Web edition: November 1, 2006
Immense numbers of sharks each year are slaughtered for their finsnot meat, just their fins. This harvest helps feed a growing appetite throughout Asia for a popular soup, one with snob appeal comparable to that of caviar. Indeed, a single bowl of shark-fin soup can cost $100 in a high-end Hong Kong restaurant.
The key ingredient of shark-fin soup is cartilage, which after hours of simmering, takes on the appearance and texture of cellophane noodles. Fleets harvest fins at sea by catching almost any variety of shark, slicing off all the animal's fins, and throwing the then-helpless fish back into the water.
This brutal practice, outlawed in U.S. waters (see Shark Finning Faces Broader Sanctions) is not regulated on the high seas or in most nations' territorial waters. Fins can command $200 a pound in Asian markets, whereas shark meat yields fishing fleets no more than one percent as much revenue per pound.
The huge arrays of fins for sale in markets throughout Asiaand occasional seizures of illegal harvests elsewherehint at the magnitude of the "finning" enterprise. However, estimates of the actual number of sharks killed for the soup market have been based upon data that were sketchy at best.
Because conservationists need to quantify the threat of finning to slow-growing shark populations, Shelley C. Clarke of the Imperial College London has spent several years infiltrating fin auctions in Hong Kong. From the data she gleaned on fin numbers, types, sizes, and source species in the market, she and her colleagues have estimated the degree to which international trade in fins is propelling potentially unsustainable harvests of these top-predator fish.
In the October Ecology Letters, Clarke's team estimates that finning claims between 26 million and 73 million sharks annually. That number doesn't even account for sharks killed for meat (SN: 4/15/00, p. 246: Available to subscribers at http://www.sciencenews.org/articles/20000415/fob6.asp), sport, and natural medicines (SN: 3/5/05, p. 154) or as incidental by-catch of fishing boats targeting other species.
Nevertheless, the unprecedented market-based data show the range of shark ages and species being targeted, says Clarke. They also indicate which populations are most vulnerable to extinction and show that continuing observation of harvests and fin auctions is essential to understanding why shark populations have been dwindling so rapidly in recent years (SN: 6/4/05, p. 360: Available to subscribers at http://www.sciencenews.org/articles/20050604/bob8.asp).
Clarke focused her analyses on fins moving through Hong Kong auctions for several reasons. Her previous studies had established that about half the shark fins sold in Asiaat least through 2001moved through Hong Kong traders. Also, although she's a U.S. citizen, Clarke is a permanent resident of Hong Kong and able to establish working relationships with traders there.
One trader invited her into an auction, normally a closed, secretive affair. After going the first time, says Clarke, "I refused to take the hint that I shouldn't keep going." Ultimately, she notes, she attended 17, "until they threw me out. Then I basically had to take the hint."
Another trader, she says, "took pity on me when I mentioned that although I had been able to watch what was happening [at those auctions], I didn't know how many bags of fins and of which type were being sold." So, after she agreed to shield his identity, the trader opened up a drawer "and gave me 18 months of his auction records," Clarke says. "That was a gold mine" and turned out to be critical to the calculations behind many of her team's new estimates.
Clarke also obtained slivers of more than 700 dried fins. These samples, from fin stocks of 28 different traders, allowed her group to do genetic analyses and correlate the Chinese names for various categories of fins with specific shark species. Ya Jian, for instance, means blue sharks (Prionace glauca). Chun Chi refers to either of two types of hammerheads belonging to the Sphyrna genus. Wu Yang corresponds largely to the silky shark (Carcharhinus falciformis) but also to species with similar fins. And traders use the term Hai Ching when referring to any of a host of coastal species with black-tipped fins.
One cooperative trader even let Clarke borrow a bag of fins from a warehouse so that she could take measurements of the typical size and weight of fin being sold. Being trusted with the fins was a "coup," says Clarke, since a single fin could have a value of $100.
Clarke's group eventually focused on trade statistics for 11 Chinese categories of shark. These were categories containing only a small number of well-defined species.
The researchers used these assorted data and more from other scientists to calculate the harvest weights of the dried fins in the marketplace. From those numbers, the researchers estimated the sizes, weights, and ages of the animals from which the fins had been removed.
Clarke's computations indicate that the soup market may claim as many as 73 million sharks each year. However, she points out, even the median of her group's range of estimates, 38 million sharks, translates into an estimated 1.7 million metric tons of dead sharks.
That tonnage is more than four times what the United Nations Food and Agricultural Organization has estimated as the annual slaughter of sharks for their fins.
Clarke suspects that even her numbers are lower than the real harvest. Factors suggesting that even more sharks are killed annually:
Indeed, Clarke says that one Hong Kong fin trader recently told her, "I think the real [fin] trade is three times what you estimated."
A disturbing fact gleaned from the Hong Kong auctions, the researchers say, is that many of the fins being traded come from immature animals. Unlike most fish, sharks may take up to 20 years before they reproduce for the first time. Moreover, sharks bear few young at a timein many cases only two to fourand, typically, only every few years or so. Harvesting sharks before they've reproduced limits the chance that already depleted shark populations will recover.
"Traders will tell you that they want to catch only mature, large sharksbecause they have bigger, more valuable fins," Clarke says. However, she told Science News Online that she commonly saw fins at auction that were only an inch long.
Traders won't even pass up fins from sharks yet to be born. Clarke says that in Taiwan she witnessed pregnant hammerhead sharks being cut open and the fins sliced off the fetuses inside.
The new Ecology Letters paper focuses on data for fin trading between 1996 and 2000. Since that time, tracking the trade has gotten harder, Clarke notes, because of changes in China, the granddaddy of fin markets.
Since 2001, when China entered the World Trade Organization, fin traders have increasingly dealt directly with markets on mainland China, not through Hong Kong middlemen.
The mainland not only has many more ports of entry for fins than Hong Kong does, but its record keeping for fin sales is not as detailed as Hong Kong's. China also imposes a duty on shark fins, which Hong Kong doesn't. So, Clarke notes, "right there you have a reason for them [Chinese traders] to underreport their activities."
Moreover, since 2001, China has allowed frozen shark fins to be reported as frozen shark meat. The first year that this rule was in effect, China's fin imports "suddenly fell by half and have stayed kind of flat since then," says Clarke. Yet, she argues, no one would have predicted that demand for the fins would diminish or even level off, because China's booming economy means more people than ever can afford the luxury soup.
Data on shark harvests have always been poor. What the new trends suggest, Clarke says, is that "if we're going to have any hope of managing shark populations, we're going to need far better data." In particular, she says, there is a growing need for observers on fishing boats and for more comprehensive trade figures on sharks. The observers, she says, are needed to begin collecting reliable, international data on where sharks are being caught, their size, their maturity, and their species.
If you would like to comment on this article, go to the Food for Thought blog.
Shelley C. Clarke
Division of Biology
Imperial College London
Silwood Park Campus
Manor House, Buckhurst Road
Ascot, Berkshire SL5 7PY
2004. International commission adopts U.S. proposal for shark finning ban. U.S. Department of Commerce/National Oceanic and Atmospheric Administration press release. Nov. 23. Available at [Go to].
2002. NMFS announces final rule to implement the Shark Finning Prohibition Act. National Marine Fisheries Service press release. Feb. 11. Available at [Go to].
Baum, J.K., and R.A. Myers. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecology Letters 7(February):135-145. Abstract available at [Go to].
Myers, R.A., and B. Worm. 2005. Extinction, survival or recovery of large predatory fishes. Philosophical Transactions of the Royal Society B: Biological Sciences 360(Jan. 29):13-20. Abstract available at [Go to].
Raloff, J. 2005. Empty nets. Science News 167(June 4):360-362. Available to subscribers at [Go to].
______. 2005. A fishy therapy. Science News 167(March 5):154-156. Available at [Go to].
______. 2004. Shark finning faces broader sanctions. Science News Online (Dec. 11). Available at [Go to].
______. 2002. Clipping the fin trade. Science News 162(Oct. 12):232-234. Available at [Go to].
______. 2002. No way to make soupThirty-two tons of contraband shark fins seized on the high seas. Science News Online (Sept. 7). Available at [Go to].
______. 2000. New protection for much-dogged shark. Science News 157(April 15):246. Available to subscribers at [Go to].
______. 1999. Skate-ing to extinction? Science News 155(May 1):280-281. References and sources available at [Go to].
Ward, P., and R.A. Myers. 2005. Shifts in open-ocean fish communities coinciding with the commencement of commercial fishing. Ecology 86(April):835-847. Abstract.
Watts, S., et al. 2001. The End of the Line? Global Threats to Sharks. San Francisco: WildAid. Available at [Go to].
Further information about sharks is available at [Go to] (Pelagic Shark Research Foundation), and [Go to] (American Elasmobranch Society).