It depends if the peanut butter has xylitol in it. Xylitol is lethal to dogs.
Peanut butter also contains lots of fat and salt. Use a xylitol-free one only as a treat.
Short-lived fish like salmon, cod and whitefish are fine. However, longer-lived fish such as tuna can contain a lot of mercury. A bit now and then is okay, but not all the time.
Fish bones should be avoided, as they’re brittle and sharp. They could result in needing surgery for your dog.
Overall, though, feeding peanut butter with xylitol to your dog is probably worse. It takes 22 times more dark chocolate to kill a dog than xylitol.