The only beach in Hong Kong where the intertidal bivalve Meretrix cf. meretrix occurs predominately is at Tong Fuk Miu Wan on the southern coast of the island of Lantau. Tong Fuk Miu Wan and its partner, more sheltered, beach Shui Hau Wan are by virtue of their orientations separated from each other in terms of their physical form and hydrodynamics. Tong Fuk Miu Wan is more exposed to wave action arising in the South China Sea, and Shui Hau Wan is more protected from such an incursion. Meretrix cf. meretrix is an inhabitant, almost exclusively, of Tong Fuk Miu Wan because of the unique hydrodynamics of its wave-exposed beaches.

This paper aims to describe the biology and functional morphology of M. cf. meretrix in the context of its habitat and ecology. Based on the study of a sample of M. cf. meretrix individuals randomly collected in 2019, the biology and anatomy, including the shell, morphometric relationships, shell polymorphism, shell form, internal anatomy and predation, are described. Meretrix cf. meretrix is a shallow burrowing species that has a uniformly smooth and highly colour morphic shell. The phenotypic traits of this species have different shell colours and pattern in addition to shell morphologies. Hitherto, the species has been harvested by locals as a food resource. Of late, however, the beach has been the target of local Hong Kong and other tourists who have over-exploited the M. cf. meretrix such that its population is now close to extirpation. Our observation supports that M. cf. meretrix is an ecologically important species in Hong Kong and the coast of the South China Sea. It is, therefore, proposed that Tong Fuk Miu Wan and Shui Hau Wan should be designated as a marine park to ensure the survival of this locally threatened species in Hong Kong.