Fishing is designed to be more of a game of hide and seek with the player base sharing information on where to find the fish and what bait to use (beyond the hints given by the dialogue).

For later expansions, there's usually only the initial freshwater and initial ocean bait (or spearfishing) that's needed to catch the required fish so that cuts down on having to keep track of a large number of possible baits.

When you're still not certain what to do, there are multiple fansite databases to use as reference. While more hardcore fishers have their favorite websites for very detailed information, I'll generally use Garland Tools and enter the fish name into their item database. It will list the name of the fishing hole and what bait/spear gig to use in the item information, which is generally more than enough to finish the quest.

Fishing is very much a "you love it or you hate it" activity in the game. Because it has little practical use for crafting, you don't really miss out on anything if you decide to skip it completely or take a more minimalist approach like I do (quickly leveling it so I'll be able to catch whatever fish I need for CUL then ignoring it).