长江口凤鲚产卵群体繁殖力特征

Fecundity characteristics of spawning stocks of Coilia mystus in Yangtze Estuary

根据2018年5—7月以及2019年5月和8月在长江口水域采集的凤鲚(Coilia mystus)样本,对其生物学指标进行相关研究,结果表明:雌性凤鲚的肥满度(K)均值为0.32,雄性为0.37;雌性凤鲚性腺指数(gonadosomatic index,GSI)均值为18.58%,雄性为7.47%。2018和2019年长江口凤鲚的卵径分别为0.68和0.70 mm,与以往研究相比凤鲚的卵径有变小的趋势。2018和2019年的个体绝对繁殖力分别为11621和6131粒,产卵群体的年龄结构组成是繁殖力年间差异的主要原因。凤鲚的绝对繁殖力(F)和体长相对繁殖力(F_(L))与体长、体质量、净体质量和性腺质量呈正相关,体质量相对繁殖力(F_(W))与性腺质量和性腺指数显著相关。经逐步回归,绝对繁殖力与生物学指标的关系为F=5059.50W_(1)+1009.00(R^(2)=0.73);体长相对繁殖力与生物学指标的关系为F_(L)=22.77W_(1)+27.71(R^(2)=0.76);体质量相对繁殖力与生物学指标的关系为F_(W)=2614.35I_(GSI)-40.67W_(1)+412.41(R^(2)=0.60),个体繁殖力与性腺质量的关系最为密切。用核移位法得到长江口凤鲚2018和2019年的产卵分数分别为0.26和0.24,采样时间不同可能导致了产卵分数的年间差异。本研究分析了长江口凤鲚的繁殖力和产卵分数,可为采用日产卵量方法估算长江口凤鲚产卵群体生物量提供关键参数,以期为长江口凤鲚资源恢复效果的评价提供依据。

The biological indices of Coilia mystus were studied based on samples collected from May to July 2018 and May and August 2019 in the Yangtze Estuary.The results showed that the average condition factor(K)of female C.mystus was 0.32%,and that of male C.mystus was 0.37%.The average gonadosomatic index(GSI)of female was 18.58%,and that of male was 7.47%.In 2018 and 2019,the egg diameter of C.mystus in the Yangtze Estuary was 0.68 mm and 0.70 mm,respectively.Compared with previous studies,the egg diameter of C.mystus tended to be smaller.The average absolute fecundity of C.mystus in 2018 and 2019 were 11621 and 6131,respectively.The difference in absolute fecundity between 2018 and 2019 may be caused by the fecundity difference between different generations.The absolute fecundity and body length relative fecundity of C.mystus were positively correlated with body length,body mass,net body mass and gonad mass,and the body mass relative fecundity(F_(W))was significantly correlated with gonad mass and gonadosomatic index.Individual fecundity is most closely related to gonadosomatic index.Stepwise regression showed that the relationship between absolute fertility and biological indices was as follows:F=5059.50W_(1)+1009.00(R^(2)=0.73);F_(L)=22.77W_(1)+27.71(R^(2)=0.76);F_(W)=2614.35I_(GSI)-40.67W_(1)+412.41(R^(2)=0.60).The spawning fraction of C.mystus in 2018 and 2019 were 0.26 and 0.24 by migratory nucleus method.The difference in sampling time may have caused the annual difference in spawning fraction.The study on the individual fecundity and the spawning fraction of C.mystus in the Yangtze Estuary could provide a key parameter for assessing the spawning stocks biomass of C.mystus in the Yangtze estuary by using the daily egg production method.It provides some reference for the evaluation of restoration effect of C.mystus resources in the Yangtze Estuary in the future.