Fish raisers from Shandong Province who want to sell turbot in the city must first put down a security deposit with the Shanghai Fisheries Trade Association, according to a deal signed over the weekend.

The association signed the agreement with its Shandong counterpart, calling on fish farmers to put up a 30,000 yuan (US$3,750) deposit to ensure their turbot fish are safe to eat before they can be sold in Shanghai.

The agreement also said turbot fish raising companies should obey the country's laws on food quality and safety. No banned substance should be used on the fish during feeding or transport.

If the fish are found to contain a banned substance, such as the carcinogenic antibiotic AOZ, the companies will be forced to shoulder all of the responsibility, according to the agreement.

"Now the process of introducing turbot fish into the city's market is rather complicated," said Fan Shoulin, secretary general of the association. "The fish raisers should not only provide a local inspection certificate, but also should gain the recommendation of government authorities and both associations."

At present four brands of turbot from Shandong Province have been approved for sale in the city, including "Tianyuan" and "Penglaige." The recommended fish have a small paper card threaded into their tails, containing the name of the place of production.

The Tongchuan Road Aquatic Products Wholesale Market currently sells about 500 kilograms of turbot a day, about one-tenth of sales before AOZ was found in Turbot from Shandong late last year.

"The turbot sold in city markets is now safe to eat," said Tang Qiqing, director of the association. "We expect turbot consumption to resume to its normal volume around the Spring Festival."

Turbot raisers in Shandong said last week they plan to file a lawsuit against the Shanghai Food and Drug Administration over its inconsistent food safety criteria for fishery products.