中部大西洋剑鱼栖息深度分布特征

根据2007-2008年和2010-2011年我国金枪鱼延绳钓渔业科学观察员收集的钩位信息,运用悬链线理论,估算了大西洋中部剑鱼(Xiphias gladius)的钓获深度分布。剑鱼的钓获深度范围为124.6～280.5 m,平均深度215.2 m,标准差46.5 m。剑鱼的渔获比例随钓钩的深度增加而明显变化,在深度220～250 m时渔获比例最高,而后随深度增加而明显减少。在较浅深度,雄性剑鱼的比例较高,但随着钓钩深度的增加,雌性剑鱼的比例增加,随后趋于平稳。钓获的剑鱼平均长度(下颌尾叉长)随钓钩深度增加而增大,在较浅处(120～180 m),平均长度分布最小;在较深处(270～300 m),平均长度分布最大。渔获的性比和个体组成变化对资源数量变动具有重要影响,对掌握剑鱼的栖息生态和资源可持续利用研究具有参考价值。研究亮点:不同钩位的渔获率差异是延绳钓渔业中的重要研究课题,特别对于兼捕种类。对于大洋性剑鱼,这方面的信息还很缺乏。利用海上实测数据,分析大西洋剑鱼的深度分布及其性比和渔获长度差异,为研究栖息生态和降低兼捕提供重要依据。

Characteristics of the habitat depth for swordfish in the central Atlantic Ocean

Based on hook number information collected by scientific observers on the Chinese tuna longline vessels in the central Atlantic Ocean from 2007 to 2008 and from 2010 to 2011, the distribution of capture depth of swordfish (Xiphias gladius) was estimated by using catenary curve method. The depth range of the captured swordfish was from 124.6 to 280.5 m, with an average of 215.2 m and standard deviation of 46.5 m. With the increase of depths of hooks ,the proportion of swordfish in total catch increased to a maximum at the depth of 220 m to 250 m and then decreased. The proportion of female swordfish in catch increased with depths of hooks and then remained stable. The mean fork length of swordfish tended to increase with depths of hooks. This paper provided important information for improving our understanding of swordfish habitats and bycatch mitigation in the pelagic tuna fisheries.