Upper trophic level predators dramatically impacted by fisheries include the large-bodied hammerhead sharks, which have become species of conservation concern worldwide. Implementing spatial management for conservation of hammerhead populations requires knowledge of temporal distribution patterns and habitat use, identification of essential habitat for protection, and quantification of interactions with human activities. There is little such information for the smooth hammerhead shark, Sphyrna zygaena. We used fin-mounted satellite tags to examine the movements and habitat use of juvenile smooth hammerheads, a demographic segment particularly threatened by exploitation. Six sharks were tagged off the US mid-Atlantic and tracked for 49–441 days (mean 187 ± 136 days). Sharks consistently showed area-restricted movements within a summer core area in waters of the New York Bight and a winter core area off Cape Hatteras, North Carolina, with directed movements between them in autumn. There was high overlap of shark winter core area use and the Mid-Atlantic Shark Area (MASA) – a 7 month per year, bottom-longline fishery closure – indicating that this area closure offers seasonal reduction in fishing pressure for this species. Based on timing of shark movements and the MASA closure, protection for juvenile smooth hammerheads may be increased by beginning the closure period 1 month earlier than currently scheduled. Generalized additive mixed models revealed that area-restricted movements of sharks in their summer and winter core areas coincided with high primary productivity, and elevated sea surface temperature. Consistency in use of summer and winter core areas suggests that the coastal waters of the New York Bight and Cape Hatteras, North Carolina could be considered for Essential Fish Habitat designation for this species. This study reveals the first high resolution movements and habitat use for smooth hammerheads in the western North Atlantic to inform management planning for this population.

中文翻译：

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北大西洋西部幼年平滑锤头鲨的季节性运动和栖息地利用及其管理意义

受渔业严重影响的上营养级食肉动物包括体型较大的双髻鲨，它们已成为世界范围内受到保护的物种。为保护双髻鲨种群实施空间管理需要了解时间分布模式和栖息地利用、确定保护的基本栖息地以及量化与人类活动的相互作用。光滑的双髻鲨 Sphyrna zygaena 几乎没有这样的信息。我们使用安装在鳍上的卫星标签来检查幼年光滑锤头鲨的运动和栖息地使用，这是一个特别受到剥削威胁的人口群体。六条鲨鱼在美国大西洋中部被标记并追踪了 49-441 天（平均 187 ± 136 天）。鲨鱼在纽约湾水域的夏季核心区域和北卡罗来纳州哈特拉斯角附近的冬季核心区域内一直表现出区域限制运动，秋季在它们之间进行定向运动。鲨鱼冬季核心区的使用与中大西洋鲨鱼区 (MASA) 的高度重叠 - 每年 7 个月，底延绳钓渔业关闭 - 表明该区域关闭为该物种的捕捞压力提供了季节性减少。根据鲨鱼移动的时间和 MASA 关闭，可以通过比当前计划提前 1 个月开始关闭期来增加对幼年光滑双髻鲨的保护。广义加性混合模型表明，鲨鱼在夏季和冬季核心区的区域限制运动与高初级生产力和海面温度升高相吻合。夏季和冬季核心区使用的一致性表明，纽约湾和北卡罗来纳州哈特拉斯角的沿海水域可以考虑作为该物种的基本鱼类栖息地指定。这项研究揭示了北大西洋西部光滑锤头鲨的首次高分辨率运动和栖息地用途，可为该种群的管理规划提供信息。