Potion Permit

At first you need to get the Basic Fishing Rod. To get this, you have to:

1st: Clear the Quest "Clearing the Landslide" and
2nd: Visit the Primrose Sail, Leano will give the Basic fishing Rod to you
3rd: Buy plenty of Worms, 10g each.

The only fishing spot you get fish is the one at the Park in Moonbury. Here you can get the following fish:

-Anchovy
-Crayfish
-Eel,
-Mackarel
-Sardine
-Shrimp
-Small Chest (Dont know, if it counts)

Now you need to get the Intermediate fishing Rod. To get this, you have to:

1st: Fish alot at the Park fishing spot (around 50 times)
2nd: Friendship Leano to lvl 2
3rd: Leano will appear at the Bulletin board to visit her at the Park - a cutscene will trigger
4th: Gather Material; 5x rainbow dew, 5x silver nugget, 10x rigid pelt and bring it to Leano

She will now give you the upgraded rod. With this, you can access the River fishing Spot in Noth-East of Moonbury (you need to clear it from the slime first)

Here you can get the following fish:

-Blue Marlin
-Catfish
-Goldfish
-Squid
-Seabass
-Sturgeon
-Small Chest (Dont know, if it counts)
-Large Chest (Dont know, if it counts)

Now you have access to 12 kind of fish. Good luck!