Primitive survival fishing question - do I actually have to see the fish in the world, for it to be capturable via hooks/traps?

[Skala]

Or do the fish just "spawn" in the trap?

[Brady_The]

16 minutes ago, Skala said:

Or do the fish just "spawn" in the trap?

It's a spawn chance. You don't have to set up traps near physical fish entities in the world.