I'd very much like to see the item level for fish shown on their tooltip. It would make CUL desynth so much easier.

The Fish Guide already lists its level, category (lakes/sea/sand, etc), and prime locations. (Weather and time of day don't have a special place to be listed, but I'm not sure whether they're mentioned in the description. If not, they should be.) What would be nice, though, is a search function for it. I'd like to be able to right-click a fish, select search, and be taken to that fish's description in the Fish Guide if I've unlocked that info.