Three types of saltwater fish reared in Pearl River Delta farms have been found to contain cancer-causing organochlorine pesticides such as DDT.
Mainland scientists heading a study advised the public not to eat orbfish , red drum and mulloway from the region.
Hong Kong Chamber of Seafood Merchants chairman Lee Choi-wah confirmed that these species were on sale in Hong Kong and that some stocks were imported from fish farms in the Pearl River Delta.
Zeng Yongping, director of the Chinese Academy of Sciences' State Key Laboratory of Organic Geochemistry, who headed the study, said even if consumers ate orbfish just once a month, the likelihood of getting cancer was more than one in 10,000, or 100 times higher than the maximum set by the World Health Organisation.
'My advice is that consumers stop eating fish, especially the three named species produced by Pearl River Delta sea farms, until we can single out the exact sources of the pollution,' Professor Zeng said.
The scientists also found poisonous pollutants spread much faster through the fish than previously thought. It was believed that most harmful materials were concentrated in internal organs such as the liver, but the latest study shows the contaminants were evenly distributed throughout the body.
'Fish muscles seem to be able to absorb more pollutants than we previously thought. Some people believed that it was safe to eat just the meat, but this does not hold up,' Professor Zeng said.