The net-cage farming area in Kuandian, the first county to embrace freshwater net cage farming in Liaoning province, has an annual output of 35,000 tons. More than 80 percent of its output is sold to the Republic of Korea (ROK) and Japanese markets where rigorous drug residue detection is imposed on aquatic products.

Fish species farmed in the 420,000 square meter area include carp, crucian, silver carp, bighead carp, blunt snout bream, grass crap, mandarin fish and sturgeon.

Net-cage farming pollution sources include fish feces, excessive fish food, domestic waste and other pollutants. These substances pollute the water, which cause diseases among the fish population. As a consequence, fish farmers have had to increase the anti-disease drug dose, which in turn has led to a vicious circle.

During the 11th Five-Year Plan period, the Kuandian municipal government implemented two types of eco-friendly fish farming practices.

One is to put the smaller net cages inside the larger ones. Fish feeding on baits are kept in small cages while filter feeding fish such as silver carps and bighead carps are bred in larger cages.

The second practice involves putting various species of fish in the same cage. Fish such as different species of carps, blunt snout breams and mandarin fish are bred together, each living at different levels in the water, thus making full and rational use of the water space.

Meanwhile, residues and feces of carps and crucian carps can be utilized by grass carps and blunt snout breams; diseased fish and weak fish become prey for more ferocious, carnivorous fish; thus lowering the break out of fish diseases and increasing the utilization rate of bait. In addition, filter-feeding fish also help purify the water.

Meanwhile, the Kuandian aquatic products department requires fish breeding companies to adopt pollution-free breeding practices, eliminating the use of illegal drugs to guarantee zero-residual-injury of net-cage fish from biological agents, herbs and other drugs.

At the end of last year, 28 fish species from 16 net-cage farming companies in Kuandian received health and safety certificates from the Ministry of Agriculture of the People’s Republic of China.

Edited by Chen Zhilin and Tania Lee