中文摘要：

洄游性刀鲚是长江中下游重要的渔业资源,20世纪70年代以来,其资源量严重下降。研究以耳石为年龄鉴定材料,对长江口刀鲚渔获物的年龄结构和生长进行研究,主要目的在于确证刀鲚耳石上年轮,分析刀鲚渔获物的年龄结构和生长特征,评价刀鲚资源状况。2006年4月至2007年8月在长江口逐月采样,共采集了576尾洄游性刀鲚。对矢耳石横截面分析发现,从耳石核出发,腹侧生长轴具有周期性的直-弯生长模式,直线生长发生在4到12月,弯曲生长在10月到第二年的6月;边缘轮纹增长率分析也表明,这种直-弯生长模式具有年周期性,可以用来鉴定年龄。弯曲生长向下一个直线生长的转换发生在4月至6月间,将此转换定义为年轮标志。年龄分析表明,长江口刀鲚渔获物包括0龄至4龄共五个年龄组,以1龄和2龄个体为主,雌雄个体年龄组成相似,生长趋势也比较接近,拟合的von Bertalanffy生长方程为SL=327.69[1-e-0.51（t＋0.28）]（n=576,r2=0.71,P〈0.05）,标准体长和体重的关系为：BW=0.54×10-6SL3.36（n=576,r2=0.95,P〈0.05）。与20世纪70年代渔获物调查结果相比,现在长江口刀鲚种群明显低龄化和小型化,表明刀鲚资源已严重过度利用。降低刀鲚的捕捞强度是刀鲚资源保护和恢复的基础。

英文摘要：

Anadromous Coilia ectenes（Jordand et Seale） is a commercially important fishery resource in the middle and lower reaches of the Yangtze River.It usually feeds and overwinters in the Yangtze Estuary and the coastal waters Adults migrate up into the Yangtze River and its affiliated lakes in the spawning season.After spawning,they migrate down into the sea.Offsprings feed in freshwater and migrate down into the sea before overwintering.Resource of this fish has declined dramatically since late 1970s.The present research validated annuli in sagittal otolith and analyzed the age and growth of C.ectenes from the Yangtze Estuary to evaluate the resource condition of the population.A total of 576 individuals of C.ectenes were collected in the Yangtze Estuary monthly during April 2006 to August 2007.No periodic opaque/translucent zones were visible in the transverse plane of the sectioned sagittal otolith when examined with either transmitted or reflected light.Instead,periodic straight-curved zones,similar to those in sagittal otoliths of Coilia mystus[10],were observed along the ventral growth axes in the transverse plane under transmitted light.The growth axes from the core were generally straight initially,and then gradually curved to the distal side until a sudden break formed.After the break,the growth axes were straight,and the straight-curved zones were typically repeated,particularly in large individuals.In April,the margin of the growth axis was straight in some individuals,and the proportion increased in May and June.The margin of the growth axis was straight for all the individuals during July through September.In October,a small proportion of the sampled individuals displayed a curved growth axis,and this proportion increased in December.Marginal increment ratio analysis also showed an annual periodicity of the straight-curved growth increment.The shift from curved growth to the next straight growth occurred during April and June.We defined this shift as an annulus mark.The collected specimens were consis