Not sure where the coastal hotspots are for trophy fish? Don't own a boat? No worries! Taiwan supports one of the region's biggest aquaculture industries and many local fish farms will let you wet a line for a nominal fee--and you can keep and eat your catch guilt-free if you like.
I came across the video below on YouTube of a gent nailing a nice grouper and barramundi at a commercial pond. Where it is on the island I don't know, but I would love to find out if anyone does know.