Damselfish

This is a Space catch, which means fishing from the very top of the map. Natural lakes that high up are rare, so the usual approach is a skybridge with a small pool poured out of buckets. Keep the spot clear of Corruption, Crimson and Hallow, since a tainted pool hands you that biome catch list instead.

The reason to keep a few is Calming Potion, which thins out enemy spawns while you are mining or laying out a build. It also goes into Seafood Dinner if you would rather have the food buff. Neither is worth a dedicated trip, so fish for these while you are already up there chasing the other sky catches.