关键词: 长江下游, 刀鲚, 生物学特征, 最大持续产量

Abstract: Studies on biological characteristics ,change of catch per boat and maximal sustaining yield (MSY) of Coilia nasus schlegel in the lower reaches of the Yangtze River were carried out during the period from 1993 to 2002.The result showed that average bodylength and bodyweight were 29.19 cm and 94.33 g in fishing season. The correlative equation between bodylength and bodyweight could be expressed as Y= 0.004 8X2.906 9 and the coefficient of fullness was 0.379. The average value of absolute fecundity and relative fecundity were 23 695 eggs/fish and 229 eggs/g body weight respectively, and the diameter of matured egg was 0.77 mm. The correlative equation Y= 0.017 2X4.101 might be used between absolute fecundity and bodylength and it was Y= 305X-5 410.1 for absolute fecundity and bodyweight . Most of the fish were two years old in fishing season. The average value of the total catch per boat was 393.14 kg. Average annual catch was 891.51 t and MSY evaluated by model of Schaefer was 2 061.81 t in the lower reaches of the Yangtze River.Compared with historical data, the miniaturization of the fish was evident and the community age structure tended to be onefold and lowaged,at the same time ,the resource of C. nasus had decreased significantly.

Key words: lower reaches of the Yangtze River, Coilia nasus schlegel, biological characteristics, MSY