ABSTRACT: Understanding how reef-associated sharks utilise coastal reef habitats throughout their ontogeny is essential for their effective management. In this study, we assessed the distribution of sharks in the northern Caribbean Netherlands (Saba, Saba Bank and St Eustatius) and ontogenetic shifts in habitat and depth use of the 2 most observed species: Caribbean reef shark Carcharhinus perezi and nurse shark Ginglymostoma cirratum. We used stereo baited remote underwater video (stereo-BRUV) surveys at 376 sites. A total of 126 shark sightings (6 species) were recorded, with C. perezi (n = 72) and G. cirratum (n = 42) most frequently observed. The probability of recording at least 1 shark per deployment ranged from 0.19 to 0.37 and is comparable with shark occurrences in the small number of other stereo-BRUV studies in the Wider Caribbean Region. Habitat type was the most important factor driving reef-associated shark occurrences, with the highest probability of observing C. perezi and G. cirratum in soft-coral habitat. Additionally, occurrences of C. perezi were significantly influenced by the management zone, with highest probabilities of occurrence in no-fishing zones. Almost all observed reef-associated sharks (95.6%) were juveniles, indicating that the study area may be a nursery area. Overall, both species were observed in deeper waters with increasing size, indicating ontogenetic shifts in depth use. Our findings imply that protected areas should not be limited to a single habitat or depth, but focus on protecting a large area with the range of habitats and depths necessary for reef-associated sharks to complete their life cycle.

中文翻译：

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加勒比海东北部与礁相关的鲨鱼种类的分布及其成因的生境变化

摘要：了解与礁石相关的鲨鱼如何在其整个个体发育过程中利用沿海礁石栖息地，对于其有效管理至关重要。在这项研究中，我们评估了鲨鱼在荷兰北部加勒比海地区（萨巴岛，萨巴河岸和圣尤斯达西斯）的分布以及在生境上的遗传变化以及两种最常见物种的栖息地和深度利用：加勒比礁鲨Carcharhinus perezi和护士鲨Ginglymostoma cirratum。我们在376个地点使用了立体声诱饵远程水下视频（stereo-BRUV）调查。总共记录到126个鲨鱼目击者（6种），其中C. perezi（n = 72）和G. cirratum（n = 42）最常被观察到。每次部署记录至少1条鲨鱼的概率在0.19至0.37之间，与大加勒比地区少数其他立体BRUV研究中鲨鱼的发生率相当。栖息地类型是驱动与珊瑚礁相关的鲨鱼发生的最重要因素，在软珊瑚栖息地中观察到C. perezi和G. cirratum的可能性最高。此外，C。perezi的发生受到管理区的影响很大，在非捕捞区发生的可能性最高。几乎所有观察到的与礁石有关的鲨鱼（95.6％）都是幼鱼，这表明研究区域可能是苗圃区域。总体而言，在更深的水域中都发现了这两种物种，并且它们的大小不断增加，表明在深度利用中个体发育发生了变化。我们的发现表明，保护区不应局限于单一的栖息地或深度，而应重点保护具有与珊瑚礁相关的鲨鱼完成其生命周期所必需的栖息地和深度范围的大区域。