长江下游刀鲚生物学及最大持续产量研究

对1993~2002年长江下游刀鲚的生物学特征、单船产量变化及最大持续产量进行了研究。结果表明，汛期刀鲚平均体长为29.19 cm，平均体重为94.33 g；体长和体重呈幂函数相关，拟和方程为Y= 0.004 8X2.906 9，丰满度系数为0.379。绝对怀卵量平均为23 695粒，相对怀卵量平均为229粒/g体重，成熟卵卵径平均为0.77毫米；绝对怀卵量与体长的关系式为Y= 0.017 2X4.101，与体重的关系式为Y= 305X-5 410.1。汛期种群以2冬龄为主。研究期内刀鲚平均汛期单船总产为393.14 kg；长江下游刀鲚年均捕捞量为891.51 t，应用Schaefer模式估算最大持续产量为2 061.81 t。与历史资料相比，刀鲚个体小型化明显，种群结构简单化、低龄化，资源急剧下降。

STUDIES ON BIOLOGICAL CHARACTERISTICS AND CHANGE OF RESOURCE OF COILIA NASUS SCHLEGEL IN THE LOWER REACHES OF THE YANGTZE RIVER

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 bodylength and body-weight could be expressed as Y= 0.004 8X~2.906 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 equationY= 0.017 2X~4.101 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.