What started off as me jealously trying to fish out an Anglerfish with basic bait after my friend nabbed a massive one that fell into our boat led to me spending hours fishing for every fish in the game.
After I went down the rabbit hole trying to figure out why my bait wasn't working and read about the progressive bait system through each biome, I was instantly hooked. It's very satisfying to jump from biome to biome catching fish to use as bait in the next one. I've now caught every fish in the game aside from the Tetra and the Coral Cod. (I did pick up a Coral Cod in the Deep North after it washed ashore, but I don't really count that since I didn't actually fish it out).
Obviously the fishing system is incomplete, what with every fish except for one giving just regular raw fish, but as an optional trophy challenge it's very fun. Highly recommend you give it a try if you're a collector.
Thanks devs!
Source: https://www.reddit.com/r/valheim/comments/zxot0d/this_fishing_update_is_great/