Having the Shark Fin Soup? Think Twice

Aug. 2, 2007 — World demand for shark fin soup has resulted in a marine ecosystem domino effect that is reducing shellfish numbers to the point where an American soup favorite, clam chowder, is now under threat, according to a Current Biology paper published earlier this month.

Fishermen and diners alike are feeling the consequences.

The demand for shark fin soup "has not only left once economically valuable bivalve fisheries in crisis, but has precipitated an ecological and culinary bankruptcy," explained Andrew Brierley, the paper's author.

Brierley, a marine ecologist at the University of St. Andrews, Scotland, added that "in many East Coast eateries, the famous clam chowder is resoundingly off the menu."

The relationship between shark fin soup and clam chowder has to do with nature's predator-prey balance. When shark populations are thriving, they eat other related species, including skates and rays. Such prey eat bivalves, so more skates and rays means fewer shellfish.

Brierley analyzed findings gathered by world-renown Dalhousie University fisheries biologist Ransom Myers, who died earlier this year, just three days before his groundbreaking work on shark-dominated ecosystems was published in the journal Science.

Myers found that intentional hunting of sharks, primarily for the Asian delicacy shark fin soup, along with unintentional shark deaths due to fisheries bycatch, has led to up to 98 percent declines for tiger sharks, scalloped hammerhead sharks and blacktip sharks along parts of the East Coast.

"With fewer sharks around, the species they prey upon — like cownose rays — have increased in numbers, and in turn, hordes of cownose rays dining on bay scallops have wiped the scallops out," said Myers' colleague Julia Baum.

Brierley believes many other bivalves — including the hard-shelled Quahog clam — have suffered sharp population drops, due to large skate and ray populations.

Oysters too could soon be off certain restaurant menus, since cownose rays feed on them as well.

In the Chesapeake Bay alone, the burgeoning cownose ray population could now be consuming 840,000 metric tons, or close to 2 billion pounds, of bivalves annually, according to the Current Biology paper.

In sharp contrast, fishermen in Virginia and Maryland only caught 300 tons, or around 661,380 pounds, of shellfish in 2003. This, Brierley calculated, is "a much lower catch than the historic norm."

Although the shark loss has already begun a marine ecosystem collapse, Ellen Pikitch, executive director of the Pew Institute for Ocean Science, remains hopeful that a solution could still be within reach.

"These unforeseen and devastating impacts underscore the need to take a more holistic ecosystem-based approach to fisheries management," she said.

Brierley, who supports Pikitch's view, thinks "the grand challenge for marine science is to progress from the apparently interminable documentation of ecosystem decline to establishment of robust management policies."

Such conservation strategies, he said, would be a fitting tribute to Myers and his life's work, which was directed at preserving sharks and other marine species.