Data_Sheet_1_Seasonal Occurrence, Horizontal Movements, and Habitat Use Patterns of Whale Sharks (Rhincodon typus) in the Gulf of Mexico.docx

In the northern Gulf of Mexico (GOM), whale sharks (Rhincodon typus) form large aggregations at continental shelf-edge banks during summer; however, knowledge of movements once they leave aggregation sites is limited. Here we report on the seasonal occurrence of whale sharks in the northern GOM based on over 800 whale shark sightings from 1989 to 2016, as well as the movements of 42 whale sharks tagged with satellite-linked and popup satellite archival transmitting tags from 2008 to 2015. Sightings data were most numerous during summer and fall often with aggregations of individuals reported along the continental shelf break. Most sharks (66%) were tagged during this time at Ewing Bank, a known aggregation site off the coast of Louisiana. Whale shark track duration ranged from three to 366 days and all tagged individuals, which ranged from 4.5 to 12.0 m in total length, remained within the GOM. Sightings data revealed that whale sharks occurred primarily in continental shelf and shelf-edge waters (81%) whereas tag data revealed the sharks primarily inhabited continental slope and open ocean waters (91%) of the GOM. Much of their time spent in open ocean waters was associated with the edge of the Loop Current and associated mesoscale eddies. During cooler months, there was a net movement southward, corresponding with the time of reduced sighting reports. Several sharks migrated to the southwest GOM during fall and winter, suggesting this region could be important overwintering habitat and possibly represents another seasonal aggregation site. The three long-term tracked whale sharks exhibited interannual site fidelity, returning one year later to the vicinity where they were originally tagged. The increased habitat use of north central GOM waters by whale sharks as summer foraging grounds and potential interannual site fidelity to Ewing Bank demonstrate the importance of this region for this species.

在墨西哥湾北部（Gulf of Mexico, GOM），鲸鲨（Rhincodon typus）于夏季在大陆架边缘浅滩形成大型聚集群，但目前学界对其离开聚集场所后的移动规律仍认知有限。本研究基于1989年至2016年间的800余条鲸鲨目击记录，以及2008年至2015年对42头搭载卫星链接式标记（satellite-linked tags）与弹出式卫星档案传输标记（popup satellite archival transmitting tags）的鲸鲨的移动轨迹分析，报道了墨西哥湾北部鲸鲨的季节分布特征。目击数据在夏季与秋季最为丰富，多数记录显示鲸鲨群聚集于大陆架坡折带沿线。其中66%的被标记个体于该时段在路易斯安那州外海的已知聚集点——尤因浅滩（Ewing Bank）完成标记。鲸鲨的追踪时长为3至366天不等，所有被标记个体的全长介于4.5至12.0米之间，且全程均停留于墨西哥湾海域。目击数据显示，81%的鲸鲨记录来自大陆架及架缘水域；而标记数据则表明，91%的鲸鲨栖息于墨西哥湾的大陆坡与公海水域。鲸鲨在公海水域的停留时段多与环流向（Loop Current）边缘及伴随的中尺度涡旋相关。在水温较低的月份，鲸鲨呈现整体向南移动的趋势，这与目击记录减少的时段相吻合。部分个体在秋季与冬季迁移至墨西哥湾西南部海域，表明该区域或为重要的越冬栖息地，亦可能是另一处季节性聚集点。三头长期追踪的鲸鲨表现出年际位点保真（interannual site fidelity）行为，即次年返回了初始标记点附近海域。鲸鲨将墨西哥湾中北部海域作为夏季觅食场的栖息地利用比例提升，加之其对尤因浅滩的潜在年际位点保真行为，均证明该区域对该物种的生态重要性。