By Henrylito D. Tacio
The country’s waters are teeming with biological diversity (biodiversity). Unfortunately, some of the marine species thriving in them are now being threatened; some of them in fact are facing extinction.
Imagine the children’s children of today’s younger generations may no longer see those species in their original habitat. Worse, some of them may already be extinct so that future generations get a glimpse of these species only in photographs and films.
Such is the case of the giant clams, locally called taklobo. They are the iconic residents of coral reef ecosystems. They serve as habitat for fish, invertebrates and other marine organisms.
Giant clams are not facing extinction yet, but the Switzerland-based International Union for the Conservation of Nature (IUCN) listed them as vulnerable species as their population has declined by least 50%.
To halt giant clams from becoming extinct, the University of the Philippines Marine Science Institute (UP-MSI) introduced giant clam cultures in the 1980s, where cultured giant clams were restocked around the country.
Giant clams are harvested for their shells and meat. (Winston Plaza)
Taklobo Tours
The Island Garden City of Samal was one of the areas where the said program was initiated. In barangay Adecor of Kaputian District, the protected sanctuary houses over 3,700 giant clams.
The Marine Reserve Park and Multipurpose Hatchery, as it is called, is under the supervision of the local government unit of IGACOS. It is now a project of the Davao del Norte State College (DNSC).
The DNSC is partnering with Adecor United Fisherfolk Organization to save the giant clams from becoming extinct in the area. They believe that one of the best ways to stop people from harvesting the giant clams is to educate them the importance of the species and how they help the fishing industry.
That’s how the Taklobo Tours Conservation Tourism and Livelihood Opportunities for Coastal Communities came to be. It was officially launched in 2013 but closed during the pandemic. It was reopened early this year.
The two-hour Taklobo Tours includes an hour of snorkeling in the area. Visitors are brought by means of a motorized banca from the seashore to the floating cottage, where they are oriented about the importance of giant clams. The carrying capacity of the docking area is 30-35 persons while only 10-15 persons are allowed in the viewing deck.
After giving some instructions, the visitors are told to wear a life vest and given snorkel and mask to those who are interested. Then, they swim to the area where the giant clams are perfectly arranged on the seabed. As the water is clear, they can see the endangered species up close. Touching the giant clams is strictly not allowed.
Taklobo Tours is now one of Samal’s most popular activities for tourists. “Awesome and inspiring marine sanctuary that protects several species of giant clams,” commented one tourist who has visited the place. “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.”
Before they can visit the restricted area where the giant clams are being raised, tourists need to attend a lecture first to know the importance of giant clams and what they need to do when they are on the waters. (Henrylito Tacio)
Empowering the fishers
DNSC officials said the 14-hectare giant clam sanctuary helps empower and capacitate locals to become tourist guides and conservation warriors. “The success of the program proves that responsible tourism can flourish in a protected area for environmental conservation,” they said.
Joel Gonzaga, a member of the organization, agrees. “We raise awareness by informing the people who come how endangered these giant clams are and that there are now laws regarding its preservation,” he said. “It is now prohibited to harvest them and there are some consequences if they do so.”
When the program started, there was resistance from the community as giant clams had long been a source of food and income for most of them. With Taklobo Tours becoming popular, they are happy that they have supported the initiative.
The Samal marine sanctuary is just one of the beneficiaries of the Giant Clam Stock Enhancement Program of UP-MSI. So, whatever happened to others? To answer this question, the Department of Science and Technology (DOST), through the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) funded a giant clam program to revisit these restocking sites.
Aside from assessing the current clam diversity and abundance, the program also aimed to advance culture and rearing protocols for giant clams through the use of modern molecular approaches.
This is the place where tourists are oriented before they can go into the water. (Henrylito Tacio)
Giant clams of the Philippines
There are actually 12 species of giant clams and eight of them can be found in the Philippine waters. The giant clams, known in the science world as Tridacna gigas and considered the true giant clam, can grow larger than 4 feet across and weigh more than 180 kilograms.
The seven other species are: Tridacna deresa (smooth giant clam), T. squamosa (fluted giant clam or “hadgdan-hagdan”), T. hippopus (strawberry clam or “kukong-kabayo”), T. crocea (boring clam), T. maxima (elongated giant clam), T. hippopus porcellanus (China clam), and T. noae ningaloo (Noah’s giant clam or teardrop clam).
The assessment conducted by the DOST-PCAARRD funded study showed that the 8 species are still found in the country’s waters. Surveys from 2018 to 2021 revealed high densities of restocked giant clams at several study locations where natural recruits of giant clams were also detected in 4 out 8 restocking sites.
“The presence of T. gigas recruits indicate that restocked clams are naturally spawning and producing new giant clams that may eventually grow into adults,” wrote Patrick C. Cabaitan, Roger G. Dolorosa, Girley S. Gumanao, and Cecilia G. Conaco in their collaborative report, “Giant Clams in the Philippines: Prevailing in a changing ocean through research and conservation.
“While giant clams are still prevalent in the Philippine reefs, their overall abundance and diversity remain low,” the four authors wrote. “Overharvesting, poaching, habitat destruction, and bleaching remain among the major challenges against the giant clam populations.”
The researchers have found some areas which are still home to an abundant and diverse community of giant clams. “The presence of giant clams and juveniles suggests that local recruitment is successful,” they contend.
Not "killer clams"
Giant clams are the largest living bivalves. Despite their classic movie depictions as “killer clams,” there are no reliable cases of people being trapped and drowned by giant clams. Generally, they occupy coral reef habitats – typically within 20 meters of the surface. They are commonly found in shallow lagoons and reef flats and are characteristically embedded in sandy substrates or those composed of coral rubble.
Giant clams also provide shelter for different organisms. 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 the residence of fishes and act as hiding places for other marine organisms.
“Like most corals, some anemones, and other reef organisms, giant clams utilize a combination of methods to obtain food,” explains Oceana, an international group focused solely on protecting the world’s oceans. “The majority of their energy is derived from symbiotic algae living within their cells, providing the clams with excess energy that they make via photosynthesis.”
In return, “the algae have a safe to live and receive the nutrients necessary to photosynthesize. The giant clams provide those nutrients by filtering feeding small prey from the water above the reef surface, which it siphons through its body. The beautiful, bright colors characteristic of individual giant clams is actually a result of the symbiotic algae.”
As giant clams cannot literally move due to their heavy weight (as much as 250 kilograms), they reproduce via external fertilization, where eggs and sperm are released into the water column at the same time. Although they are hermaphrodites, they cannot self-fertilize. “They are able to reproduce with other individuals that are close by,” Oceana explains.
Prehistoric marine mammals
Giant clams may have existed even during the time when dinosaurs roamed around this planet.
“We need to do something now before giant clams become extinct,” urges Dr. Rafael D. Guerrero III, a fishery expert and an academician with the National Academy of Science and Technology (NAST).
Dr. Guerrero, however, believes there’s still hope for giant clams. “To save our giant clams, we should protect them in the wild from poachers (particularly foreigners) and promote their sea farming,” he suggested.
Photos by Henrylito Tacio and Winston Plaza
Senator Bong Go
