This file photo taken on Nov 24, 2022 shows a Pinctada maxima shell and pearls at the scientific research trial breeding project in Changjiang Li autonomous county, South China's Hainan province.

HAIKOU — In the waters of a southern Chinese island, scores of palm-sized pearl oysters hang tidily on the breeding cages. These oysters, scientifically known as Pinctada maxima, are primarily found ...