http://en.ff14angler.com/
Mostly use this one, weather cycles, fish locations, when its catchable during those times etc..

http://forum.square-enix.com/ffxiv/threads/181498-Desynthesis-Endgame-Guide
And this one sometimes too, not really about fishing, but atleast it list the ones that give mats/gear when desynth AND list what gathering is needed..Lucendi Sundwilfwyn

Provided by Eli :)

Annother useful resource for ARR fish:

http://ffxivfisher.appspot.com/?

Hopefully they will eventually add the heavensward timed / weather fish to the list.