Trout, flounder and redfish are all superb!!! If there is one bit of advice for these is don't over cook!!
Flounder stuffed with crab meat and baked is a meal to die for.
Fried trout fillets are a real delight. if he's very big cut fillets into pieces and use your best batter, mine always has corn meal in it.
Redfish are often cooked "on the half shell". Fillet leaving the tough scaled skin on. Oil the scaled side real well as it will act at the pan. Put your "Poison" on the flesh side. We love lots of simple butter with spiced salt, many love Ranch dressing, but there's lots of choices. This is put on the grill scales down. Do not over cook, just till the meat flakes. If careful with a spatula you can lift the meat off the scaled shell.
All is best eaten with either a southern beer; Shiner, Pearl, Abita or south of the border beer; Corona, Carta Blanca, Pacifico Claro (my favorite). Chips n salsa with some guacamole are great for appetizers to get the beer and fish stories going.
Hey if you don't catch any there's a bunch of awesome seafood places on the Island starting with Giados.
It's all good.
Pete A.