The Great White Count

sharks_intro

By Joel Hersch | Photos courtesy of Pelagic Shark Research Foundation

The quest among researchers to better understand the Pacific’s great white shark population stirs debate

For surfers in California, there is a feeling of deep reverence that comes with knowing that one of the ocean’s top predators, the great white shark, is liable to be patrolling the waters beneath some of their favorite breaks. And with that reverence, there is also a huge relief in not knowing it when they are—treating the shark’s presence as a kind of abstraction is a saving grace.

Professional surfer and Santa Cruz Waves founder Tyler Fox has knowingly surfed sharky breaks his whole life, but after watching a tall, dark triangular fin cut through the water 30 feet away at Davenport Landing 10 years ago, he says he hasn’t been able to surf that particular spot again.

A surfer’s knowledge that the odds of experiencing a shark attack are extremely low feeds an out-of-sight, out-of-mind mentality. But, according to white shark researchers, the fact that there is a very low probability of getting chomped does not necessarily correlate with a small population.

Photo: Callaghan Fritz-Cope

Photo: Callaghan Fritz-Cope

While their numbers were very low in the past due to fishing and habitat infringement, George Burgess, director for the Florida Program for Shark Research, says that the animals have made a major recovery in the last 100 years. The Marine Mammal Protection Act of 1972 helped by allowing the seal population to grow, bolstering the great whites’ food source.

Additionally, it became illegal in California waters to hunt great white sharks in 1994 and illegal by federal law in 1997. Due to these and other factors, “We’ve seen a slow and steady increase,” Burgess says.

However, until three years ago there was no comprehensive data on the species’ population, and when population research was first published in 2011, it sparked more questions than it answered. In the three years since, a series of scientific assessments and re-assessments on the white shark in the North East Pacific has fueled a heated debate around their true population size and whether the animal, which is already listed as a “protected” species, warrants further protection under the Endangered Species Act.

The data that began it all was in a 2011 paper by Taylor Chapple, a post-doctoral scholar at Hopkins Marine Station in Pacific Grove (a Stanford University lab), that recounted a three-year study on adult and “sub-adult” white sharks at three Central California aggregation sites: Año Nuevo, Tomales Point, and the Farallon Islands. Using a mark and recapture approach and a variety of statistical methods, Chapple’s team determined the Central California white shark population of their study group to be 219. The team calculated that the whole North East Pacific, which spans from Alaska, south to Mexico and west to Hawaii, has a population of 438 adults and sub-adults, though Chapple says that the North East Pacific’s entire population is likely much larger than this.

Photo: Sean Van Sommeran

Photo: Sean Van Sommeran

However, about a year after his findings came out, Chapple’s paper spurred environmental groups Oceana, Shark Stewards, and the Center for Biological Diversity to petition the National Marine Fisheries Service (NMFS) and the California Department of Fish and Wildlife (CDFW) to evaluate the white shark for endangered species status. This prompted an extensive 18-month study, says Karen Grimmer, the resource protection coordinator for the Monterey Bay National Marine Sanctuary. Following the population reviews, both of which came out in June, state and federal researchers determined white shark numbers along the California Coast were closer to 3,000 and did not warrant endangered species status.

“They determined that there wasn’t enough [of an] issue with the abundance of white sharks to list them as endangered,” Grimmer says.

One of the reviews was led by Burgess and his 10-member team of scientists, who started their re-assessment of the white shark population in 2013 using Chapple’s data and a different statistical method to calculate the population for a larger area, and published their findings in the journal PLOS ONE on June 16. They found that the North East Pacific is populated with approximately 2,400 white sharks.

Their research was based exclusively on Chapple’s aggregation sites and did not include habitats in Mexico and other parts of the West Coast and migration between various sites, says Gregor Cailliet, a scientist and professor emeritus with Moss Landing Marine Laboratory and co-director of the Pacific Shark Research Center, who worked on the study alongside Burgess. This means that the entire North East Pacific population, across all size classes, could be closer to 10,000, he says. Although, Burgess says that this number is not rooted in their scientific findings.

Meanwhile, Chapple feels that the media and his fellow researchers have heavily misconstrued the scope of his team’s 2011 data.

“Our data is very specific to Central California and our specific size class,” he says. “They’re talking about all of California and all size classes, which we don’t have data for. It’s an inappropriate comparison.”
One of Cailliet and Burgess’ key issues with the original data was how conservation groups leveraged it.
Cailliet believes some conservation groups possess ulterior motives in their push for new endangered species classifications.”

Photo: Caterina Gennaro

Photo: Caterina Gennaro

“It brings them attention and more money,” he says. “As a result, people who are running these organizations can be overly aggressive … I think it’s unnecessary for an organization to use data that are not 100 percent convincing and costs the government millions of dollars to write reports that deny [a] petition.”
While he does see value in the research papers that ultimately came from the petitions, Cailliet says the problem becomes a “bio-political or socio-economic issue—a waste of money.”

Once the conservation groups submitted the Endangered Species Act (ESA) petitions, backed with Chapple’s research, the state and federal governments were required to allocate substantial resources and time, which means those resources and time were re-directed from other, possibly more deserving, areas.

“Certain species that are in need of recovery and endangered species status have lost the funding, so there’s a very explicit loss that occurs when a species is petitioned unnecessarily,” says Burgess. “We have to be very careful in the biological world not to overstate the severity of a problem because there are ramifications.”
While the white shark population appears to be much larger than what it was interpreted to be back in 2011, Chapple says a subsequent misunderstanding occurred when media portrayed Chapple’s initial assessment of 219 and Burgess’ re-assessment of 2,400 this year to mean the white shark population had sky-rocketed by almost 2,200 animals.

“Thinking those two things were related whatsoever was completely inappropriate,” he says. “That’s probably been the most frustrating part.”

Chapple says there is no hard data on whether the population has gone up or down.

“Our paper in 2011 is pretty clear that the data we collected are a single point, and we have to build on that—you have to start somewhere with a baseline,” he says. “You can’t tell a trend in three years, [but] as you get more data you can start to build that trend, and that’s what we’re doing.”

Cailliet, however, says that while there is not enough numerical data to say if the population is rising, white shark activity does indicate a slow population rise. Those assessments are based on incidental by-catch in fishermen’s gillnets off Southern California, and the number of white shark attacks, which have both increased.

There have been 44 shark attacks on humans along the California coast in the last seven years, according to sharkattacksurvivors.com, four of which were fatal. As of press time, there had been just one this year, the July 5 nonfatal attack on swimmer Steve Robles at Manhattan Beach in Los Angeles. In that case, a 7-foot white shark was hooked on a wharf fisherman’s line and thrashing in distress as Robles swam by.

Photo: Sean Van Sommeran

Photo: Sean Van Sommeran

But Chapple says to exercise caution when interpreting attacks as an indication of white shark numbers.

“With attacks on pinnipeds or human interactions or fisheries catches, the causality of those things is not a direct result of population changes,” Chapple says. “It can be behavior, water temperatures, the number of people and seals in the water, time of year, or the observations.”

Cailliet explains that, because data on the population did not even exist until three years ago, what researchers do have is still immersed in murky waters.

Grimmer points out that the white shark is an exceptionally difficult creature to study: “It’s very elusive, they don’t come up to the surface all the time, they’re fast, and they travel incredibly long distances in short amounts of time.”

She says researchers are just beginning to scratch the surface of understanding the white shark.
“From what we do know,” she says, “there are probably white sharks in the water [around people] quite often, but attacks are still extremely rare.”

Of attacks on humans, Burgess says surfers pay the highest price. But he marvels at the way surfers think about the ocean and its dangers. Of the hundreds of shark-attack surfer victims he has interviewed, he says almost every one of them has retained a positive attitude about sharks and returning to the water.


Read more from Vol 1.2 or Subscribe to SCW Magazine!


Guest Author


Leave a Comment