Customs authorities in China say the value of seafood imports from Japan plunged by about 30 percent last month from a year earlier.
A report released on Friday shows China's imports of Japanese marine products totaled about 32 million dollars in July.
Chinese authorities have increased radiation screenings of Japanese seafood in light of Tokyo's plan to release treated and diluted water from the crippled Fukushima Daiichi nuclear power plant into the ocean.
But the products are now being held up at Chinese customs for longer, which negatively impacts freshness. Some Japanese restaurant operators in China are now using domestic products instead.
Japan's agriculture and fisheries ministry says seafood exports to China in 2022 totaled about 600 million dollars. That's more than the figure for any other country.
Japanese officials are finalizing the schedule to release the water from the nuclear plant. Observers fear the Chinese government could take further action.