Great white sharks swimming to extinction?

The world's first detailed count of great white sharks has found these marine predators may be even more endangered than previously thought. The count, which focused on great white sharks off Central California, determined that only 219 adults and juveniles exist in waters there, according to a new Royal Society Biology Letters paper. Since this region is thought to support one of the largest populations of these sharks, the outlook for great whites elsewhere is now also grim. "These findings should be used to inform further assessment of the IUCN Red List categorization of white sharks," lead author Taylor Chapple, a University of California at Davis researcher, told Discovery News. The Red List, created by the International Union for Conservation of Nature and Natural Resources, currently classifies great white sharks as being "vulnerable." In the future, the sharks could be classified as "endangered" or "critically endangered" if other counts support Chapple and his team's findings. The present study was conducted from 2006 to 2008 at two known shark aggregation sites in Central California: Tomales Point and the Farallon Islands. The researchers attracted sharks to vessels using a seal-shaped decoy and a small piece of bait. Once a great white shark approached, digital images of its dorsal fin were snapped from either above or below the water. Great white shark dorsal fins are analogous to a human fingerprint. Each one is unique for a particular shark. "Differences can be present in the general shape (i.e., triangular fin, rounded fin), but the most telling of the differences is along the trailing edge of the fin," Chapple said. "Each fin has a unique arrangement of notches, cuts, and/or flat sections. We have found that these characteristics are conserved over very long periods of time, at least in mature and sub-adult white sharks." Once shark numbers were estimated based on the images, the researchers used additional information from a database, along with math models, to come up with the 219 figure. Although no one knows precisely how many white sharks existed in the region years ago, population counts for other top marine predators are much higher. The scientists point out that killer whales in a smaller range number 1,145, while polar bears from the Southern Beaufort Sea have been estimated at 1,526. "Differences can be present in the general shape (i.e., triangular fin, rounded fin), but the most telling of the differences is along the trailing edge of the fin," Chapple said. "Each fin has a unique arrangement of notches, cuts, and/or flat sections. We have found that these characteristics are conserved over very long periods of time, at least in mature and sub-adult white sharks." Once shark numbers were estimated based on the images, the researchers used additional information from a database, along with math models, to come up with the 219 figure. Although no one knows precisely how many white sharks existed in the region years ago, population counts for other top marine predators are much higher. The scientists point out that killer whales in a smaller range number 1,145, while polar bears from the Southern Beaufort Sea have been estimated at 1,526.