New Estimates of the Shark-Fin Trade

[Guest guest]

New Estimates of the Shark-Fin Trade

Janet Raloff

Science News

Week of Nov. 4, 2006; Vol. 170, No. 19

 

Immense numbers of sharks each year are slaughtered for their fins—not 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 Asia—and occasional

seizures of illegal harvests elsewhere—hint 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

rs 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

rs at http://www.sciencenews.org/articles/20050604/bob8.asp).

 

Counting catches

 

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 Asia—at least through 2001—moved 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.

 

Big trade, in sometimes-small fins

 

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:

 

Some fins are consumed domestically, so they're not reflected in statistics on

international trade.

 

Some countries don't distinguish shark products in their reported statistics for

fish.

 

A black market exists in threatened or endangered shark species

 

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 time—in many cases only two to

four—and, 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

sharks—because 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.

 

Trade tracking gets harder

 

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.

 

http://www.sciencenews.org/articles/20061104/food.asp