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The Great White Debate

by Brendan Bane

Aug. 8, 2013—The great white shark—long an object of terror and fascination—has made an undeniable comeback since its populations plummeted in the mid-20th century. But as of a couple of months ago, there is still a debate as to whether the ocean’s greatest predator faces the threat of extinction.

When the National Oceanic and Atmospheric Administration decided in late June that the West Coast great white shark was not in danger of extinction and did not deserve protection under the Endangered Species Act, the announcement was met with relief from one side of the debate and disappointment from the other.

The dispute pivots on wildly divergent estimates regarding the number of great whites plying the West Coast of North America—so-called Northeastern Pacific (or NEP) great whites—a genetically distinct and somewhat isolated subspecies.

A 2011 study by scientists from UC-Davis and Stanford, published in the journal Biology Letters, came to an unsettling discovery: the number of adult and sub-adult white sharks clocked in at just over 200, a shockingly low count.

While the authors cautioned that their research spanned a short time interval and may not have captured fluctuations in the great white population, environmental groups immediately called on both the state and federal governments to protect the sharks.

NOAA responded by launching an intensive status review, during which a specially appointed team of scientists known as the Biological Review Team would thoroughly consider all the best available science concerning Northeastern Pacific great whites and craft their own population estimate.

The NOAA/BRT team came back with an estimate indicating the population to be at least 3,000 strong—15 times greater than that of the UC-Davis/Stanford study.

NOAA scientists inferred through multiple lines of evidence that mature, “reproductively relevant” females alone totaled around 200. From that number they extrapolated that the whole population was at least 3,000.

Now that the federal government has spoken, it will be up to California officials to decide whether great white deserves protection here.

It Began with A Picture

The current battle over the great white’s political status began when researchers at UC-Davis demonstrated that individual sharks can be reliably identified using pictures of their dorsal fins, much like a person’s fingerprint. The study focused on the NEP white sharks that regularly revisit sites along the California coast.

"These animals appear again and again at very specific areas," said shark ecologist Salvador Jorgensen, one of the paper’s authors.

That proved West Coast great whites to be a confined population in the Northeastern Pacific, and set the stage for Jorgensen and his team to conduct a census of the population.

Using the techniques they pioneered, the UC-Davis team was joined by researchers from Stanford University to conduct the great white count—the first attempt at documenting the size of the population. After sifting through hundreds of photos, they were only able to document 130 individuals. They then inferred through statistical analysis that the population included only 219 mature and sub-adult individuals.

The finding sparked two petitions, which were authored and led by environmental advocacy groups Oceana, WildEarth Guardians the Center for Biological Diversity and Shark Stewards. Each petition called for the NEP population to be recognized as an endangered species under both California’s and the federal government’s Endangered Species Act.

Dr. Heidi Dewar, fisheries research biologist of the Southwest Fisheries Science Center, was appointed to head the Biological Review Team so NOAA could respond to the petitions. Dewar’s team reviewed a massive body of evidence, covering information from satellite tracking studies to DNA analyses. One year after the petitions were filed, the BRT team concluded the review and came to a surprising verdict.

“Multiple lines of evidence all pointed to a larger population than suggested by the [UC Davis] study,” Dewar said when I spoke with her earlier this week.

Dewar and her team came up with another important conclusion: By assessing additional white shark dorsal fin picture studies, records of attacks on marine mammals, and unintentional catch records from net fisheries, they reasoned that the populations were actually increasing.

Other scientists agreed that the West Coast great white population is on an upswing. Shark biologist Dr. Chris Lowe, of California State University–Long Beach, cites numerous causes for the white shark’s recovery, from stringent legislation to ecological shifts.

“Frankly,” Lowe said Thursday, “I find it quite remarkable. In the 1960s we were discharging raw sewage directly offshore along the California coastline. Water quality was very poor, resulting in significant changes in marine communities. Now California has the best wastewater treatment and strictest water quality regulation that exists anywhere in the world. As a result, fish communities are charging back.”

Lowe also credits recovered populations of marine mammals—resulting from government regulation—as a reason for the sharks’ recovery.

“As the result of the Marine Mammal Protection Act and Magnuson-Stevens Act, most marine mammals populations have recovered better than biologists could have ever imagined. Obviously, this has helped the white shark population. But it has taken decades to start to see the benefits.”

Dr. Russ Vetter, director of Fisheries Resource Division of the Southwest Fisheries Science Center and a member of Dewar’s team, agrees that the UC-Davis study alone was insufficient evidence from which to base the endangered species designation.

"They did something theoretically sound, but they were only able to do it for two to three years. We looked at a suite of scientific studies covering decades.”

Taylor Jones of WildEarth Guardians, one of the petitioners for endangered status, is unhappy with the result but appreciates the amount of science the petition inspired.

“We were disappointed by the decision,” Jones said Thursday, “but were pleased to see the amount of new research that was conducted and the interest in the shark that the petitions spurred. We hope that continues and that we continue to learn about and monitor these great predators to ensure their health and continued existence.”

Ashley Blacow of Oceana remains equally optimistic and says she is determined to continue rallying for the designation.

“Despite this unsettling federal decision, the fight to protect great white sharks is far from over,” Blacow said via email. “For many imperiled species, the battle to secure federal Endangered Species Act protections has taken many years, and Oceana will continue to use all available tools to protect white sharks until we are convinced they are safe from extinction.”

Biological Review Team member Vetter points out that the decision is not carved in stone, and should the evidence ever suggest a change, Northeastern Pacific great white sharks may be federally recognized as an endangered species.

“If more information becomes available, in particular from Mexico, or if the conservation environment changes, or more adult females are killed, the status of white sharks can and should be revisited.”

While the federal decision has been made, at least for now, the white shark may still receive endangered species designation from the California Fish and Wildlife Commission. Other animals, like the Mojave ground squirrel, are recognized as endangered through the state, but not the federal government. The NEP sharks may draw a similar fate.

Back in March, California Fish and Wildlife announced that it was considering the great white as a candidate for endangered status—the first time a marine animal was granted candidate designation under the state Endangered Species Act. That bestows the same degree of protection that fully endangered species receive. That status expires in early 2014 unless the state decides to make the designation.

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