Every time you feed something to an animal, that animal uses some of the nutrient value to maintain itself. This goes for BSF too. Their best use is for things that the chickens won't eat themselves. So the ideal in my mind would be to feed the fresh fish scrap to any critters that might eat it....poultry, pets, other fish, etc. Any that is too spoiled to do this with (and chickens, especially, will eat some pretty vile stuff!) would then go to the BSF for conversion....along with some, at least of the manure from the poultry, pets, and people! The BSF do serve to spread out the feed yield since they can store dormant for quite a while, but you might be able to sun-dry the fresh scrap and store that with the same idea in mind. Recycle at the highest level is the operative principle here. Composting or soil application is the final, last use of an organic resource, after any other yields have been taken.