Giant clams, a keystone marine species, can live for several decades and reach significant sizes.

However, across the Indo-Pacific, several species of these reef animals, including the iconic true giant clam, Tridacna gigas , have been driven almost to extinction in the last few decades. This has been through a combination of habitat degradation, harvesting for meat and shells and declining coral reefs.

Today, Fiji is trying to reverse years of decline by breeding giant clams in captivity and releasing them back into the sea.

While considerable efforts have been made so far to boost numbers, a key question remains: can rebuilding a species in hatcheries translate into long-term functioning wild populations?

Why Giant Clams Matter So Much To Reef Health

Giant clams are crucial to reefs due to their role as filter feeders and ecosystem engineers. They host millions of microscopic algae in their tissues, and also release them, along with nutrient-rich waste and mucus, which feed fish and other reef animals.

They can siphon hundreds of gallons of water daily, cleaning it and removing excess nutrients, which helps prevent harmful algae blooms.

“They also produce calcium carbonate, one of the main building blocks of coral reefs. As they grow, their shells contribute to the reef’s structure, helping to strengthen and stabilise it over time,” Alisi Soderberg, marine biologist at Kokomo Private Island, told Forbes in an email.

She added: “They also form part of the food chain, providing prey for predators such as octopus. When their shells are eventually empty, they become valuable habitats for a variety of other marine species.”

These species can include crabs, small fish and sponge, among others.

Due to their ability to accumulate particles and respond quickly to changes in water quality and temperature, scientists often use them as indicator species to monitor overall reef health and conditions.

Giant clams also help in carbon sequestration and help the ocean buffer against climate change.

As such, their decline means much more than losing just one species and can severely weaken the resilience of tropical oceans to global warming as well.

In the last few decades, overfishing, habitat loss and climate pressures have led to the decline of over 80% of the global Tridacna gigas population, according to a 2024 assessment by the University of Colorado Boulder.

The animals are heavily prized in Asian cuisine, with their shells being used to make jewellery and statues in many cases too. Due to them being completely stationary and living in shallow, clear, tropical waters, they are also entirely defenseless against human poachers.

Similar to coral reefs, giant clams are also vulnerable to bleaching due to marine heatwaves, along with ocean acidification.

They also have a very slow reproductive cycle, taking 10 to 12 years to reach maturity, which can make it even harder to replace numbers.

Tridacna gigas has currently been reclassified as Critically Endangered, from a previous Vulnerable status by the International Union for Conservation of Nature (IUCN). Local extinctions have also been recorded in New Caledonia, Taiwan, Thailand and Singapore.

How Fiji Is Bringing Giant Clams Back

Fiji’s Ministry of Fisheries is attempting to boost giant clam numbers through a blend of breeding programmes, ocean nurseries and marine protected areas. These efforts are supported by local communities, universities, resorts and international conservation partners.

The Makogai Mariculture Research Centre acts as a primary breeding and spawning facility, raising infant and juvenile clams like Tridacna gigas and Tridacna maxima before they are released and distributed across the islands.

Resort and community partnerships are another important tool, with projects like the Tavarua Island Giant Clam Restoration Project uniting the Ministry of Fisheries, the University of the South Pacific (USP) and local resorts in setting up protected cages and ocean nurseries.

For Kokomo’s giant clam farming programme, juvenile clams are supplied by the Ministry of Fisheries.

“Once they arrive at Kokomo, we place them into protective cages fitted with settlement slabs, where they can attach themselves and begin growing in a safe environment. Releasing healthy giant clams back onto the reef is one of our primary measures of success,” Soderberg said.

She added: “We also monitor the presence of naturally occurring juvenile clams on the reef as placing mature clams together increases the likelihood of successful fertilization and natural recruitment.”

Seeding and relocation are another part of Fiji’s approach. Juvenile clams and reproductive mates are being transported from research stations to protected lagoons and reef sites, such as Gau Island, Vorovoro and Tavarua to rebuild self-sustaining wild populations.

Fiji is also taking key legal and regulatory steps to ensure that the progress it has made to support giant clams so far remains protected. The Fiji Fisheries Act enforces strict harvesting rules, while outright banning the export of giant clam meat.

Local communities have also established no-take marine reserves, further supporting conservation efforts.

In March 2026, researchers from the Ministry of Fisheries recorded a 100% survival rate in Tridacna Maxima seeds released in Vorovoro, with specimens growing three to four times their original size.

The Challenges That Remain

Although Fiji has made remarkable progress in bolstering giant clam numbers, some key hurdles remain.

“One of the most challenging stages comes early on, as the juvenile clams are extremely small and can take time to firmly attach themselves to the settlement slabs. Before this happens, strong weather or rough conditions can easily dislodge them from the cages,” Soderberg noted.

She added: “Even as the clams grow larger, they remain vulnerable. They continue to be protected within cages because natural predators, such as octopus, can prey on them, while illegal harvesting by humans also remains a threat.”

Another major challenge is coastal development, which can increase sedimentation and pollution. This can cloud the water and degrade coral reefs, while smothering young clams.

Marine heatwaves, caused by rising water temperatures, remain another hurdle, as they lead to bleaching, due to clams expelling the crucial symbiotic microalgae living in their tissues.

Some maritime regions both within and outside Fiji may also have weaker enforcement, which allows poachers to continue targeting wild populations, despite bans.

In other cases, breeding programs that grow and reintroduce juvenile clams into the wild may struggle with low juvenile survival rates. Maintaining marine hatcheries and nurseries, especially on remote islands can also be very expensive due to high logistics costs.

One of the biggest issues, however, is that while Fiji can potentially produce more clams, healthy reef ecosystems, which are dependent on a much wider range of factors, are essential to their long-term survival and growth.

Towards Healthier Giant Clam Populations

Fiji’s attempts to actively rebuild giant clam populations through breeding programmes, ocean nurseries and targeted partnerships highlight how conservation can move beyond simply protecting endangered animals to actively rebuilding lost populations.

However, wider challenges like climate change and poaching pressures can make it harder to ensure that enough juvenile clams end up reaching maturity.

Long-term community and habitat protection will therefore be critical in determining whether hatchery-reared clams can survive long enough in the wild to reproduce and establish self-sustaining populations.

If successful, Fiji’s approach could also offer a valuable model to help other small island nations in restoring critically endangered marine species.