南太平洋雌性大眼金枪鱼性腺成熟等级研究

Gonad maturity stage of female bigeye tuna (Thunnus obesus) in the southern Pacific Ocean

  • 摘要: 对2010年~2013年南太平洋海域采集的雌性大眼金枪鱼(Thunnus obesus)卵巢组织样本进行石蜡切片实验,研究其发育特征,鉴定其成熟等级并估算繁殖力。结果显示,卵巢的发育分为未成熟期、成熟前期、成熟后期、排卵期和排卵后期5个阶段;雌性性腺指数范围为0.26~8.58,平均为3.56,随叉长增长而增大;50%成熟叉长为116.32 cm;平均怀卵数为1.09×106粒;平均相对繁殖力为20.5粒· g-1。聚类分析显示,因钓获深度不同,2、3期为一类,1、4期为一类,5期独为一类。研究表明,在南太平洋海域,大眼金枪鱼初次性成熟年龄比其他海域提前,可能是受过度捕捞的影响。

     

    Abstract: We applied paraffin section method to investigate the reproductive features for female bigeye tuna (Thunnus obesus) in the southern Pacific Ocean (SPO), using ovarian tissues sampled at sea during 2010~2013. Maturity stage and fecundity were estimated under a microscope. The results show that the development of ovary was divided into five stages: 1 (immature), 2 (maturing α), 3 (maturing β), 4 (ovulating) and 5 (ovulated). Female gonad somatic index (GSI) ranged from 0.26 to 8.58 (average 3.56), increasing with the increase of fork length. Length at 50% maturity was 116.32 cm. Average batch fecundity was 1.09×106 pcs, and average relative fecundity was 20.5 pcs · g-1. Cluster analysis shows that there were three classes in terms of similarity in catch depth, i.e., Stages 2 and 3, Stages 1 and 4, and Stage 5. It is suggested that bigeye tuna reached first sexual maturity at earlier ages in SPO than in other areas, probably due to overfishing.

     

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