In fresh water lakes and streams use the same gear and lures that you use for largemouth and smallmouth bass - here you will catch guapote and guapatillo. Popping bugs on a flyrod like you use for bream, bluegill, pumpkinseeds and the like will drive the mojarra wild too. They are like bluegills on steroids and are really fun. Another fish that takes surface lures or flies is the machaca or sabalito, little tarpon. It looks like a small tarpon, leaps like all tarpon but be careful it has teeth like a pirana which is uses to eat fruit and nuts as they fall into the water. Lake Arenal and the rivers feeding it are on the tourist trail, bring your gear.
Surf casting with lead head jigs and mirror lures as is done on both coasts of the US for stripers or rockfish will work in tropical waters, but will result in snook and snappers. Just get beyond the first wave into the trough. I like the river mouths and am partial to the Parrita area.
Trout are trout, especially the rainbow trout; they came from the McCloud River in Northern California and behave here just as they do in Oregon and New Jersey. They are smaller, so stick to small lures and flies. Rivers holding trout include the Savegre, the Toro Amarillo, and most of the headwaters of the famous rafting rivers.
Tarpon are different, maybe not for Floridians, but for me. I have yet to catch one. There are famous lodges in the Northeast of Costa Rica at the Rio San Juan and Rio Parismina, and tarpon can be found in the Southeast too. Juar Google Jim DiBerardinis, he's the Wheeling College guy who found them there and has developed a fishing service.
