Washington (CNN) Matt Fass sells American-caught fish, but he's worried about President Donald Trump's threatened tariffs on China.

Why? China has become one of the leading fish processors over the past 20 years. That means that fish caught around the world are headed and gutted, frozen, and then shipped to China where it may be deboned or cut into a filet before coming back to the United States.

And that means that it's on the tariff list. Trump's tariffs would hit Chinese-processed pollock, salmon and cod -- even if it's originally an American catch -- unless the US Trade Representative's Office decides to exempt those fish from the list.

"We've been working with China for 20 to 30 years now. They have the expertise and the infrastructure," said Fass, president of Maritime Products International.

The Virginia-based fish company imports roughly 20% of the seafood it sells from China, depending on the time of year. Overall, a majority of the fish consumed by Americans is caught or processed overseas.

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