routinely as researcher Tim White jabbed a GoPro camera attached to a pole into the water near the shark, which quickly lost interest in the carpet and dove back beneath the boat.
This scene last November was typical of the months between October and February, when the sharks arrive on the Bay Area coastline and Block and her team from Stanford stake out the area, tagging the large predators with electronic transmitters as part of a decades-long study to define the shark’s population.
"So right now we're studying the white sharks here," Block said, "in order to predict their long-term population trend."
After more than two decades tagging white sharks off the Bay Area coastline, this spring the team from Stanford University, along with the Monterey Bay Aquarium, will follow the creatures to the open ocean halfway between Hawaii and Baja — an area known as the White Shark Cafe — as part of an extensive effort to unravel even more details about the sharks' mysterious lives.
"We don't actually know what happens when white sharks leave these waters and go towards the open waters of the Pacific Ocean," White said.
White sharks arrive in the Bay Area each September, stationing themselves around elephant seal breeding grounds at the Farallones Islands, Año Nuevo State Park, as well as around Tomales Point. Reaching as long as 20 feet in length, they are skilled at hunting elephant seals and sea lions.
Stanford researchers have tagged white sharks in the National Marine Sanctuaries of the Farallons and Monterey Bay for about the last twenty years — affixing them with acoustic tags that have a tracking range of about 500 meters. The tags send information to a receiver on a buoy which relays it up to a satellite and back down to instruments aboard the boat.
Over the last four months Block and her team have been especially focused on tagging sharks with long-range satellite transmitters that will enable the upcoming research expedition to track the sharks thousands of miles to their offshore domain at the Cafe — once they depart in Winter.
"We’re very excited because these tags will allow us to locate the sharks in April and May," Block said on the deck of Stanford’s research boat, The Blue Serengeti. "We’re going to have a big research ship — The Falkor — with a team of scientists from Stanford and the Monterey Bay Aquarium."
The team hopes the research at the White Shark Cafe will reveal more about which creatures the sharks interact with in the open seas, what they eat there and the threat they face from open water commercial fishing.
"So here in Año, the sharks are protected with state protections and Federal protections in the National Marine Sanctuary," Block said. "And when the sharks move out of those boundaries into the offshore waters they actually are exposed to high seas fisheries."
The extensive research in the Bay Area is ultimately aimed at determining the population of sharks that return each year to the area which ranges from Monterey to Marin Counties. Block estimates more than 220 adult and sub-adult white sharks visit the area each year. Many of the returning sharks are familiar to the researchers — bearing electronic tags from previous years, and unique physical features the team has documented through video.
"We've been able to actually keep track of these white sharks as individuals," Block said, "as animals we've come to know as personalities."
Many of the sharks get nicknames to help keep track of their identities; "Rudolph" for the white mark on its nose; "Bling Bling" for various markings and earlier tags, "Scarface" for… well, obvious reasons.
"Each white shark has a unique dorsal fin just like a human’s thumbprint," White explained. "You can tell which individual shark is based on the pattern of its fins."
The team uses a small piece of permitted bait to draw the shark to the vicinity of the carpet seal cutout. Once the sharks move in to investigate, the decoy is reeled closer to the boat where the team will attempt to insert a transmitter into the body of the shark with a long pole.
On a day-long outing last November, the team encountered more than a dozen white sharks and successfully attached tags to three of them.
The sight of a sixteen-foot shark swimming alongside a roughly 25-foot boat might seem a little jarring but the experience is more fascinating than intimidating.
"It does not ever get old tracking white sharks here along the coast," White said. "I mean when you see a 16-foot white shark swim directly underneath you, and you put an electronic tag onto the animal it is a thrilling experience every time."
When the team sets out on April 20th for a one-month high seas expedition aboard the R/V Falkor research vessel, it’ll mark the next phase of Block’s decades-long work, which also includes the study of other open ocean fish such as Blue Fin tuna as well as species like sea lions that make-up the lower level of the white shark food chain.
While the crew folded up shop after a day of tagging along the coast, Block marveled as a humpback whale breached close to the boat. She took in the orange sun folding into the Pacific, glowing somewhat at the end of a fruitful day of tagging.
"We have that privilege here in California that they come very close to our shores," she said of the sharks. "We can wake up in our houses and come out an hour-and-a-half out to sea and interact with some of the greatest animals on our planet, and it’s a really exciting place to learn about how they work."