Ever since Taiping Island was "downgraded" to a rock, Taiwan administration has focused on what the situation of future fisheries will be, but intentionally evade the issue of the sovereignty ROC over South China Sea, which is the fundamental ground for all rights, including that of fishing. 

But how can Cai and DPP safeguard our fishermen in that vast area?  By naval force?  Basically, Taiwan could take care of Vietnam and the Philippines in that regard; however, Uncle Sam, or the Dad, won't let Taiwan do that.  Then those fishermen's only and last recourse is to seek protection from China's Mainland.  Like I've always said: hoist a China national flag, and don't forget to apply and install a Beidou in your boats.  Still want to be Cai and DPP's constituents?  Suit yourself then.  That's the only "right" you could exert, at home.