Ayu is named after its two balsam-filled cavities on its back, which emit an alluring fragrance. Ayu fish individuals are 10-30 centimeters long and weigh 50-100 grams, with a maximum weight of about 500 grams. Its sides are flat, greenish-yellow in color, with tiny scales and rich in nutrients. It is a delicious and nutritious delicacy that is both food and medicine. Ayu is not only a valuable small-scale commercial fish in my country, but also recognized as the most valuable freshwater commercial fish in the world. It enjoys the reputation of "King of Freshwater Fish" in today's international market.

Yongxi River produces sweetfish and has been recorded in the county annals. According to folklore, after Emperor Qianlong tasted sweet fish while traveling to the south of the Yangtze River, he was full of praise and ordered to include it as a tribute. Later, due to overfishing and changes in the ecological environment, it has become rare.