Knife-fish dumplings offered at restaurants draw crowds of foodies. [Photo provided to China Daily]

Sky-high prices

At fish markets in both Shanghai and Nanjing, the capital city of Jiangsu province, knife fish weighing above 100 grams are rare and carefully guarded. In fact, there is a strict "supply-to-order" routine adopted by most dealers: they only stock the fish when there is a confirmed buyer.

Knife fish weighing less than 100 grams each sell for an average of 4,000 yuan per kilogram, while bigger ones cost as much as 12,000 yuan per kg. The prices are double last year's and higher than at any time since 2013, when the anti-corruption ban curbed luxury spending.

Chen, however, believes the charm of the knife fish has nothing to do with its price. Ever since his childhood, when the fish was sold for less than 50 yuan per kg, he found its flesh as well as broth "irresistibly xian". The common character means savory in Chinese, but Chen uses another tone to give xian the meaning of fairy or divine.

"When a table of diners is served ... and everyone takes a bite, the table suddenly becomes quiet. Although people are just busy with picking out the bones, I think it's a kind of silence-is-golden tribute to the fish," says Chen.

Zhou Zhuocheng, a committee member of the China Fisheries Association, categorizes knife fish into three types－lake, river and ocean. Although the three are essentially the same species, river-caught fish, especially from the Yangtze River, are deemed particularly precious. Those caught from March to early April are the crème de la crème, when the creatures have just traveled from the ocean to the river to lay eggs. The variation in water pressure is believed to change the density of the fish bones, making them as soft as hair and sometimes edible.

Unfortunately, the unique character of the fish has invited massive and unsustainable fishing.

According to statistics from the Freshwater Fisheries Research Center of Chinese Academy of Fishery Sciences, the production of knife fish from the Yangtze River peaked in 1973 at 3,750 tons. By 2002, the harvest has fallen below 100 tons, and in 2011, the latest data available, it was 12 tons.