<b>TO BE ADDED</b>

1. Most reef fishes possess an early pelagic stage that ensures the crucial role of maintaining genetic connectivity between distant populations, as movements of older demersal stages are generally restricted. While classically considered passive, numerous studies show that most larvae/juveniles largely influence dispersion scale and settlement rate by actively swimming horizontally/vertically in an oriented way during most of their pelagic phase.2. Laboratory measurements of active dispersal skills differ from natural behaviors of individuals observed <i>in situ</i> by divers manually annotating depth and bearing every 30s, while carrying a low-speed flowmeter to estimate average speed. Here, we improved this protocol through the use of electronic measurement devices to achieve enhanced feasibility, replicability, efficiency, and safety. Bearing and depth could be precisely measured at high-frequencies using a logger fixed on an optimized diving tray, which allowed us to reduce tracking duration from 10 min to 5 min, to track more individuals. All further steps, including data entry, precise sensor calibration, circular statistical tests, and 3D track reconstruction using a Madwick filter, were automated within interactive pipelines, enabling to obtain results in the field within 3h after dives.3. To test our automated protocol, we conducted <i>in situ</i> trackings for a diversified set of species (32 per ocean) during developments in the Caribbean (Guadeloupe), before being routinely applied in the Indian Ocean (Maldives) with a high success rate (77%) despite offshore conditions. High individual orientation accuracy, combined with great swimming/sinking abilities dependent on depth/current, suggests that pelagic larvae and juveniles can swim in a correlated random-walk (CRW). This occurs even when orientation cues are too scarce for a consistent orientation among species/zones to emerge (biased CRW), marking a difference with their behavior in coastal environment.4. Although biophysical models of dispersal ease the development of informed conservation strategies at large spatial scales, comparisons with genetic connectivity demonstrate that only models incorporating realistic active behaviors yield comparable outputs. Our methodological advances overcome various obstacles preventing measuring the parameters necessary for active models, not only for tropical reef fishes, but also for any small pelagic organism in any aquatic habitat.1. 绝大多数礁栖鱼类拥有早期浮游阶段，该阶段对维持不同种群间的遗传连通性发挥关键作用，因为成体底栖阶段的活动范围通常受限。过往研究普遍认为该过程为被动扩散，但大量研究表明，多数鱼类幼体与稚鱼在多数浮游期内，会通过定向的水平/垂直主动游泳行为，显著影响扩散尺度与定居率。 2. 实验室测得的主动扩散能力，与潜水员每30秒手动标注深度、方位角，并携带低速流速计估算平均游速时，原位（in situ）观测到的个体自然行为存在差异。本研究对该实验方案进行优化，采用电子测量设备以提升实验的可行性、可重复性、效率与安全性。通过固定于优化型潜水托盘的记录装置，可高频精准测量方位角与深度，将单条轨迹的追踪时长从10分钟缩短至5分钟，从而能够追踪更多个体。其余所有流程，包括数据录入、传感器精准校准、圆形统计检验，以及使用Madwick滤波（Madwick filter）进行三维轨迹重构，均通过交互式工作流实现自动化，使研究人员可在潜水结束后3小时内于野外获取实验结果。 3. 为验证这套自动化实验方案，研究团队在加勒比海（瓜德罗普岛）海域开展了针对多类物种类群（每个大洋32个物种）的原位追踪实验，随后将方案常规应用于印度洋（马尔代夫）海域，尽管面临远海作业条件，仍取得了77%的高成功率。研究发现，个体的定向精度极高，且游泳与下沉能力随深度与海流条件发生显著变化，这表明浮游幼体与稚鱼可采用关联随机游走（correlated random-walk, CRW）模式运动。即便在定向线索匮乏、无法形成物种/区域间一致性定向的场景下，该行为模式仍会出现（即偏倚关联随机游走），这与它们在近岸环境中的行为存在显著差异。 4. 尽管生物物理模型（biophysical models）能够助力制定大空间尺度下的科学有据的保护策略，但将其与遗传连通性实测数据对比后可发现，仅当模型纳入真实的主动行为模式时，其输出结果才具备实际参考价值。本研究的方法学进展突破了多项此前阻碍获取主动扩散模型所需参数的障碍，该方法不仅适用于热带礁栖鱼类，也可推广至任意水生栖息地中的小型浮游生物。