Over the past two decades, Zheng Jinliang has released more than 160 million fish into the Yangtze River in Jiangsu province at his own expense.

Now in his 60s, the former businessman has witnessed fish stocks of rare species dwindle over the past 50 years.

Zheng, who has lived in the riverside city of Jiangyin his entire life, said as a result delicacies such as the Chinese tapertail anchovy－known as daoyu, or knife fish by locals－have skyrocketed in price.

Degradation of the aquatic environment and overfishing caused by high demand have driven the price of the fish to more than 10,000 yuan ($1,500) a kilogram.

"I used to see fishermen carry baskets of fresh fish to sell when I was a little boy," Zheng said.

"The knife fish were sold for 0.6 yuan a kilogram. My mother often asked me to carry a basket of vegetables to exchange for the knife fish on fishing boats."