About 200 tons of illegally harvested giant shells worth nearly $ 25 million (£ 18 million) were seized in the Philippines.
The seizure is one of the largest ever shipments of endangered species.
Four suspects have been arrested on an ecologically protected island in Palawan Province.
Huge shells can grow more than a meter and can weigh up to 250 kg. They are seen as vital to the local marine ecosystem.
The Philippines is home to most of the world’s giant tropical shellfish species.
Jovic Fabello, a spokesman for the Palawan Council for Sustainable Development, said the confiscated shells include Tridacna gigas, the world’s largest shell.
“Taking giant shells out of their natural habitat is a form of intergenerational crime,” he told AFP.
“It will permanently affect the marine ecosystem and future generations will be deprived of the benefits that flow from it,” he added.
Tridacna gigas contains seaweed, which is a food source for many of the fish species consumed by humans. They are increasingly vulnerable to poaching, both for meat and shellfish, which are used as a substitute for ivory in jewelry and decorations.
In the Philippines, killing endangered species can lead to prison sentences of up to 12 years and fines of up to one million pesos (£ 15,000).