The Japanese fish commonly referred to in crossword puzzles are KOI (3 letters), TAI (3 letters), Fugu (4 letters), and Ayu (3 letters). KOI is a type of carp that is often kept in outdoor ponds or water gardens. TAI is a type of sea bream that is popularly served as sashimi. Fugu is a type of pufferfish that is considered a delicacy in Japan, but can be dangerous if not prepared correctly. Ayu is a type of sweetfish that is found in rivers and streams throughout Japan.