http://cimsec.org/evolution-of-the-fleet-a-closer-look-at-th...
Most Chinese fishing takes place right outside the EEZ in the high seas, and after the 2017 fiasco with a Chinese ship caught in the Galapagos EEZ they've been very careful not to actually enter its 200nm limit. The linked article has some great maps of AIS data that clearly show this. There may still be scattered instances of ships with AIS transponders turned off being sent into the EEZ or transfers from non-Chinese flagged vessels to Chinese ships, but according to the article "In most cases, what is detectable may not be illegal, and care is clearly being taken by the Chinese fleet to give the appearance of legal compliance with national and international laws."
The real bombshell is this here: "A task force report published in 2010 by Chinese government, industry, and academics argued that countries that have a longer history of using the ocean have more power in determining how resources are distributed and thus receive a larger share of those resources: occupying brings about rights and interests"
China is subsidizing a large deep water fleet so they become the largest fishers on the high seas outside of the 200nm EEZs and so can write the future rules for high seas fishing. As stated in the article, of the regional fishery management organizations that operate in the area very few Chinese ships are registered with the IATTC (founded 1949) despite China being a member. Rather, the ships are all registered with the SPRFMO (founded 2012). It's a lot easier to write organization rules when you're a founding member than when you join decades later. In international politics possession (in this case precedence) is 9/10ths of the law and you can be sure in any future negotiations over fishing quotas in the currently loosely regulated high seas China will have the largest voice because they have the largest fleet and largest historical catch.
While everyone's still back in the 80s guarding their 200nm UNCLOS EEZs China's already got the first mover advantage on everything outside those EEZs.