The freshwater fishing seems to be very heavily regulated. They have closed areas to fishing and you have to have a permit to fish in freshwater, but not salt water. Lake Wilson is full of peaks and other fish that south Florida doesn't have, like little tetras. Collection of fish is heavily regulated. Even the university of hawaii has to go through strenuous permitting process to collect freshwater fish, because of the state's struggle to maintain endemic species. It is also really hard to find any infromation about freshwater fishing.
I went there this past week, and brought a rod with me. I fished waikiki and caught some ladyfish and jacks. The locals were all pretty nice about spreading local knowledge of saltwater fishing, and even keyed me into a spot where you could feed huge bonefish bread. Unfortunately very few knew about freshwater fishing, and I talked to fishermen from the north, south, and windward shores. They all call peaks tucanare, the Brazilian name for them, and they knew they exist, but they didn't seem to care about actually going to collect or catch them. Even after I told them they tasted good haha. They said salt water fishing was easier too. I didn't actually go to Lake Wilson, but I bet the locals around there could help you find about collecting exotics etc...