Within the Gulf of Aden, Djibouti is an important site where whale sharks (Rhincodon typus Smith 1828) aggregate seasonally; however, up to now, only few studies have been carried out in the area (Rowat et al. in Environ Biol Fishes, 2007. https://doi.org/10.1007/s10641-006-9148-7; Mar Freshw Res, 2011. https://doi.org/10.1071/MF10135; Rezzolla and Storai in Cybium 34:195–206, 2010). From 2015 to 2018, whale shark photo-id, skin biopsies, and zooplankton samples were collected to investigate the ecology of this species in Djibouti. Of the 190 photo-identified individuals, the majority were juvenile males, confirming a significant male-based aggregation (X² = 65, df = 1, p < 0.0001). Within each season, the maximum number of times an individual was re-sighted was 11, while the inter-annual re-sighting rates varied between 11 and 32%. Animals were feeding on surface zooplankton, consisting primarily of copepods (85%); however, Chaetognatha and Ctenophora appeared to be important taxa as well, since the areas most visited were also those with higher concentration of these organisms. Feeding zooplankton patches had a mean biomass of 42.2 ± 31.9 mg m⁻³, almost 1.5 higher than control stations, indicating that the abundance of this species was positively related to food availability. Furthermore, whale sharks exhibited a clear temporal distribution associated with the variation in zooplankton biomass due to the monsoon winds. Sharks aggregated in October–February, with a peak in sightings in November, and dispersed outside the upwelling season. δ¹³C values suggested that whale sharks might migrate to other habitats or shift their activities to deeper areas outside the aggregation phase. Little intra-specific variation in δ¹⁵N and δ¹³C was found between animals, suggesting a similar habitat use.

中文翻译：

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吉布提的鲸鲨生态

在亚丁湾内，吉布提是重要的地点，鲸鲨（Rhincodon typus Smith 1828）季节性聚集。但是，到目前为止，在该地区仅进行了很少的研究（Rowat等人，在Environ Biol Fishes，2007年。https：//doi.org/10.1007/s10641-006-9148-7； Mar Freshw Res， 2011. https://doi.org/10.1071/MF10135; Rezzolla和Storai在Cybium 34：195–206，2010）。从2015年到2018年，收集了鲸鲨的光身份证，皮肤活检和浮游动物样本，以调查吉布提该物种的生态。在190位经过照片识别的个体中，大多数是未成年男性，这证实了明显的男性聚集（X ²  = 65，df  = 1，p <0.0001）。在每个季节内，对个人进行重新视听的最大次数为11次，而年间重新视听率的范围在11％至32％之间。动物以浮游动物为食，浮游动物主要由co足类（85％）组成。但是，Chaetognatha和Ctenophora似乎也很重要，因为访问最多的地区也是这些生物的集中地区。摄食浮游动物斑块的平均生物量为42.2±31.9 mg m ^-3，比控制站高出近1.5，表明该物种的丰富程度与粮食供应量呈正相关。此外，鲸鲨显示出明显的时间分布，这与由于季风引起的浮游生物量的变化有关。鲨鱼在10月至2月聚集，11月见顶高峰，并在上升季节之外散布。δ ¹³ C值表明，鲸鲨可能会迁移到其他栖息地或他们的活动转移到更深的领域聚集阶段之外。在δ特定帧内偏差小¹⁵ N和δ ¹³ ℃下的动物之间发现，这表明了类似的栖息地利用。