hhmm.. what do i do with this fish?

[Niwashi]

1. how do i know which fish can be use as bait? cant figure out how to know that a fish that i catch can be bait (meaning before turning it into a bait by recipes)

I'd like to know the answer to this one, too.

2. There are fish that have differrent "grade" e.g. http://ffxiv.gamerescape.com/wiki/Crayfish.. but i dont get why would someone would like a higher grade; it seems that u need more perception (especially to make it HQ quality) and the recipes dont seem to distigue between both of them (based in akchemist and culinary recpies up to lvl 30)

The recipes that use an item can use either the normal or high quality version of that item, but using the HQ ingredient gives a boost to the quality rating on the synthesis, so you have a better chance on getting a HQ result. (You have to select the number of HQ ingredients you want to use in the crafting window. By default, it will use the normal quality ones.) Oh, and you can also get more XP for the synthesis based on the quality rating, regardless of whether you end up with a HQ result.