if you are using absolutely fresh fish then your problem wouldnt be from bacteria on the inside of the meat but from parasites if the fish have them. that said, i dont know if all parasites are always very obvious, but if you feel safe about the meat you are using, i would still soak it in vinegar or lime juice before hand to "cook" the very outside, just to kill the surface bacteria while still keeping the fresh taste of the fish. i have heard of reports in my state of bluegills having wormy parasites, im not sure if it was in the meat or on the skin, and i have also heard of wormy parasites on the outside of trout. but freshwater allows for a lot more stuff to grow and unseen stuff could be in the meat. if it was me i would also steam or smoke it first.