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Giant Clams: Now you see them, soon you won’t?

by Admin-Phmp
Published: Last Updated on


By Henrylito D. Tacio

Photo courtesy of Gregory C. Ira

If the Philippines don’t watch out, it may soon lose a natural treasure thriving in its waters.

“We need to do something now before giant clams become extinct,” urges Dr. Rafael D. Guerrero III, former executive director of the Philippine Council for Aquatic and Marine Research and Development and now a scientist with the National Academy of Science and Technology.

Giant claims may not be endemic to the country, but the Philippines is one of the few countries where they thrive. These bivalve mollusks reportedly live in the shallow coral reefs of the South China Sea, West Philippine Sea, Sulu Sea, Red Sea, but mainly in the Indian and South Pacific Oceans.

Giant clams may have existed even when dinosaurs roamed around this planet. “They have been around for over 38 million years,” wrote Vicky Viray-Mendoza, the Maritime Review Magazine executive editor.

“Antonio Pigafetta, the Italian navigator who joined Ferdinand Magellan in his sea travels around the world, documented these giant clam species as early as 1521 in his journal,” Viray-Mendoza wrote.

Of the 12 species of giant clams known to man, eight can be found in the Philippines’ coral reefs. These are Tridacna gigas (true giant clam), T. deresa (smooth giant clam), T. squamosa (fluted giant clam), T. crocea (boring clam), T. maxima (elongated giant clam), T. hippopus hippopus (strawberry clam or bear claw clam), T. hippopus porcellanus (China clam), and T. noae ningaloo (Noah’s giant clam or teardrop clam).

The Switzerland-based International Union for Conservation of Nature (IUCN) has listed all of these giant clams as endangered species. In its IUCN Red List of Threatened Species, two species – T. gigas and T. deresa – as “vulnerable.” Considered rare to find is T. hippopus porcellanus. The rest are just as endangered but are misclassified as “lower risk/ conservation dependent.”

According to Viray-Mendoza, who retired as a World Bank group operations analyst and has a special interest in the marine environment, these various species of giant clams live in Palawan, Eastern Samar, Maricaban Island, Silaqui Island (in Bolinao, Pangasinan), Batangas (particularly Anilao), Samal Island (in Davao), Negros, and Tawi-Tawi.

With the help of some non-government organizations, giant clams have been restocked at the following sites: Anda, Pangasinan; Masinloc, Zambales; Calape, Bohol; Camotes Island, Cebu; Ilocos Norte; and Hundred Islands National Park.

Giant clams are described as “solar marine species,” which means they need the sun to grow, survive and thrive. According to Viray-Mendoza, giant clams live in flat coral sand or broken corals and can be found in shallow warm waters and depths up to 20 meters. 

“The giant clam gets only one chance to find a nice home,” according to a report released by the National Geographic. “Once it fastens itself to a spot on a reef, there it sits for the rest of its life.”

Serving as substrates of corals and sponges, marine biologists say giant clams – which can live in the wild reportedly up to over 100 years – help increase fishes’ residence and act as hiding places for other marine organisms.

In her in-depth report, Viray-Mendoza noticed that most of the giant clams that used to be abundant in the Philippine waters have dwindled. “Its populations are diminishing quickly, and the giant clams have become extinct in areas where they were once abundant,” she deplored.

Giant clams – which can grow up to nearly 1.2 meters long and weigh 227 kilograms – are also listed in the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES), an international agreement between governments whose aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

Giant clams are harvested for food. “Though the soft body parts account for about 10% of the body weight, it is nearly pure, healthy protein,” said Oceana, an international organization trying to protect the world’s oceans.

The meat of giant clams reportedly fetches P6,000 to P8,000 ($120 to $160) per kilogram. In Japan, where it is known as himejako, the meat is considered a delicacy. Some Asian foods include meat from the muscles of the clams. In China, large amounts of money are offered for the adductor muscle, which the Chinese think to be an aphrodisiac.

There’s some truth to the claim of being an aphrodisiac. “American and Italian researchers teamed up to analyze the bivalves, and found that clams rich in amino acids that trigger an increase in sex hormone levels,” Viray-Mendoza wrote. “Also, the giant clam’s high zinc content can aid in the production of testosterone.”

These days, giant clams are valued for their shells. Touted as the “jade of the sea,” the shells are seen as an alternative to ivory from elephant tusks. A Science feature reported these shells are sold from P150,000 ($3,000) to P600,000 ($12,000). In China, where it is a hit, they are made into carvings, jewelry, and other ornaments – “as status symbols for the wealthy and as protective charms in Chinese Buddhism.”

To save the giant clams, the government included the species in the Philippine Fisheries Code (Republic Act 8550). The Code prohibits the act of collecting, selling, and exporting giant clams. Should anyone caught violating the law, the person will be fined administratively, “three times the value of the species, or P300,000 ($6,000) to P3 million ($60,000).”

In addition, the person committing the unlawful act will be imprisoned from five to eight years and a fine equivalent to twice the administrative fine and forfeiture of species.

“Giant clams are being protected through the Marine Protected Areas (MPAs),” said Dr. Guerrero. MPAs restrict human activity for a conservation purpose, typically to protect natural resources.

Artificial spawning of giant clams has already been done by the Marine Science Institute (MSI) of the University of the Philippines at the Bolinao Marine Laboratory in Bolinao, Pangasinan.

Over 40,000 giant clams are reportedly living at the Silaqui Ocean Nursery in the said province. Late last year, the municipal council in Bolinao passed a resolution declaring the coastal town as the Philippines’ Giant Clam Capital.

In Davao Region, another success story was initiated by the Davao del Norte State College (DNSC), which manages the Marine Reserve Park and Multipurpose Hatchery at Barangay Adecor in Kaputian District in the Island Garden City of Samal.

Preservation efforts commenced in 1999 when the area was declared a marine park. It got a major boost when MSI provided the much-needed support through its Giant Claim Enhancement Program. Today, more than 2,000 giant clams are thriving in the 14-hectare marine reserve park. About 800 juveniles are currently being taken care of.

In response to the call for conservation and increasing interest among the locals and international tourists on giant clams, DNSC launched the community-based Taklobo Tours Project. It started in 2013, and now it is one of the island’s tourist destinations.

“Awesome and inspiring marine sanctuary that protects several species of giant clams,” commented one tourist. “With our snorkel masks on, we were led underwater by a certified guide to witness firsthand these amazing sea creatures. We also learned about their habitat, life cycle and feeding. A definite must-see.”

There’s still hope for giant clams, after all. “To save our giant clams, we should protect them in the wild from poachers (particularly foreigners) and promote their sea farming,” Dr. Guerrero suggested.

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