THE RATIONAL DESIGN OF POND FISH CULTURE WITH REFERENCE TO THE PRINCIPLES OF YIELD INCREASE——Ⅰ.The biological charateristics of the winter fingerling in pond

This paper presents results from a series of pond and indoor experiments conducted during 1986—1989. (1) Grass carp fingerlings continue feeding during most of the winter—time in the area south to the Changjiang River. The mean growth rate of fingerlings was 10—14% during winter when the fish were not crowded and fed properly. There were no significant differences (p0.05) in the condition factor, number of red blood cells, homoglobin, total plasma protein, and chemical composition of muscle and liver before and after winter. (2)In the fingerlings in partially crowded wintering ponds, body weight and condition factor did not change obviously (p0.05) over winter, but the number of red blood cells, total plasma protein, and lipid content in muscle and liver decreased significantly (p≤0.05), even when they were fed. (3)When in fingerling density stocked in ordinary wintering ponds only and rarely fed, the mean weight loss was 9—14% over winter. Their mesenteric fat was almost depleted. The condition factor and protein and lipid contents of muscle and liver decreased greatly (p≤0.05). The fish were unhealthy and suffered from severe anaemia. The experiments demonstrated that different methods of winter not only determened the fingerling's quality, but also affected the production of adult fish in the following year. It is necessary and feasible to abolish the method of concentrating fingerlings for winter, in which is adopted in most regions especially around the middle and lower reachs of the Changjiang River, and in some areas around Huaihe River and Huanghe River.