Our family will be attending a wedding in Connemara. As a family we want to visit Belfast squeeze in some fishing and then make our way to Connemara for the wedding. We can reverse the trip either way. What guidelines can you offer?
Your other post indicates that you plan to fly into Shannon for a stop in Clifden. If that's still the case then driving to Belfast after your stopover in Connemarra would make the most sense logistically.
Doing the trip as an open jaw (fly into Shannon, fly out of Belfast or Dublin) would be more efficient than having to backtrack and fly out Shannon but know that there's usually a punishing one-way drop charge if you rent a car in the Republic and then drop it off in NI. If you picked up the vehicle at Shannon, drove thru NI, and then dropped the car at Dublin airport the drop fee is minimal.
Can't help you with the fishing, but you can google "fishing Northern Ireland" to see a multitude of resources that can answer your questions.
Safe travels.