The timing of anadromous migrations varies greatly among species, reflecting foraging opportunities, predation risk, and physical factors in freshwater and marine habitats. We studied the timing of bull trout, Salvelinus. confluentus, migrations downstream into Puget Sound, Washington, and the return migration using data from a combination of traps and beach seining to capture juveniles and adults, and acoustic telemetry to quantify movements in river, estuary, and marine waters. The period of marine residence overlapped among fish from different river basins and was generally brief; most bull trout entered marine waters from April to June and migrated back into rivers by July and August as temperatures were increasing, despite the increasing availability of prey fishes. The timing of return migration upriver occurred earlier in rivers with warmer temperatures than in cooler rivers, such that the fish entered at similar temperatures but different dates. However, the trapping and acoustic tag detections indicated that some exceptions occur, as individuals were in marine waters at times of the year when most of their populations were upriver. These timing patterns and other complex migration pathways and life history patterns indicated by the combination of sampling techniques, revealed the diversity in migratory behavior in this species, and the connections to the region’s abiotic and biotic conditions.

不同物种之间溯河迁徙的时间差异很大，反映了淡水和海洋栖息地的觅食机会、捕食风险和物理因素。我们研究了牛鳟鱼Salvelinus 的时间。汇合，向下游迁移到华盛顿州普吉特湾，以及使用来自陷阱和海滩围网的数据来捕获幼鱼和成鱼的数据返回迁移，以及声学遥测来量化河流、河口和海水中的运动。不同流域鱼类的海洋栖息期重叠，普遍较短；大多数牛鳟鱼在 4 月至 6 月进入海水，并在 7 月和 8 月随着气温升高而迁回河流，尽管猎物鱼的供应量增加。在温度较高的河流中，返回上游的时间比在凉爽的河流中发生得更早，因此鱼类进入的温度相似，但日期不同。然而，诱捕和声学标签检测表明发生了一些异常，因为人们在一年中大部分人口都在上游的时候都在海水中。这些时间模式和其他复杂的迁徙途径和生活史模式由采样技术的组合表明，揭示了该物种迁徙行为的多样性，以及与该地区非生物和生物条件的联系。