温台渔场日本鲭的繁殖生物学特征

The reproductive biology of chub mackerel(Scomber japonicus) in Wen-Tai fishing ground

利用2012年春季在温台渔场对日本鲭（Scomber japonicus）繁殖群体连续6批取样的生物学测定数据,对其繁殖生物学特征进行了研究。结果表明,叉长340 mm以下群体中,雌雄比基本符合1∶1的性比关系；叉长340 mm以上群体中,雌鱼显著多于雄鱼（P〈0.05）。GSI随时间的变化结果显示,温台渔场日本鲭的主要繁殖期为3月中旬至4月中旬；不同时间段的雌鱼和雄鱼GSI均总体表现为雌鱼大于雄鱼（P〈0.05）。不同性腺发育阶段的平均摄食强度总体表现为雄鱼大于雌鱼。不同性腺发育阶段的雌性和雄性的肝指数均雌性显著大于雄性（P〈0.05）。绝对繁殖力范围为44017~734684粒/尾,平均值为（173867±15719）粒/尾,优势组为（10~30）×10^4粒/尾,占70.37%；相对繁殖力范围为187~1403粒/g,平均值为（538±31）粒/g,优势组为（390~700）粒/g,占66.67%。卵径范围为0.27~1.22 mm,平均值为（0.86±0.01） mm,优势组为0.7~1.1 mm。温台渔场日本鲭的绝对繁殖力低于黄海北部而高于台湾海峡,相对繁殖力高于历史水平,平均卵径小于20世纪80年代,雌雄鱼的最小性成熟叉长均有一定程度的降低。以上结果都说明日本鲭为应对高强度捕捞和环境胁迫压力而采取增加相对繁殖力、减小卵径、提早性成熟等繁殖策略来维持种群数量和保证种群的延续。

The reproductive biology of Scomber japonicus was investigated by six consecutive samplings of reproduc-tive stocks of this fish （spring, 2012） in the Wen-Tai fishing ground （27＆#176;00′–28＆#176;00′N, westward from 125＆#176;00′E to the steam boat fishing prohibition zone）. The results showed that females to males conformed to a ratio of 1∶1 in the fork length 〈 340 mm group, but female fish out-numbered male fish significantly in the fork length 〉 340 mm group. Variations in the gonadosomatic index （GSI） over time showed that the main breeding season lasted from mid-March to mid-April in this location. Female and male GSI values showed significant differences in the time periods, and the overall performance for females was higher than in males. We found the average feeding intensity to be greater in males than in females in the different gonadal stages. The liver index showed significant differences in the different female and male gonadal stages, with values for females higher than males. Absolute fecundity was 44 017–734 684 grains （mean ±SD, 173 867 ± 15 719 grains）, while the dominant group was 10–30×10^4 grains （70.37%）. Relative fe-cundity was 187–1403 grains/g （mean ± SD, 538 ± 31 grains/g）, and the dominant group was 390–700 grains/g （66.67%）. Egg size was 0.27–1.22 mm （mean ± SD, 0.86 ± 0.01 mm）, while the dominant group ranged from 0.7 to 1.1 mm. The absolute fecundity of S. japonicus in the Wen-Tai fishing ground was found to be less than that of the northern Yellow Sea and higher than that of the Taiwan Strait. Relative fecundity was higher than historic levels, but the mean egg size was found to be lower than in the 1980s, and the minimum fork length of males and females at maturity ex-perienced a certain degree of reduction. This suggests that reproductive interventions （i.e., increasing relative fecundity, reducing egg sizes, and promoting early sexual maturity in the fish） are needed to cope with the high fishing intensity and environment stresses that had threaten Scomber japonicus reproductive stocks.