A scallopocalypse is laying waste to the popular delicacy in the Yellow Sea.

Giant Chinese seafood supplier Zhangzidao Group said yesterday it found more than 80 per cent of scallops at a farm in the sea between China and the Korean Peninsula had died due to "unidentified" causes.

The book value of the affected mollusks is 300 million yuan (S$58 million), the company said in a statement to the Shenzhen stock exchange. It is still assessing the damage, and the cause of death is unknown though believed to be natural, it said.

Zhangzidao's "ocean ranch" supplies 50,000 tonnes of scallops a year, according to its website.

Just over 100,000 tonnes of the bivalve were traded globally in 2018, according to the Food and Agriculture Organisation of the United Nations, with China accounting for one-third of both imports and exports.

The ecological environment in the North Yellow Sea is complicated and constantly changing, Zhangzidao said. Scallops accounted for 6 per cent of total revenue in the first nine months of this year, it said.

The Shenzhen-listed Zhangzidao Group, which calls itself an "undersea bank", has come under fire in the past for its declining scallop output. The average yield for the mollusks that started seeding in 2018 is expected to have dropped to about 3.5kg as a result of the deaths, down from 25.61kg per mu (about 675sqm) in the first 10 months of this year, the firm said.

Zhangzidao's shares tumbled by their daily trading limit of 10 per cent in Shenzhen yesterday.

BLOOMBERG