Published March 09, 2011
It may be safer than you think to go back in the water.
A first-of-its-kind census of the great white shark population in California's waters revealed startlingly few of the toothy terrors. According to the study, which tallied sharks based on photographs of their fins, there are just 219 adult and young adults in the entire northeast Pacific Ocean.
"Once we went out and noticed that we were seeing the same sharks every year, it started to dawn on us that this population isn't huge," UC Davis doctoral student Taylor Chapple, the study's lead author, told FoxNews.com.
The study, published Wednesday in the journal Biology Letters, is the first rigorous scientific estimate of California's white shark numbers -- yes, that's the fearsome finned beast of "Jaws" fame -- and the best estimate among the world's three known white-shark populations (the others are in Australia/New Zealand and South Africa).
And the number was startling, even to the researchers.
"This low number was a real surprise," Chapple said. "It's lower than we expected, and also substantially smaller than populations of other large marine predators, such as killer whales and polar bears."
There are thousands of killer whales, however, and only a few hundred sharks, even though they occupy a similar spot in the food chain, he noted.
"Based on filling the same niche, and relative metabolic budget of these animals, one might assume that they'd be somewhere in the same ballpark," he said.
Chapple explained that white sharks are currently classified as vulnerable, not endangered or critically endangered. The surprisingly low numbers may lead to a revision of that statistic, but without a baseline for the giant predators, it's impossible to say whether that number is too low or just right, he noted.
"We just don’t have a set expectation for this type of predator," he told FoxNews.com. When the study is redone next year, they'll be able to compare against this baseline.
To count sharks, the researchers went out in small boats to places where they congregate. They lured the sharks into photo range using a seal-shaped decoy on a fishing line. From 321 photographs of the uniquely jagged edges of white sharks' dorsal fins, they identified 131 individual sharks.
From these data they used statistical methods to estimate that there are a mere 219 adult and sub-adult white sharks in the region. (White sharks are classed as sub-adults when they reach about 8-9 feet in length and their dietary focus shifts from eating fish to mostly marine mammals. They are adults when they reach sexual maturity – for males, that is about 13 feet long; for females, it is about 15 feet.)
Satellite tagging studies have demonstrated that white sharks in the northeast Pacific make annual migrations from coastal areas in Central California and Guadeloupe Island, Mexico, out to the Hawaiian Islands or to the "White Shark Café," a region of the open ocean between the Baja Peninsula and Hawaii where white sharks have been found to congregate – and then they return to the coastal areas.