Preyed Upon by Humans, Sharks Near Extinction

By Barry Estabrook
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vonlohmann/flickr


Julia Baum's official title is Postdoctoral Associate for Ecological Analysis and Synthesis at the University of Santa Barbara. Her nieces and nephews simply call her a sharkologist.

Baum should issue an audience advisory before she discusses her research: Caution, studying the oceans' great predators is seriously depressing business. "For 400 years, sharks have evolved in the oceans," Baum said on a panel at the Monterey Bay Aquarium's Cooking for Solutions symposium last week. "Now, they could be wiped out in the bat of an evolutionary eyelash."

Caught for meat, unintentionally as bycatch in the long-line tuna fishery, and as the prime ingredient in the burgeoning fin trade, shark populations are in collapse everywhere humans fish for them. Nearly 75 million sharks are "finned" each year, their carcasses thrown back into the sea, to satisfy demand from producers of shark-fin soup, who pay more than $100 a pound for the fleshy appendages. Once a rare luxury item, the soup is now eagerly slurped up as a status symbol by the rapidly expanding Chinese upper and middle classes.

Baum's research has produced some mind-boggling statistics. The population of oceanic white-tip sharks, considered the most common large species on earth as recently as 1960, has dropped by 99 percent in the Gulf of Mexico (and that was before the oil spill). Populations of smooth hammerhead and bull sharks off the East Coast of the United States have also declined by 99 percent. Looking at all shark species in the northwestern Atlantic Ocean, Baum found that the healthiest populations were down by 40 percent. The least healthy were down 90 percent or more.

"Our oceans are being emptied of sharks and the problem is global," she said. Currently, the International Union for Conservation of Nature and Natural Resources (IUCN) lists 11 shark species on its Red List of threatened species.

According to Baum, killing off top predators like sharks can also set off a cascading environmental collapse that is detrimental to the entire ecosystem—and to humans who wish to exploit its resources. She noted that with shark populations drastically reduced off North Carolina, cownose rays, a favored food item for sharks, have flourished. But the rays feed on shellfish, and their increased numbers have caused a 100-year-old scallop fishery in the area to disappear.

"Shark fishermen are like roving bandits, serially depleting populations in every ocean," Baum said. Currently, there are absolutely no regulations governing shark fishing in the open ocean. This spring, the Convention on International Trade in Endangered Species (CITES) missed an opportunity to reverse the declines when it flatly refused to give even a modicum of protection to scalloped hammerhead sharks, oceanic white-tip sharks, porbeagle sharks, and spiny dogfish sharks.

To study what an ecosystem would look like with its big predator populations intact, Baum has been forced to take her field research to Christmas Island, "the end of the world," in her words, located in the Pacific Ocean 4,200 miles from Sydney, Australia. There, she is able to study pristine reefs whose beauty and complexity make popular Caribbean reefs look like empty urban lots.

But those reefs are not likely to be spared for long. The local government has plans to resettle a large number of residents from neighboring atolls to Christmas Island. If history is any guide, when humans come in contact with sharks, the great marine predators will suffer.

This article available online at:

http://www.theatlantic.com/health/archive/2010/05/preyed-upon-by-humans-sharks-near-extinction/57381/