An article from this fall, from a professor in Singapore (i.e. not knee-jerk pro-Chinese government), states that China has been implementing a number of policies to change its fishing industry. Pretty interesting stuff if you care about the world's overfishing problem:

https://www.eastasiaforum.org/2022/08/03/chinas-efforts-to-reel-in-overfishing/

The territorial waters discussion is a bit of a red herring (haha), but if countries were to put limits on fishing imports it would certainly have an effect. Three quarters of US seafood is imported, and its biggest import source is China.

https://www.fishwatch.gov/sustainable-seafood/the-global-picture