Co.Mayo would have to be the place for you to get fish on the Fly.
for trout we got Lough Conn(salmon also), Lough Cullin(salmon also), ,Lough Mask ,Lough Carra and Lough Corrib on its border

plus dozens off smaller lakes full off wild brown trout.
we got lough Beltra and Carramore, Furnace and Feeagh to fish for salmon and sea-trout from a drifting boat.
for salmon we got the famous river Moy, the Eirrif, spate rivers in Louisburgh,Newport river, Owenmore,Glenmoy,OwenDuff.
fish for trout in the rivers Robe,Gweestion, Pollagh and Glore plus Clydagh, Castlebar, and Manulla rivers.
plus Dozens off lakes to fly fish for pike.
a few hundred miles off coastline also to try and fly fish.
p.s. sorry if a forgot and loughs of rivers
Mayo is the flyfishing capital off Ireland .