In the past three years, shark attacks have increased 25 percent worldwide, according to an International Shark Attack File report, yet recent findings prove that the numbers of adult great white sharks off the coast of California and Baja California, Mexico, are alarmingly low.
Here in Half Moon Bay, which is part of a region known as the Red Triangle extending off the coast from Bodega Bay out slightly beyond the Farallon Islands and down the coast to Big Sur, shark sightings and attacks have been reported over the years despite the populations of great white sharks dwindling.
In 2005, Half Moon Bay surfers Tim West and Chris Loeswick surfing Mavericks escaped the bite of what was determined to be a a 12- to 14-foot, one-ton white shark. And a number of shark sightings have been reported on SurfPulse at Linda Mar in Pacifica over recent years.
Still, great white sharks are on the brink of extinction because of their low population size and the ongoing threats they faces from human activities.
“It's tragic for sharks, and tragic for the ecosystem,” writes John McCosker, a great white shark expert and chair of the Department of Aquatic Biology at the California Academy of Sciences. “Sharks are top-level predators for the ocean ecosystem. And the oceans are collapsing. When the sharks go, there are no controls,” says McCosker. “If there are no sharks, there are no safety checks.”
Tens of millions of sharks are being killed each year for the Asian sharkfin soup market. Their fins are hacked off and the sharks are dumped back into the ocean to die.
"As a keystone predator at the top of the food chain, and as a "k-selected" species with extremely low reproductive rates for a fish (4-11 pups every other year), older age of first breeding, and dependence on high survival rates, the white shark is extremely vulnerable to any extra man-assisted mortality and should be protected," said Peter Pyle, a biologist with the Institute for Bird Populations who did shark research working for the Point Reyes Bird Observatory from 1980 to 2003.
As a result of the shark's vulnerability, Oceana, the Center for Biological Diversity, and SharkStewards filed a scientific petition with the National Marine Fisheries Service in Washington D.C. seeking to protect the U.S. West Coast population of great white sharks under the Endangered Species Act.
This week, they will also seek protection under California’s Endangered Species Act. An Endangered Species Act listing will afford the sharks protections from key threats and garner funding for research to better understand the status and threats to this distinctive population of white sharks.
“The new science set off alarm bells for all of us, as no one expected the population to be so dangerously low,” said Oceana’s California program director, Dr. Geoff Shester. “Great White sharks are powerful allies keeping our oceans healthy, and they need us to protect them far more than we should fear them.”
Great white sharks found off the U.S. West Coast are part of the Northeastern Pacific population, genetically distinct and isolated from all other great white sharks around the globe. In 2011, new scientific studies produced the first population estimates of West Coast adult and sub-adult great white sharks, together totaling fewer than 350 sharks — far lower numbers than researchers expected, presenting an inherently high extinction risk. The continued existence of white sharks is also hampered by their low reproductive output, slow growth rate, late maturity, and high mortality rates during the first year.
"When we proposed protection of the white shark in California in 1994 (California AB 522) we had 24 user groups comment on the bill and all 24 were in favor of protection, including surfers, kayakers, and divers. The Surfrider Foundation was one of the strongest supporter. We argued that a healthy white shark population would keep the seal and sea-lion populations in check, which would in turn help our salmon and halibut fisheries, and I believe that this has indeed occurred," said Pyle.
Deadly gillnets capture and kill great white sharks, and are presently the leading threat to their survival. While their direct capture for sale is prohibited off the coasts of California and Mexico, young great white sharks are killed as incidental bycatch in commercial fishing. Set and drift gillnets, which together target California halibut, white sea bass, thresher sharks and swordfish, are responsible for over 80 percent of the reported young white sharks caught in their nursery grounds. These fisheries have very low observer coverage, meaning more white sharks are caught than what is reported.
“The fierce great white shark is no match for gillnets that are like curtains of death for marine animals. There are so few of these majestic sharks left in our waters, they urgently need protection,” said Catherine Kilduff, attorney for the Center for Biological Diversity.
Young great white sharks off the Southern California coast are also found to have the second highest mercury level on record for any sharks worldwide, six times higher than levels shown to cause physiological harm to other ocean fish species.
In addition, these sharks had the highest levels of the contaminants PCB and DDT in liver tissue observed in any shark species reported to date globally.
“These majestic predators are vital for the health and balance of our ocean ecosystems,” said David McGuire, director of SharkStewards. “Even the removal of one sexually mature individual from a population this small can have serious impacts on the population as a whole. They need stronger protection immediately.”
— Information courtesy of SharkStewards. Additional reporting by Christa Bigue.