Context: Over the past decade, the coastal waters off Cape Cod, Massachusetts, have emerged as the only known aggregation site for the white shark (Carcharodon carcharias) in the western North Atlantic. During periods of seasonal residency, white sharks patrol the shoreline in search of pinniped prey, bringing them in close proximity to popular beaches where people recreate.

Aim: To examine whether white sharks off Cape Cod are more likely to occupy shallow depths (and consequently more likely to overlap with recreational water users) under certain conditions.

Methods: We deployed short-term, pop-up satellite archival transmitting (PSAT) tags and acoustic transmitters on 14 subadult and adult white sharks off the coast of Cape Cod during the summer and fall of 2017. PSAT tags provided fine-scale depth and temperature data, which were combined with high-resolution location data obtained from an acoustic telemetry array, to identify the depth and temperature preferences of white sharks when resident in the area.

Key results: Sharks spent the majority (95%) of tracked time at depths of 0–31 m and at temperatures from 8.9°C to 20.7°C. During resident periods along Cape Cod, individuals spent almost half (47%) of their time at depths of less than 4.5 m, but made frequent excursions to mid-shelf depths, alternating between the surf zone and deeper offshore waters. Sharks were slightly more likely to occupy shallow depths at night during the new moon. The relationship between shark depth and lunar phase varied over the course of the day, suggesting the mechanism underlying lunar effects differs among diel periods.

Conclusions: Although the overall risk posed to humans by white sharks is low, there is a high potential for overlap between white sharks and recreational water users off Cape Cod. The risk of interaction may be slightly higher during periods when local environmental conditions favour the species’ predatory stealth by influencing prey behaviour or detectability.

Implications: This study provides the first glimpse into the fine-scale vertical habitat use of white sharks off Cape Cod, which can be used to better understand the risk to recreational water users and to inform public safety practices.

背景信息：过去十年来，马萨诸塞州科德角（Cape Cod）附近的沿海水域已成为北大西洋西部唯一已知的白鲨（Carcharodon carcharias）聚集地。在季节性居住期间，白鲨在海岸线上巡逻，寻找被夹住的猎物，使它们靠近人们重建的热门海滩。

目的：研究在某些条件下，科德角附近的白鲨是否更可能占据浅层深度（并因此更可能与休闲用水者重叠）。

方法： 2017年夏季和秋季，我们在科德角海岸附近的14个亚成年和成年白鲨中部署了短期弹出式卫星档案发射（PSAT）标签和声发射器。PSAT标签可提供精细的深度和深度。温度数据与从声遥测阵列获得的高分辨率位置数据相结合，以识别居住在该地区的白鲨的深度和温度偏好。

关键结果：鲨鱼在0-31 m的深度以及8.9°C至20.7°C的温度下花费了大部分（95％）的跟踪时间。在科德角（Cape Cod）沿岸居民期间，人们几乎将一半的时间（47％）花在4.5m以下的深度，但经常游览中层深度，在冲浪区和更深的近海水域之间交替。在新月的晚上，鲨鱼更可能占据浅水区。鲨鱼的深度与月相之间的关系在一天当中会有所不同，这表明在迪尔时期之间，影响月球影响的机制也不同。

结论：尽管白鲨对人类构成的总体风险较低，但在鳕鱼角附近，白鲨与娱乐用水者之间存在很大的重叠潜力。当当地环境条件通过影响猎物的行为或可检测性而有利于该物种的掠食性隐身时，相互作用的风险可能会稍高一些。

启示：这项研究首次揭示了鳕鱼角附近白鲨在垂直尺度上栖息地的精细利用，可用于更好地了解休闲用水者的风险并为公共安全实践提供信息。