wkl2020,
unfortunately thers is not much fishing available in Dongguan. If you have free weekends try to get to Autou (about one and a half hour car ride away) which is on the south eastern coast. It is a fishing village and you can get a fisherman to take you out.
Theres a new highway opened recently so it will be quicker to get there.
all the best
Carry a rod and speak softly.