Samples used in the work were collected during April 1987-March 1988 in Honghu Lake. 729 specimens were studied for age structure and growth of the catfish, 1095 for the feeding, and 340 for the spawning of female. The age determinated from Neural Complex shows that age composition of the male is made up of 5 age groups, and the female of 4. Individuals of 1 and 2 age groups in male and female are 71.3%, 77.6% respectively. Growth rate of male is different from the female's, the VBGF for the former could be written as: Lt = 287 |1 - exp(-0.1581 (t + 1.19))| where Lt in mm, t in age-year. Length-weight relationship is described by the function: W = 4.9271 * 10~(-2)L~(2.5731) where W in gram, L in cm. Fitnees degree of the determinated age distribution to the length group distribution of catch in female is more than that in male, it is that length variance probably relates to the fitnees degree. Food habit changes with life stages. The catfish of 10-30 mm have Cladocera and Chironomids for their main foods, those of 30-80 mm are keen on shrimps and small fish, water insects are greater part of the catfish diet which body length are over 80 mm. Spawning stage is from the middle period of May to the first period of August. Reproduction occures in 2 batches. Age of mature is 1 year. Relationship of fecundity and age is shown in a linear line: F = 576.7 t + 903.5 where F is number of eggs, t is age. Relationship between fecundity and body length presents: F = 4.56 * 10~(-3)L~~(2.78) where F is number of eggs, L in mm. Spawning stock, which sex ratio (female:male) is 0.87:1, is composed of remainder stock and recruitment stock, and the latter is approximately half of the former. The recruitment stock is constructed by individuals of 1 age and part of 2, the remainder stock includes individuals of great many with 2 age and all other ages. The concept of fish diminution is a phenomenon that product of any age group in one year is less than that of corresponding age group in optimum growth year. In the concept, the product is result of weight multiplied by length. Features of fish population with diminution are expressed in three aspects: 1. young individuals take an absolute dominant position. 2. size of individuals developing to mature becomes small. 3. population abundance increases. Causes leading to the fish diminution may be: 1) free degree of spatial niche; 2) water temperature, 3) fishing intensity, 4) structure of fish community, 5) probability of catching food.