In Japan alone, there are three different types of fish sauce made: shottsuru (from Akita Prefecture), ishiru (from Ishikawa Prefecture) and ikanago-jōyu (from Kagawa Prefecture.) All are made from fish and shellfish.
Japanese versions of fish sauces are milder than those in other countries because Japanese consumers don’t like the strong fish smell of many imported brands.
Fish sauce has been far less popular in Japan than soy sauce. Its popularity only started to increase in the 1990s owing to increased familiarity with dishes from elsewhere in Asia.
Substitutes
2 tablespoons fermented black beans
4 tablespoons soy sauce
1 tablespoon miso
1 teaspoon sherry
Rinse excess salt off beans, if desired. Mash them in a bowl. Add soy sauce and sherry, stir all to combine, let stand for 10 minutes.
Strain, keeping liquid to use as a fish sauce substitute, and discarding the rest.