Updated at 1.34pm: The Agriculture, Fisheries and Conservation Department said on Tuesday it was tightening up registration rules at the Western Wholesale Food Market to help maintain the quality of freshwater fish there. A department spokesman said that from Tuesday all visitors and vehicles to the market would now have to register. The spokesman said these measures were necessary to strengthen control of the food market and to combat the landing and distribution of freshwater fish without health certificates. Fish without health certificates can pose a major threat to people?s health ? as recent food scares involving freshwater fish in Hong Kong have shown. The spokesman said more security staff had been deployed to enforce the registration rules at the Western Wholesale Food Market. The new measures were first implemented at the Cheung Sha Wan Wholesale Food Market on May 15. But the spokesman said on Tuesday there had not been any notable changes in the number of people and vehicles entering the market. Hong Kong experienced a major freshwater fish scare last year when imported fish were found to contain malachite green ? which can cause cancer. Since then, fish imported from the mainland have been required to be produced from accredited fish farms. In April, two fish-smuggling cases detected at the Cheung Sha Wan market showed that some smuggled fish still contained malachite green. The smugglers were also selling endangered species.