1. Preheat broiler ten minutes.
2. Split the mackerel, dust with flour, place skin side down in a greased baking pan and dot heavily with butter. Sprinkle with salt, pepper and paprika.
3. Broil the fish two to three inches from the source of the heat in a preheated broiler, basting occasionally. Cook until the fish flakes easily when tested with a fork, six to ten minutes.