Giant clams are the largest mollusks on Earth. Unlike other mollusks, once they fasten themselves to a spot on a reef, there it stays for the remainder of its life. Giant clams generally live in the warm waters of the South Pacific and Indian Oceans.
Colloquially they are known as “man-eating clams” and are certainly large enough to swallow a human. However, the giant clam is not one bit interested in eating men or women for that matter. What they do eat mostly is sunshine. That sunshine nourishes the many algae that live in their tissue on the sugars and other metabolic resources which are by-products of photosynthesis. Clams feed on sugars and other metabolic resources which are by-products of photosynthesis.
According to Wikipedia, giant clams are the members of the clam genus Tridacna which are the largest living bivalve mollusks. There are actually several species of “giant clams” in the genus Tridacna, which are often misidentified as Tridacna gigas, the most commonly intended species referred to as “the giant clam”.
Tridacna gigas is one of the most endangered clam species. Antonio Pigafetta documented these in his journal as early as 1521. One of several large clam species native to the shallow coral reefs of the South Pacific and Indian Ocean, they can weigh more than 440 lb., measure as much as 120 cm (47 in) across and have an average lifespan in the wild of over 100 years. They are also found off the shores of the Philippines and in the South China Sea in the coral reefs of Sabah (Malaysian Borneo).”
Giant clams are generally found in flat coral sand in relatively shallow water up to 66ft. The maxima clam has the largest geographical distribution among giant clam species; it can be found off high or low-elevation islands, in lagoons or on fringing reefs. During the day, the clam keeps its shell open to receive the maximum amount of sunlight it needs to photosynthesize.
In a relationship that benefits the clams and protects the algae, the clam feeds on the nutrients they filter out of the water. They filter out a variety of organic debris and zooplankton. They can live in clear nutrient-poor waters and murky turbid waters. This filter helps clean the environment. Filtering is also the way they broadcast eggs and sperm to feed other reef animals.
Their survival is threatened by overharvesting. The adductor muscle of the giant clam is sought after as a delicacy. Their shells are sought after as decorations, and they are being used for scrimshaw and carving. The giant clamshell is now considered by some artists to be the “Jade of the Sea”.
University of Hawaii Sea Grant Fellow Mara-Biggs wrote, “My graduate thesis at Hawaii’s Institute of Marine Biology is to assess the evolutionary relationships of giant clams to other species (phylogenetics) and the population structures of these magnificent creatures to better understand and protect them.
Giant clam populations have plummeted for a variety of reasons, but the aquarist trade is a large reason for the decline. They are also harvested for their meat and their massive shells are collected for use in scrimshaw work which sells for high prices. In recent years, prices paid to fishermen have jumped 40-fold. One uncarved clamshell that used to be worth about $300, is now worth $12,000. This high market value has increased fishing pressures on the clams, which are already susceptible to overharvesting. There is a push to list giant clams under the endangered species act, and countries have closed some giant clam fisheries. But poaching still occurs here, as seen from a $25 million poaching bust earlier this year.”
In the western Pacific Ocean, there are hundreds of islands called the Palau Islands. There are some of the oldest known giant clamshell middens. Many of the myths associated with giant clams originated before Christianity with the Palauan religion. Archaeologists reason the earliest islanders actually depleted the giant clam population, but they realized what was happening and may have taken measures to conserve the giant clams. Ancient Palauan conservation law was known as “bul”, which prohibited the taking of giant clams during the critical spawning period or when conditions indicated overharvesting.
Pacific islanders used the giant clam shells as ceremonial containers for ancestral skulls or ritual washing vessels. When giant clam shells were brought back to Europe by explorers, they were prized as baptismal founts. In the early 1tth century, French King Francois I was presented with what would become the most famous pair of giant clam shells in a church, by the Republic of Venice.
According to Cynthia Barnett, writing in Atlas Obscura, “Luxury demand for the adductor muscle meat and the ivory-like shells has driven Tridacnas extinct in China. Taiwan and other parts of their native habitat. Some of the toughest marine protection laws in the world, along with giant-clam aquiculture pioneered here, have helped Palau’s wild clams survive. The Palau Mariculture Demonstration Center raises hundreds of thousands of giant clams a year, supplying local farmers who sell to restaurants and the aquarium trade and keeping pressure off the wild population. But as other nations have wiped out their clams, Palau’s ocean territory is an increasing target of illegal fishers.”
It is estimated that poachers have been hauling up half a million clams a year for the last 40 years before regulations and increased policing slowed the poaching. However, the poaching still continues. The shells have become as sought after as clam meat. The shells are becoming fashionable for bathroom sinks and have long been venerated by considering them one of the seven treasures of nature.
Giant clams are eaten raw with lemons or sometimes simmer in coconut milk for a soup, they are made into pancakes, cooked sliced or sautéed. YouTube offers videos on how to prepare and cook giant clams.
The giant clam is an incredible gift from nature. The variety of colors from various species is dazzling. The sheer size is amazing considering the size of its close cousins. Despite the major efforts of conservationists, there is the ever-present danger that the giant clam will become extinct. One thing is for sure, you need never fear being eaten by a giant clam.