Ayu is a type of freshwater fish commonly found in rivers and lakes in East Asia, particularly in Japan and China. Known scientifically as Plecoglossus altivelis, it is recognized for its elongated body and silvery color. Ayu is often associated with seasonal fishing and is a popular delicacy, especially during the summer months. The fish is notable for its unique life cycle, migrating from freshwater to the ocean and back. Ayu is also celebrated in Japanese culture, where it is featured in various dishes, such as grilled or served in soups, highlighting its importance in local cuisine.