Welcome! Your pup can eat fish, but I don't recommend it as the main protein. Not all fish is the same as well … some, like tilapia, doesn't have much value at all. I give my boys sardines (that were frozen) because it's one of the ones that's high in a nutrient that I can't recall at the moment. I also limit their fish intake to once a week the most, just to get enough omega 6 to balance their diet.
I'm going to tag @RiiSii, as she's brought up her pups on raw. I think she started out with chicken as it's one of the softer bones.