We feed our German Shepherd a raw diet. I saved the heads from an albacore charter trip to use for dog food. He doesn't like them and won't eat them. I'll be using them for feeding some
trees I think.
With regard to freezing, I think for salmon the recommendation is 1 week at 0F (-18C) core temperature is all that's required. I doubt minnows or shiners would need longer. Note that depending on the size/shape of the block of fish you freeze it can take as little has several hours or up to several days for the core temp to get that low.
So, if your dog will eat the fish, it's a great option. But it shouldn't be the primary food source. The pup will need a varied source of food including
chicken and beef, with the right ratio of bones and organ meats.