Sorry I didn't respond right away. I actually wrote up a response to your post on Friday, was logged off by the time I tried to post it and by then it was time to leave the office.
That sounds like a fair price for one of the boats out of Zhunan. I haven't been out of that port before, but my fishing buddies in Hsinchu say those boats usually fish the wrecks and reefs in the area for small grouper and snapper. Let us know how it goes. My family responsibilities have severely cut into my fishing time these days.
Speaking of river fishing, here are some good spots for tarpon in Wugu
that another fishing buddy recently tipped me off to. Tarpon are in the area through the end of December. Best times are a couple of hours before and after high tide.