Seafood from the U.S.A. sent to China for processing and subsequent reexporting will not be subject to the retaliatory tariffs that the Asian country will be applying.
The fact is that the 25% tariffs announced by China for North American sea products have entered into force. Such tariffs arose in response to those set by the Trump administration.
This was announced by the National Oceanic and Atmospheric Administration of the U.S.A. (NOAA), to calm North American companies dependant on Chinese manpower to process, salmon, pollock and other products.