Meadows fish you can either find on the shore or use the fishing rod from Haldor. Black Forest fish (Trollfish) require regular bait & a Troll Trophy/Head. (cook bait in cauldron)

Swamp Fish (Giant Herring) need regular bait & a Abomination Trophy (cook in cauldron) They seem a bit more dormant than other fish for some reason though, they will eventually bite the bait.

Mountain fish you need to find Frost Caves to find Tetras, but you need to know what cave to look for. I have a seed if you want that specific fish. Use the seed & world ''Arjak'' there is a Mountain North North west (slightly) north of spawn, after crossing a river & a small patch of both Meadows & Black Forest, over the river there is a large mountain on the north side of the mountain is where the specific cave is.

Also if you want to make the cold bait (again, cauldron) need 1 Fenring Trophy & bait.

https://steamcommunity.com/sharedfiles/filedetails/?id=2940335254

Cave pool is on the left side down a passageway that branches off to the right after breaking the ice entrance.