Friday, September 16, 2011
Great white shark numbers dwindling
The world’s most feared fish may have something to fear itself: Its own demise. Far fewer white sharks are cruising the waters off California than previously thought, according to a new study. Counting the great white sharks was a hands-on activity. Researchers went out into the Pacific Ocean in small boats to places where great white sharks congregate, and lured the massive predators into photo range using a seal-shaped decoy on a fishing line.
From 321 photographs of the uniquely jagged edges of the sharks' dorsal fins, researchers identified 131 individual sharks. From these data, they used statistical methods to estimate that there are 219 great white sharks in the region.
The study, published in the journal Biology Letters, is the first rigorous scientific estimate of white shark numbers in the northeast Pacific Ocean, and represents one of the best estimates among the world's three known white-shark populations.
Great white sharks also live in the waters around Australia and New Zealand, and off the coast of South Africa.
Shark species around the globe have suffered steep declines in recent years. As many as one-third of the world's sharks and other cartilaginous fishes are threatened, and shark numbers along the United States eastern seaboard have plummeted, some species by as much as 90 percent. Great white sharks are classified as "vulnerable" by the International Union for the Conservation of Nature, but relatively little is known about the elusive species.
Is enough being done to protect the great white shark population?
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