Harris Joanna L, Hosegood Phil, Robinson Edward, Embling Clare B, Hilbourne Simon, Stevens Guy M W
The Manta Trust Dorset UK.
School of Biological and Marine Sciences University of Plymouth Plymouth UK.
Ecol Evol. 2021 Mar 24;11(9):4588-4604. doi: 10.1002/ece3.7357. eCollection 2021 May.
Globally, reef manta rays () are in decline and are particularly vulnerable to exploitation and disturbance at aggregation sites. Here, passive acoustic telemetry and a suite of advanced oceanographic technologies were used for the first time to investigate the fine-scale (5-min) influence of oceanographic drivers on the visitation patterns of 19 tagged to a feeding aggregation site at Egmont Atoll in the Chagos Archipelago. Boosted regression trees indicate that tag detection probability increased with the intrusion of cold-water bores propagating up the atoll slope through the narrow lagoon inlet during flood tide, potentially transporting zooplankton from the thermocline. Tag detection probability also increased with warmer near-surface temperature close to low tide, with near-surface currents flowing offshore, and with high levels of backscatter (a proxy of zooplankton biomass). These combinations of processes support the proposition that zooplankton carried from the thermocline into the lagoon during the flood may be pumped back out through the narrow inlet during an ebb tide. These conditions provide temporally limited feeding opportunities for , which are tied on the tides. Results also provide some evidence of the presence of Langmuir Circulation, which transports and concentrates zooplankton, and may partly explain why occasionally remained at the feeding location for longer than that two hours. Identification of these correlations provides unique insight into the dynamic synthesis of fine-scale oceanographic processes which are likely to influence the foraging ecology of at Egmont Atoll, and elsewhere throughout their range.
在全球范围内，礁蝠鲼（Mobula alfredi）数量正在减少，并且在聚集地点特别容易受到开发和干扰。在此，首次使用被动声学遥测技术和一系列先进的海洋学技术，来研究海洋学驱动因素对19只带有标记的礁蝠鲼前往查戈斯群岛埃格蒙特环礁一个觅食聚集地点的访问模式的精细尺度（5分钟）影响。增强回归树分析表明，在涨潮期间，随着冷水涌升流通过狭窄的泻湖入口向上穿过环礁斜坡侵入，标记检测概率增加，这可能将浮游动物从温跃层输送过来。在接近低潮时，随着近表层温度升高、近表层海流向近海流动以及高后向散射水平（浮游动物生物量的一个指标），标记检测概率也会增加。这些过程的组合支持了这样一种观点，即涨潮期间从温跃层带入泻湖的浮游动物可能在落潮时通过狭窄入口被泵出。这些条件为与潮汐相关的礁蝠鲼提供了时间有限的觅食机会。研究结果还提供了一些朗缪尔环流存在的证据，朗缪尔环流能够运输和聚集浮游动物，这可能部分解释了为什么礁蝠鲼偶尔会在觅食地点停留超过两个小时。识别这些相关性为精细尺度海洋学过程的动态综合提供了独特见解，这些过程可能会影响埃格蒙特环礁以及其分布范围内其他地方的礁蝠鲼的觅食生态。
