Image Source via Getty Images
Dennis Wagner, USA TODAY
Tue, June 14, 2022, 12:19 PM·17 min read
CARPINTERIA, Calif. – The Shark Lab team is chasing shadows: dull, dark blurs that skulk in the turbid waters offshore as surfers navigate waves a hundred yards away.
The sun and fog wage their perpetual battle for control of Southern California’s coastline.
Heavy swells and a stiff breeze eliminate the prospect of spotting dorsal fins slicing along the water’s surface. A drone is launched and buzzes overhead, looking for targets.
After a minute, the pilot radios to others: “We’ve got a tagged one. Just north of the rock pile.”
It is a great white shark.
A boat moves in. Yamilla Samara Chacon leans over the bow, lowering a pole camera into the water. The shadow swirls away as she retrieves the pole and views the creature's tag on a video monitor: “A 9-footer. It says 12212, Raw B.”
The pursuit renews to get a tissue sample. The shark moves away, spooked. “I’ll see if I can be very quiet,” lab director Chris Lowe says, maneuvering the boat.
“Like a shark whisperer,” Samara Chacon laughs.
The great white vanishes into the depths. Within seconds, the drone has found another one, and the game of tag is on.
Similar scenarios play out regularly along beaches of Southern California from Santa Barbara to San Diego, where researchers locate great white sharks with remote-controlled air support. They track them with tags, underwater monitors and satellite signals. They dart them to secure muscle tissue, analyzing isotopes to learn what they eat. They gather seawater to measure DNA, calculating the concentration of sharks and prey fish.
The researchers use advanced technology not merely to track an iconic species. They're attempting to solve a mystery.
Here, along a sandy beach inhabited by Hollywood stars and frequented by tourists, nearly everyone seems to agree that great whites appear in greater numbers than anyone has seen before. They are nearly all young sharks, 4 to 10 feet long and less massive than the monster adults.
From 2017-21, California lifeguards reported a fivefold increase in great white shark sightings – nearly all of them youngsters.
Along one stretch of beach, Lowe and his team from California State University, Long Beach, encountered 40 juvenile great whites within 2 miles, hanging out in areas the researchers describe as “nurseries.”
Most researchers say the sharks don't pose a risk to humans. The question is why so many have appeared, and what it means for the future of the species, and the ocean.
Scott Fairchild, a shark enthusiast and drone hobbyist who shoots videos of young sharks swimming among people, says he can usually locate a great white within 45 seconds of launching his aircraft.
He’s given nicknames to some of the critters based on their markings: Scar Face has old head wounds, possibly from a boat propeller; Rudolph has a white nose.
Though the sharks are juveniles, the species carries an ancient allure. “They’re literally older than time,” Fairchild says with unabashed awe. “They’re actual dinosaurs.”
'Jagged teeth'
Scientists linked the modern white shark to megaladon, a big-toothed, prehistoric monster fish that plied the oceans 60 million years ago, but that theory has been displaced by findings that the great white descended later from a different species. A research paper published this year suggests the megaladon may have gone extinct because it lost a food-competition battle with white sharks.
No matter the history, great whites are the world’s largest predator fish, roaming throughout the seven seas.
Like muscle-bound torpedoes, they can hit speeds near 20 mph during an attack, preying mostly on marine mammals but also fish, birds and an occasional whale. An average adult specimen may be 15 feet long; large females sometimes exceed 20 feet and 4,000 pounds.
Even the Latin name, Carcharodon carcharias, seems ominous. (Carcharodon literally means “jagged teeth.”)
Ralph Collier, director of the Global Shark Attack File, says an adult white shark’s jaws, about 2½ feet wide, contain 24 upper teeth and 28 lower ones, each backed by seven rows of developing replacements. The main teeth fall out every two or three weeks, he says, meaning a shark might go through 30,000 during its life.
That intimidating image was brought to cinematic life in the movie "Jaws," which may have forever villainized great whites in the public eye.
In some measure, the fear they inspire is deserved: White sharks have accounted for more human fatalities than any other oceanic creature.
Yet, by scientific accounts, attacks on people are extremely rare and almost always reflect a “test bite” rather than an attempt to kill, and most victims survive. Worldwide, there are fewer than 10 fatal, unprovoked shark attacks each year.
As Collier sees it, "Jaws" unfairly maligned the creatures, though he agrees with one of its most famous lines. The marine biologist portrayed by Richard Dreyfuss described the great white as an evolutionary miracle: “All this machine does is swim and eat and make little sharks.”
The great white can smell 1 part blood per 20 million parts water.
Its head and snout are filled with receptors, known as ampullae of Lorenzini, which detect electromagnetic pulses emitted by potential prey – even a heartbeat.
A unique metabolism gives great whites a temperature roughly 15 degrees warmer than water they swim through. That provides for greater speed but requires massive calories.
Fat from mammals satisfies that need and is stored in the liver. Collier says an adult white shark’s liver may account for 30% of body mass. Filled with an oil known as squalene, it makes the fish buoyant and allows for weeks between meals.
Collier says he opened a 4,745-pound great white and found a liver weighing 1,500 pounds. Another specimen’s gullet contained 800 pounds of elephant seal.
White sharks are migratory, traveling thousands of miles in deep ocean and bearing young during spring or summer in relatively warm, shallow coastal waters. No one has witnessed a birth.
Collier notes that great whites are cannibalistic, but a hormonal release during delivery suppresses the mother’s appetite, protecting the newborn until she’s moved on.
Baby whites, about 4 feet long, remain in shallow waters along sandy beaches for the first few years, more than doubling in size as they chomp stingrays, halibut and other fish.
Researchers stress there is no way to know how many roamed the oceans in past epochs. Few attempts were made to count them, and those efforts were unsophisticated compared with the electronic tagging, drone surveillance and other technologies used today.
A prevailing theory coalesced by the 1970s that great white populations were plummeting, at least off California's coast. Human hunters and death in commercial fishing nets had taken a toll.
The danger was not just to sharks but to their food supply. Marine mammals known as pinnipeds – such as sea lions, seals and elephant seals – are a primary food for adult sharks. And their numbers had been depleted.
The crisis with pinnipeds was so dire that in 1972 – three years before "Jaws" came out – Congress passed the Marine Mammal Protection Act to conserve the animals.
In 1994, California enacted a ballot measure that prohibits the use of gill nets within state waters, 3 nautical miles from the shore. That year, the taking of great whites was banned in state waters; the prohibition was extended to all U.S. waters in 2005.
After those provisions, populations of pinnipeds are flourishing. Pacific white sharks are migratory, spending much of their lives in obscure, unprotected depths from the northern Hawaiian Islands to Mexico. What's happening with the overall population is less certain.
"White sharks are hard to study," notes Barbara Block, a Stanford University professor of marine sciences. "And we don't really understand how to protect them in that environment."
A baby shark boom?
Lowe grew up on Martha’s Vineyard, Massachusetts, where "Jaws" was filmed. Surfing and fishing drew him into marine biology, but he had no interest in studying great whites.
“They were overrated,” he says. “The prima donnas of the shark world. But then I started seeing the little ones (off California beaches), and that changed me. They’re so cute when they’re small.”
Lowe became intrigued by the number of small sharks hanging out by public beaches. Other researchers suggested great white populations in the Pacific Ocean were dwindling. Checking data from commercial fisherman who inadvertently capture sharks, Lowe found an opposite trend: The population seemed to be increasing.
“Even I was a little skeptical,” he recalls. “How can a species that everybody says is going down be coming back?”
The population question emerged as a controversy in the ichthyology world.
Twelve years ago, Block estimated there were 219 adult and sub-adult great whites off California's central coast. (For the past eight years, she's been part of a team identifying and counting specimens based on unique dorsal fin markings. Block now estimates the central California coast has a "stable and robust" population of about 300 nonjuvenile white sharks.)
In 2014, George H. Burgess, then director of the Florida Program for Shark Research, estimated there were roughly 2,000 great whites along the California coast, while a state Fish and Game study concluded the white shark population for the entire northern Pacific was somewhere between 339 and 3,000.
As more shark nurseries were detected along California's shoreline, Lowe grew convinced the population was surging.
“Thirty years ago, when I first started doing this work, hearing about a white shark along the beach was really rare,” he says.
Lowe set about identifying nurseries, counting junior sharks and trying to figure out what drew them to particular places. He's especially curious about a sandy stretch along Padaro Lane in Santa Barbara County, which drew more young sharks for more years than any other.
"Why this beach?” he asks, surveying a coastline of multimillion-dollar mansions owned by Hollywood stars.
Farther south, another puzzler: Until 2018, Lowe says, "you very rarely saw juvenile sharks in San Diego, and now they are there daily."
Lowe and the National Oceanic and Atmospheric Administration suggest that laws adopted over the past half-century to protect sharks and their main food sources may have reversed a population decline. “To me, this is actually a conservation success story,” Lowe says.
If the count is growing, when did it start and why?
To understand the dynamics, and as a safeguard for the public, California’s Legislature ponied up $3.75 million in 2018 for the White Shark Population Monitoring and Beach Safety Program, with Cal State Long Beach as the ramrod.
'Just big toddlers'
Like detectives, Lowe and students try to plot out the creatures' behavior – in part to help lifeguards keep beaches safe.
What are the sharks eating? Why have nurseries suddenly proliferated along California beaches? Why do adults sometimes bite humans but almost never consume them?
Like most researchers, Lowe finds himself thrust into a balancing act, recognizing that great whites account for more human deaths than any other oceanic creature while explaining that attacks are rare, people are not natural prey, and the juveniles pose no threat.
“They, by and large, treat people like flotsam,” Lowe says of nursery sharks. “They just don’t care. … They’re just big toddlers.”
Every day, swimmers and surfers frolic next to young white sharks, which visit waist-deep water.
In videos, the humans are mostly oblivious. Fairchild says that when his drone buzzes overhead, surfers know what it means. “They put their hands in the air like, ‘What? Where?’”
In the past decade, Lowe says, there have been five bite incidents around the nurseries. In the lone fatality, teeth impressions indicated an adult shark – not a juvenile.
In the big picture, Lowe says, great whites get a bad rap. Over the past 50 years, fewer than a dozen deaths have been recorded along California's coast. Humans kill far more great whites than vice versa, Lowe says, and far more people are injured by stingrays than by sharks.
As Lowe talks about the unknowns, it becomes clear that research discoveries create as many riddles as they solve.
The Diablo Canyon power facility near San Luis Obispo is a curious example. Seawater used to cool nuclear generators flows from the plant into a cove, creating a warm area of ocean. Lowe says tracking systems show adult great whites hang out near the plant for days, then head to the Farallon Islands for seal meals before returning.
Though researchers have not figured out the dynamics, he says, “It’s literally like an outdoor spa where they’re gathering.”
Do not harass the seals
This year, as San Diego City Council members mulled an ordinance to keep people out of a sea lion rookery in La Jolla, opponents came up with an interesting argument:
If the seals and sea lions are protected, they said, the colony will grow larger and attract sharks, which might attack tourists.
The controversy boiled over as visitors hassled the wildlife or got too close taking selfies. A Sierra Club group and others pressed for emergency shore closures, especially around newborn sea lions, for the safety of people and animals.
In a letter published by the newspaper La Jolla Light, Kurt Hoffman of Ocean Access Advocates – a coalition of divers, swimmers and surfers – contended Point La Jolla was not a natural breeding ground for pinnipeds, so white sharks hadn't been in the area. Then last summer, Hoffman claimed, he encountered 25 sharks along beaches north of the rookery.
“It may take a serious shark attack on a La Jolla Cove swimmer … to get this issue recognized,” he wrote. “That will be tragic for the family of the swimmer or diver.”
Hoffman’s letter triggered a rebuttal from sea lion protectors who accused him of using “scare tactics” while offering “misleading and inflammatory statements" with “no scientific facts for readers.”
Sierra Club critics quoted Lowe, who collaborates with the nearby Scripps Institution of Oceanography, explaining that sharks along beaches north of La Jolla are juveniles that don’t eat mammals or pose a threat to people.
Lowe says no great white sightings have been recorded near the rookery. Though the California population seems to be growing, he says, bite incidents declined even as beach recreation increased.
“Some people aren’t really looking at the science,” Lowe concludes. “We just don’t really see big (white) sharks there.”
In April, the California Coastal Commission approved San Diego’s request to protect the Point La Jolla rookery from late May to mid-September for the next seven years, during pupping season.
Fences and warning signs block access to the mammals as they sunbathe on the rocks, belching and flipping their fins. On a Friday in late May, a young man approached and began to step over the chain barrier. One of his friends urged him to reconsider.
“What, this is still America, isn’t it?” the man replied before returning to the sidewalk.
Shark attacks and facts
In 1987, Craig Rogers, 40, paddled out to catch some waves near Half Moon Bay when he noticed that his surfboard had stopped moving. It wasn’t bobbing in the waves or flowing with a current.
Rogers glanced down and found himself eyeball to eyeball with a 17-foot shark. It had gently clamped its teeth into the surfboard, missing Rogers' dangling legs. He remained frozen, aware that the area has a history of adult shark attacks, then slid into the water. The giant fish released its grip, slashing Rogers' fingers before it slipped away, a pair of teeth embedded in the board. Rogers caught a wave to shore.
Some shark experts contend that when a great white chomps on a human, it is not attacking or eating – just inspecting. “We don’t know exactly why they bite,” Lowe says. “What we do know is very few people get consumed. … At best, we think the shark has probably made a mistake.”
Collier uses the Rogers incident to explain his belief that such events are expressions of curiosity.
Great whites employ vision, smell, electronic receptors and taste to identify food, he says: “These aren’t accidents. They’re decisions a shark is making on a cerebral level to bite something. It’s investigation.”
Collier has collected data on human-shark “interactions” going back to 1900. There were 232 incidents along the coast of California, Oregon and Washington. Of those, 124 occurred in the past 22 years, including seven fatalities.
Collier says the increase is not a function of more sharks or greater aggression; it reflects a dramatic surge in human recreation.
He recalls visiting La Jolla in the 1960s and finding only a handful of snorkelers and almost no paddleboarders or kayakers. “You go down there on a Saturday now, and there’s hundreds of divers and people swimming,” he says. “There are people everywhere in the ocean today.”
Collier speculates that juvenile sharks near popular beaches grow familiar with humans, reducing the number of bites because they “learn very quickly that we’re not really anything of interest.”
Swimming with the sharks
Two Shark Lab students, Samara Chacon and Patrick Rex, set up remote underwater cameras.
Samara Chacon studies the diet of juvenile whites. Rex is researching the volume of marine recreation and how the young sharks behave when they come into contact with humans.
Other students analyze the nursery habitat and water conditions where young sharks roam and their morphometrics (length, girth, weight). A sample title: “The Role of Water Temperature and Social Dynamics in Nursing Beach Site Fidelity of the Juvenile White Shark.”
The cameras are baited with squid to attract fish, which in turn may lure sharks into view. “Think of it like video cameras on a city street,” Lowe says. “This is our version for sharks, only we’re setting ’em up with a doughnut shop.”
Cameras are plunked down beyond the surf.
Moments later, Samara Chacon dons a wetsuit and plunges into the water, swimming with great whites. She brings one end of a net to colleagues on the beach, so they can drag it in. The idea is to capture and count whatever fish the sharks may be eating. Each bit of information is a puzzle piece, helping to build a portrait of great whites – their behavior, vulnerabilities and threat.
At Santa Barbara's harbor, after fieldwork is completed, Lowe allows that, as his team tries to solve scientific problems, he's working as a PR man for one of the most maligned creatures in God’s blue seas.
“We do this because it’s really fun and cool,” he says, “but if we don’t get it out to the public … just because you see a shark, you don’t have to worry that it’s going to bite you. They really don’t seem to pay much attention to people.”
As Lowe finishes that sentence, an amphibious tour bus rolls down the harbor ramp and into the ocean, music blaring and people waving. Lowe nods toward the vessel, which has its name spelled out on the bow in giant, threatening letters: “Land Shark.”
“That’s what we’re battling, right there,” Lowe says.
For all his efforts to assure people they're safe around sharks, the mysteries persist. A few weeks after the marine fieldwork off Padaro Lane, Lowe sends an email update:
"Unfortunately, all the shark(s) left Padaro beach last week and we're not sure why "
This article originally appeared on USA TODAY: Great white sharks at California beaches: What scientists are finding
No comments:
Post a Comment