While traveling in Fiji as a Protector of Paradise, I had the unique opportunity to learn about Giant Clams. In this post, I share with you some giant clam fun facts and how Fiji is saving these endangered species!
I went to Fiji not really expecting to learn about mollusks but the opportunity presented itself when we went on board the Captain Cook Cruises’ Reef Endeavour.
On our third day cruising in the northern parts of Fiji, specifically in the Lomaiviti group of islands, we stopped by the island of Makogai. The island used to be the home to over 300 lepers from 1911 to 1969. But what was even more interesting for me was learning that Makogai is now a Mariculture Centre for the giant clams.
What are Giant Clams?
The giant clam is the largest living marine bivalves typically found in tropical coral reefs. Giant clams are members of the Subfamily Tirdacninae which can further be classified into two genera: Tridacna and Hipppus.
Here is a list of the 12 giant clam species found all over the world:
- Tridacna gigas– true giant clam
- Tridacna derasa– southern giant clam or smooth giant clam
- Tridacna mbalavuana (tevoroa)- devil clam
- Tridacna squamosa– fluted giant clam
- Tridacna squamosina (costata)
- Tridacna maxima– Small giant clam
- Tridacna crocea– boring clam,
- Tridacna noae (ningaloo)- Noah’s giant clam
- Tridacna rosewateri
- Tridacna lorenzi
- Hippopus hippopus – Bear Paw Clam
- Hippopus porcellanus– China Clam
The giant clam species can be found in reefs throughout the Indian Ocean, Pacific, and parts of South Africa.
Within the reef, giant clams like embedding in sandy substrates typically within 20 meters from the surface. They stay within those limits because beyond that depth, the algae they depend on to survive won’t have enough sunlight to grow.
The giant clams, specifically the biggest species Tridacna gigas, may reach up to 1.5 meters (6 feet) in length. Not only are they big in size, but they can weight up to 200 kilos (440 pounds).
Aside from its massive structure, the giant clams also get a lot of attention because of their brightly colored mantle tissue. The fleshy part of the giant clam is usually golden brown, yellow, or green, mixed with spots of blue and indigo.
Why are Giant Clams Endangered?
The giant clams in all its beauty are over-harvested by humans.
They are now listed as endangered species under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Unfortunately, though they are big, the giant clams remain defenseless against humans. Giant clams cannot even flee or swim away, which makes them easy targets for exploitation.
The shells are considered precious and can be sold for thousands of dollars. Giant clam shells are the ocean’s equivalent to an elephant’s ivory tusk. In China, they are made into carvings and jewelry as a symbol of wealth.
The giant clam’s meat is eaten by the locals as part of their diet. And in some countries, the giant clams are considered delicacies so there is a huge demand for them.
The aquarium trade has also taken part in the over-harvesting of the giant clams. Collectors love having these beautiful creatures in their artificial reefs.
In various countries like the Philippines, Indonesia, Malaysia, Australia and Fiji, the populations of wild giant clams are declining rapidly because of the demand for giant clams.
The Fijians harvest it for their shell and aquarium trade. And vasua (the Fijian word for giant clam) apparently is very delicious, especially when prepared with coconut milk.
Because of overexploitation, the Tridacna species remain endangered in Fiji and in the rest of the world.
Why are giant clams important?
As a country that heavily depends on the ocean, Fiji recognized that if they do not act quickly their way of life could be endangered as well. They knew the giant clams need to be protected and saved.
Because giant clams play a vital role in reef-building.
The giant clam’s tough shells are great for coral reef formation. They are also great as a natural habitat for smaller creatures.
As filter-feeders, the endangered giant clam can siphon hundreds of liters of water in a day. In doing so, they are able to keep algae growth in check, they remove plankton and organic matter. This important role can prevent the overpopulation of some species.
For instance, giant clams can filter the thousands of microscopic spawns of the crown of thorns (COTs) starfish. The lack of giant clams could lead to a COTs outbreak. This is not good because one crown of thorns starfish can eat up to six square meters of coral per year. So just imagine how damaging it is when those thousands of COT spawns grow to adulthood and feed on the reef.
Basically, the endangered giant clams are essential in keeping the ecological balance of the reef.
What is Fiji doing to save the giant clams?
Makogai Island Mariculture Centre
As early as the 1980s, Mokogai island became a breeding ground for the giant clams in Fiji. Because of the low population of giant clams they actually had to import Tridacna gigas from the Great Barrier Reef. The current Tridacna gigas we see in Fiji today are offsprings of these imported giant clams.
Editor’s Note: There is conflicting information about the existence of Tridacna gigas in Fiji. During my trip to Fiji we were told they were extinct. But after further research, some say that T. gigas was never there to begin with and it was only introduced in Fiji in the 1980s. You can read more about it in this CITES document.
The endangered giant clams are bred onshore then transferred to the shallows of Dalice Bay, right in front of Makogai Island. The old metal hospital beds, that were used by the leper colony, now serve as barriers to protect the juvenile clams while they are growing in the ocean.
Once they are large enough, the giant clams are transferred to other reef areas around Fiji. Hopefully, these mature giant clams are able to repopulate on their own once they are transplanted.
A giant clam can release many millions of eggs in its lifetime. They can live up to 100 years old. If they are not taken from the reef, they could make a new generation of giant clams, wherever their new ocean home in Fiji may be.
While the initiative was originally an Australian-funded project, the Fiji government recognized the importance of saving the endangered giant clams. So in 2011, Makogai Island officially became a Mariculture Centre that focuses on the restoration of the giant clams and saving other endangered species in Fiji.
With the efforts of the Fijians working in the Ministry of Fisheries, the Tridacna gigas, as well as the other endangered giant clams, are continuously being reintroduced into Fiji’s reefs.
Tavarua Island Resort Giant Clam Nursery
Because of the successful set up in Makogai Island, Tavarua Island Resort, also built their own giant clam nursery.
Tavarua in the Mamanuca Islands is notably known for two things: as one of the world’s premier surf destination and its island that is shaped like a heart.
I, on the other hand, know it as the island that has a big heart for the ocean. A few days before I left Fiji, we visited Tavarua Island Resort and learned more about their own giant clam project.
As a resort that values sustainability, they knew they had to do their part in keeping Fiji’s oceans healthy. They invested in their own giant clam nursery so they can grow giant clams and help build the reef around the island.
A few hundred meters off the coast of Tavarua Island, they established a marine sanctuary and placed metal enclosures as part of their nursery. The cages are mean to protect the juvenile clams from predators, both sea creatures and humans alike.
With the help of The Fijian Government, Department of Fisheries, Mokogai Research Facility, Tavarua Island Resort has successfully grown Tridacna gigas, Tridacna maximas, and Tridacna derasas.
Tavarua’s endangered giant clam restoration project has been essential in protecting and rehabilitating Fiji’s reefs for future generations.
Tokoriki Dive Resort Giant Clam Project
In another part of Fiji, Tokoriki Diving based at Tokoriki Island Resort has also been doing the same conservation efforts for the giant clams.
Also with the help of Fiji Ministry of Fisheries, a Tokoriki Giant Clam Regeneration Program was born.
Since their giant clam nursery began in 2000, they now host the largest collection of mature Tridacna gigas in Fiji!
The clams can be visited and enjoyed by divers in two different dive sites. You can find the Tridacna gigas, Tridacna squamosa, T. derasa and T. maxima in the protected areas.
Hopefully, these species regenerate not just around the resort but also across the western side of Fiji where they are located.
How do Giant Clams Reproduce?
Giant clams are simultaneous hermaphrodites- producing both eggs and sperm. Giant clams release their eggs, then their sperm into the water column. However, they are only able to reproduce with other giant clams that are close by through external fertilization.
After spawning, any fertilized eggs will float on the ocean for twelve hours. The eggs will hatch soon after and the resultant larva will develop an appendage that allows it to move along the ocean floor. Eventually, they will settle on the reef where they will permanently live.
The baby giant clam has to deal with the many dangers of the ocean. They could end up in areas where it is not conducive to grow. They could be eaten by predators like tiny snails, eels, octopus.
Then, the giant clams need six to seven years before it reaches sexual maturity. By that time, they will also have to deal with humans.
Basically, life is tough for clam.
This is why Fiji’s giant clam conservation projects are so important. Creating a safe and controlled environment gives the giant clams a higher chance of survival.
Aside from these giant clam breeding projects, the giant clams are protected under the Fiji Fisheries Act. This prohibits the export of giant clam meat.
Yes, the giant clams are still being consumed and harvested in Fiji. They are still endangered. But we should not lose hope.
Fiji proves that when the government and private sector working hand in hand towards a common goal, you can achieve amazing things.
With the stricter implementation of the law, growing awareness among the consumers, and conservation projects such as these, there may yet be
Tridacna maxima favorable outcomes for Fiji’s giant clams!
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What do you think of the Giant Clam Nursery Projects in Fiji?Do you know of other similar Giant Clam Conservation Projects like this in your own country?
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