Are there too few great white sharks off California?

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It’s a mystery of the sea: How many great white sharks are prowling near California’s surf lines?

Some scientists say the population is large and healthy. Others say it is alarmingly small. No one has ever known for certain, but the question has become crucial this year.

great-white-sharkState and federal authorities are weighing a request to classify the fish scientists know as Carcharodon carcharias as an endangered species worth preserving at all costs, a step that could, among other things, wipe out what’s left of a gill net fishing industry that inadvertently snares great whites.

“This is a tough one — we are keenly aware that the scientific community is polarized on this issue,” said Adrianna Shea, deputy chief of the California Department of Fish and Game Commission.

Great white sharks are apex predators, meaning they feed at the top of the food chain and are naturally low in abundance. Few creatures possess the fearsome mystique of the white shark, which can reach 21 feet, weigh 31/2 tons and hunts near surf lines shared by surfers, scuba divers and swimmers.

The National Marine Fisheries Service and the state Department of Fish and Wildlife have been researching the health of the great white population since last year, when the environmental groups Oceana, Shark Stewards and the Center for Biological Diversity filed petitions calling for endangered species protection.

The groups were reacting to the first — and only — census of great whites ever attempted. Conducted by UC Davis and Stanford University researchers and published in the journal Biology Letters in 2011, the census estimated that only 219 adult and sub-adult great whites lived off the Central California coast, and perhaps again that many in the entire northeastern Pacific Ocean, including Southern California.

Other shark experts claim the actual population is several times larger, a legacy of state and federal laws curbing pollution, banning near-shore gill netting, protecting sharks and halting the slaughter of marine mammals they prey on.

The authors of the census study declined to comment on the merits of the petitions. However, one of the them, Sal Jorgensen, who is now a research scientist at the Monterey Bay Aquarium in Monterey, said, “I don’t think there is an imminent threat. The money being spent by the government to evaluate this issue would be better spent trying to evaluate this question: Is the number of white sharks rising or falling?”

The census was conducted from 2006 to 2008 on sharks that gather around Tomales Point, near Bodega Bay, and the Farallon Islands off the San Francisco coast from late July until late January. The researchers assumed the population is closed during the study period, meaning no sharks leave or join the group, and that it returns to the area in precise annual homecomings, making reliable census estimates possible.


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