100 Million Sharks Killed Each Year

Aggressive overfishing threatens to push some shark species to extinction, and a new study puts annual shark deaths at 100 million.

"Our analysis shows that about one in 15 sharks gets killed by fisheries every year," study leader Boris Worm, a professor of biology at Canada's Dalhousie University, said in a statement. "With an increasing demand for their fins, sharks are more vulnerable today than ever before."

Based on available data for shark deaths and estimates of unreported illegal catches, the researchers estimated that 100 million sharks were killed in 2000 and 97 million in 2010. But since scientists lack sufficient data on shark catches, they say the real number of annual shark deaths could possibly be between 63 million and 273 million.

Sharks are fished for their meat, liver oil, cartilage and valuable fins, which are hacked off, often from live sharks, to be used in shark fin soup, an ancient and prized delicacy in East Asia. Since sharks have slow growth and reproductive rates, it can be tough for their populations to bounce back from big losses.

Conservationists say the depletion of shark populations is concerning because as apex predators, they help balance ecosystems in the world's oceans. (On the Brink: A Gallery of Wild Sharks)

"In working with tiger sharks, we've seen that if we don't have enough of these predators around, it causes cascading changes in the ecosystem, that trickle all the way down to marine plants," said study researcher Mike Heithaus, a Florida International University biologist.

On March 3, hundreds of delegates from 177 different countries will descend on Bangkok for the meeting of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). On the agenda will be increased trade protection for five species of sharks - the oceanic whitetip, porbeagle and three types of hammerheads - which are hunted for their fins.

"A simple vote 'yes' to support their listing could turn things around for some of the world's most threatened shark species," Elizabeth Wilson, manager of global shark conservation at the Pew Charitable Trusts' environmental organization, said in a statement today. "Countries should seize this opportunity to protect these top predators from extinction."

Sharks have a PR problem that might be hurting their chances of survival. A study out last year found that a majority of the media coverage they get involves shark attacks on humans, which doesn't reflect how rare these scary encounters are. In 2012, there were 80 confirmed shark attacks worldwide, but only seven of them were deadly, according to the University of Florida's International Shark Attack File.

The new research was detailed online in the journal Marine Policy.

More from LiveScience:

Image Gallery: Great White Sharks Cyclops of the Sea: Pictures of a One-Eyed Shark In Photos: Top 10 Deadliest Animals This article originally appeared on LiveScience. Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Shark fins drying in the sun in Kaohsiung before processing. 30 percent of the world’s shark species are threatened or near threatened with extinction.

Atlantic Halibut

April 25, 2012 -

Whole Foods, the Texas-based natural foods supermarket, no longer carries fish considered to be unsustainable. The Whole Foods ban includes fish that is either overfished or caught in a harmful way, according to their website. The popular Atlantic Halibut made the list, though the company will still sell Atlantic cod that is caught by hook and line or gillnets. "Stewardship of the ocean is so important to our customers and to us," David Pilat, the global seafood buyer for Whole Foods told the New York Times. "We're not necessarily here to tell fishermen how to fish, but on a species like Atlantic cod, we are out there actively saying, 'For Whole Foods Market to buy your cod, the rating has to be favorable.'" Here's a look at the list of fish that the superstore no longer sells and why.

Octopus Whole Foods uses ratings set by the Blue Ocean Institute, a conservation group, and the Monterey Bay Aquarium in California. The ratings are based on factors including how abundant a species is, how quickly it reproduces and whether the catch method damages its habitat.

Imported Wild Shrimp "At Whole Foods Market, we've been saying that our mission is to sell only wild-caught fish that has been responsibly caught. For a few years now, we've used color-coded sustainability ratings, from green (best choice) to red (avoid), to help you make an informed choice. Now we're putting our mackerel where our mouth is: To support greater abundance in our oceans, we're no longer carrying red-rated wild-caught seafood!" the company wrote on its blog.

Tuna (from specific areas and catch methods rated "red") On their website, Whole Foods says that they stopped selling "species that were extremely depleted in the oceans, such as orange roughy, shark and bluefin tuna" years ago. The company uses the sustainability ratings of the Marine Stewardship Council (MSC).

Rockfish According to the Monterey Bay Aquarium, "In recent years, reduced fishing has allowed many rockfish populations to recover from low levels. Gear concerns remain, however -- trawl-caught rockfish should still be avoided."

Swordfish Some of the gear used to fish swordfish "accidentally catches sea turtles, seabirds and sharks," according to the Monterey Bay Aquarium.

Skate Wing Skates are in the overfished category. Most are also caught with bottom trawls, which result in high levels of accidental catch.

Sturgeon According to Monterey Bay Aquarium, "Sturgeon farmed in the U.S. is a good alternative to most wild sturgeon, whose populations have seriously declined due to overfishing for sturgeon eggs (caviar)."

Tautog Also known as black fish, Tautog are considered a "vulnerable" species. They are found close to shore on hard-bottom habitats, occasionally entering brackish water.

Trawl-Caught Atlantic Cod Fishermen often catch cod with bottom trawl, large nets that skim across the seafloor. Trawling, according to the Monterey Bay Aquarium, "damages marine habitats and produces bycatch."

NEWS: Can We Save the Tastiest Fish in the Sea?

Turbot A cousin of Pacific halibut, turbot are a right-eyed flatfish -- as they develop, their left eye migrates across the top of the skull toward the other eye on the right side. Turbot are yellowish or grayish-brown on top and paler on their underside.

NEWS: Oceans’ Fish Could Disappear by 2050

Gray Sole Gray sole, a flatfish bottom-dweller, has experienced heavy fishing pressure from domestic and international fleets over the last half-century, according to Monterey Bay Aquarium.

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