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Clams have long been prized as a delicacy and sometimes even as a currency. Native peoples of California used beads carved from clamshells for trade—which is likely how “clams” became slang for “money.” In the 21st century, the CLAM is a digital currency related to bitcoin. But the flesh of these bivalves is often more valuable to human stomachs than their shells and digital namesake are to our wallets. Here are five of the world’s most coveted clams.
Geoduck (Panopea generosa)
Once considered subpar chowder clams in their native Pacific Northwest, Pacific geoducks have become a hot commodity in the Asian market. Geoducks can live over 150 years and weigh as much as a house cat. A large, live clam can fetch as much as US $300 in China, where it is served in hot pots or other culinary creations. This hefty price tag has dragged geoducks into a dark underworld; in Washington State, poachers collect clams during clandestine nighttime forays and make off with thousands of dollars worth of shelled loot.
Giant clam (Tridacna gigas)
To sushi fans, the world’s largest clams are also hugely delicious. Overharvesting from the 1960s to ’80s led to severe declines in South Pacific populations, but aquaculturists in Hawaii, Asia, and Australia are attempting to farm these enormous bivalves, which can grow to be bigger than a household dishwasher. Though the clams are filter feeders, they get much of their nutrition from symbiotic algae in their tissues—which makes cultured giant clams perhaps the only photosynthetic farm animals. The sale of wild giant clams is illegal in most nations, but in Asia a single clam may fetch US $450 on the black market.
Warty Venus clam (Venus verrucosa)
Found in pockets along the coasts of Europe and Africa, these clams got their unappealing English name from the wart-like lumps on their shells. The Italians named them according to their flavor, christening them tartufi di mare or “truffles of the sea.” The French, who call them praire, serve them steamed with white wine, baked with herbs and garlic, or in a traditional bouillabaisse. Praire cost about US $10 to $18 per kilogram.
Blood clam (Tegillarca granosa)
Unlike most other clams, blood clams have hemoglobin in their blood, which helps them live in oxygen-poor environments. The hemoglobin gives a red tint to their “liquor,” and their unique, bloody appearance has lent the bivalves cachet among North American fans of “raw bars” and ceviche. Blood clams are also unusual in that they filter much more water than typical bivalves—up to 40 liters per day—which makes them more likely to pick up hepatitis and other diseases from polluted water. It is illegal to sell Asian blood clams in the United States due to health concerns. Lemon-sized clams that are imported legally from North and South America are worth US $1.50 to $2.50 apiece.
Toheroa (Paphies ventricosa)
Endemic to New Zealand, once-abundant toheroa clams were canned and shipped around the globe after Edward, Prince of Wales, praised them during his 1920 visit to the country. The population plummeted, forcing authorities to end the commercial harvest in 1969. Now only the Maori can legally harvest the clams in small numbers. Some claim that the strong, sweet, fishy taste of toheroa has turned respectable citizens into criminals. New Zealand journalist, fisherman, and cook Noel Holmes notes that otherwise honorable men “have crept over the sand hills in the dead of night and stealthily raided the toheroa beds with all the desperate daring of wartime commandos.” Fines for poaching toheroa can reach US $1300.