Iwashi(sardines) is popular fish in Japan. and people like to simmer this kind of fishes as a nimono. I simmered them with water, sake, mirin, and umeboshi. and added a teaspoon of soy-sauce, because, umeboshi has enough saltiness. It goes together with rice. They are small and the bone are weak, so that you can eat whole. Of course, You should clean the inside and chopped the head. I think it can be nice as a marinated dish.