Since my goal with fishing (besides leveling up and making money) is 'not dying while doing it', going to the higher level monster places to fish is a seriously poor idea, so I started looking around the cities.
Giant catfish (curse their name!) can be found in Sandy and cap at 31, so I'm going to remain in there for levels 27-31 (unless I get too annoyed with those damned fish). After 31 becomes the big, big problem... There's nothing around Sandy (in the safe and easy to get to areas, at least. East and upper west Ron) that's good for the post-31 range.
So I started looking at what the other cities have around them. Windy is as rich in fish as it is in distance between places within its city! Dark bass (33), orge eel (35), gold lobster (46), then mooke-onke (51)! (There are level 55, 69, 71, and 85 level fish there as well, but those are so far in the future there's no use thinking about them now.) Going from 35 to 46 is quite a bit of a jump, but should be do-able. And by using the right lure/bait, you can avoid catching the lower level fish (crayfish, sardines, moat caro, quus, pipira)!
To that end, I've worked up a spreadsheet of all the fish around Windy. Using the other charts, I made one single one with all the info: Which fish, where they are (some are only in the east or west outside of the city), level, and bait.
*Hopefully* I'll be able to chocobo before I hit 31 fishing, then getting back to Sandy to party up with LS folks will be totally easy. Hm. I suppose even if I can't ride the bird, if I just buy a teleport ride to the right crag then either we can meet there or I can run south and meet people. It won't be anywhere near as handy as being in Sandy, but a fisher's got to go where the fish are...
On a perhaps-related note: It's very strange, but people keep /tell'ing me for help. People who aren't even in the same area as me! Mostly it's fishing help, but a lot of times it's people lost or asking general game questions or where they might want to level up. I can only think of three reasons this might be:
1) I'm in Sandy a lot, like nearly all of my online time. They might see me so often that they think I'm an experienced player. (However, this doesn't explain why I was getting paged with questions in Windy, too.)
2) Because I have a name that's a real thing (Thistle, as opposed to Uhrj2ofgnuiwngfwg or something like that), maybe it's easier for people to remember my name when they need help.
3) It's just random, and there's no reason behind me being paged so much more than I used to.
I'm set /anon all the time now, so it can't be something like "Oh, a white mage likes to help people so I'll try asking one!".
I love helping people (especially when you can tell they're new and yet thy're still polite and friendly), I'm just curious about the reason behind them finding me. (There was a new player who paged me in Windy, and I just wanted to find him and hug him! He paged something like "Excuse me, might I ask a question? Can you tell me where the low level monsters are? I'm new and I don't want to take on something too strong." He sounded just like how I had been! Eee! :) So I explained to him how monsters got stronger as you moved from the city.)